Dual-power supply system of high-voltage box built-in battery and control method

Abstract

The invention relates to the technical field of dual power supplies, and discloses a dual power supply system for a high-voltage box built-in battery, and the system comprises an AC / DC main power module which is used for converting a single-phase AC 220V input into a DC 24V DC output; the DC battery pack is formed by connecting lithium iron phosphate cells in series; the input end of the DC / DC standby power module is connected with the DC battery pack, and the output end of the DC / DC standby power module provides 23V DC voltage; the intelligent switching unit comprises a reverse diode group connected in parallel between the main circuit and the standby circuit, and is used for blocking the standby loop when the main power supply is normal and conducting the standby power supply when the interruption of the main power supply is less than or equal to 3ms; a battery management communication interface; and a grading protection mechanism. According to the invention, the battery, the standby power supply and the switching logic are all integrated in the high-voltage box to form an integrated dual-power system, external links such as an alternating-current cable, an air switch and an adapter between the UPS and the high-voltage box are thoroughly cancelled, and the reliability of the system is upgraded from a series structure to a parallel redundant structure.

Description

Technical Field

[0001] The present invention relates to the technical field of dual power supplies, and in particular to a dual power supply system with a high-voltage box having built-in batteries and a control method thereof. Background Art

[0002] In application scenarios such as rail transit, data centers, and photovoltaic energy storage, high-voltage DC distribution systems ensure that critical loads such as control and communication can continue to operate during mains power outages. Traditionally, one or more uninterruptible power supplies (UPSs) are connected in parallel outside the high-voltage box. UPSs typically consist of a rectifier, inverter, and lead-acid battery pack, and continue to provide power through "AC-DC-AC" dual conversion when the mains power is abnormal.

[0003] After searching, the Chinese patent number CN104102260B discloses a dual power supply system, which includes a voltage comparator and a low-voltage difference linear regulator. The voltage comparator generates a control signal based on the comparison result of the first power supply and the second power supply, and the low-voltage difference linear regulator performs low-voltage difference linear regulation on the first power supply and / or the second power supply according to the control signal. The low-voltage difference linear regulator includes a first transistor, a second transistor, a first switch, a current mirror circuit and a voltage stabilization circuit. When the voltage comparator outputs a control signal to control the connection between the active end of the first switch and the second fixed end of the first switch, the first transistor is turned on under the action of the current mirror circuit and the second voltage, and the second transistor is turned on under the action of the bias voltage generated by the first transistor.

[0004] After searching, the Chinese patent number CN111327106A discloses a dual-power automatic switching power supply system, including a high-voltage side power supply line and a low-voltage side power supply line. The low-voltage side power supply line includes a company power load line and a key equipment power load line. The company power load line is connected to the high-voltage side power supply line through a transformer; the company power load line is connected to the transformer through a transfer switch, and the transfer switch is also connected to a backup generator; after the transfer switch detects the transformer power-off signal, it controls the generator to start and supply power to the key equipment power load line; this improves the current situation where key equipment cannot quickly switch to the backup motor line when the power is off.

[0005] However, as an independent device, the UPS requires additional AC input and output cables, circuit breakers, and communication interfaces between it and the high-voltage box, forming a two-level "UPS + high-voltage box" architecture. Failure in any link may cause the entire system to shut down. However, due to the influence of UPS detection and relay action, the switching time from mains power failure to UPS inverter output is usually 10ms-20ms, which cannot meet the needs of loads with higher requirements for power supply continuity. Based on this, the present invention designs a dual-power supply system with a built-in battery in the high-voltage box and a control method to solve the above problems. Summary of the Invention

[0006] The purpose of the present invention is to provide a dual power supply system with a high-voltage box and a built-in battery and a control method, which solves the problems of system shutdown and inability to meet higher loads in the background technology.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0008] A dual power supply system with a high-voltage box and built-in batteries, comprising:

[0009] AC / DC main power supply module, used to convert single-phase AC220V input into DC24V output;

[0010] DC battery pack, composed of lithium iron phosphate cells connected in series;

[0011] A DC / DC backup power supply module, the input end of which is connected to the DC battery pack and the output end of which provides a 23V DC voltage;

[0012] Intelligent switching unit, including a reverse diode group connected in parallel between the main and backup circuits, used to block the backup circuit when the main power supply is normal, and turn on the backup power supply within ≤3ms when the main power supply is interrupted;

[0013] Battery management communication interface, obtains battery pack SOC, SOH and temperature data through CAN bus;

[0014] Hierarchical protection agencies, including:

[0015] The first circuit breaker is equipped with shunt trip coils F11-F27, which cut off non-critical loads when the SOC is less than 5%.

[0016] The second circuit breaker is equipped with shunt trip coils F12-F28, which disconnect the main circuit when the single-cell voltage is less than 2.5V.

[0017] Preferably, the DC battery pack has a capacity of ≥10 kWh, is integrated into an independent sealed cavity in the high-voltage box, and is physically isolated from the low-voltage control area by an insulating partition with a voltage resistance of ≥3 kV.

[0018] Preferably, the DC / DC backup power supply module adopts a high-efficiency step-down circuit with a wide voltage input range, an output voltage of 23V and a peak power ≥500W.

[0019] Preferably, the reverse diode group adopts a silicon carbide Schottky diode array, the reverse recovery time of which is ≤50ns and the forward conduction voltage drop is ≤1.5V.

[0020] Preferably, the hierarchical protection mechanism further includes:

[0021] The third circuit breaker is equipped with shunt trip coils F13-F29. It cuts off the battery charging circuit when the response temperature is greater than 65°C or the temperature difference between adjacent sensors is greater than 15°C, and automatically resets when the temperature is less than 50°C.

[0022] The fourth circuit breaker is equipped with shunt trip coils F14-F30. When the insulation monitoring resistance is less than 500kΩ, it disconnects the high-voltage bus and reports the fault code 0x18FEFE02 through the CAN bus.

[0023] The fifth circuit breaker is equipped with shunt trip coils F15-F31. It cuts off the battery output within 5ms in response to the opening of the high-voltage interlock circuit or the displacement of the partition greater than 2mm. It needs to be manually reset after the fault is eliminated.

[0024] The third circuit breaker F29 uses dual MOSFET redundancy in the coil drive circuit, which can still trip even if a single tube is short-circuited. The temperature sensors are arranged at the geometric center and edge of the battery module to form a 3D temperature field to prevent local overheating.

[0025] The fourth circuit breaker F30 uses a low-frequency square wave injection method for insulation monitoring to avoid the influence of busbar capacitance, with a detection accuracy of ±5%. The fault code 0x18FEFE02 contains the insulation resistance value and polarity information, which facilitates operation and maintenance positioning.

[0026] The fifth circuit breaker F31, the high-voltage interlock circuit is connected in series with all covers and plugs. It will be triggered if any point is disconnected. To reset it, you need to eliminate the fault first, then turn the key switch to reset to prevent power on with a fault.

[0027] The above technical solution shows that after the system is powered on, AC220V is first converted to DC24V via the AC / DC main power module, which then supplies power to all low-voltage control units in the high-voltage box. Simultaneously, the output of the AC / DC module is connected in parallel with the output of the DC / DC backup power module via a set of silicon carbide Schottky reverse diode arrays. Because the diode array exhibits a near-zero resistance characteristic under forward voltage drop, when the AC / DC output voltage is higher than the DC / DC output voltage, the diodes naturally cut off, blocking the backup circuit and placing the system in the main power supply state. At this point, the DC / DC module is in "hot standby" mode, maintaining only low-power operation (<5W) for the internal control circuits. It also reads the SOC, SOH, and multi-point temperature information of the DC1500V lithium iron phosphate battery pack via the CAN bus cycle, providing predictive data for subsequent switching actions.

[0028] When the AC input voltage drops below a set threshold (typically 198V), the AC / DC module output voltage decreases simultaneously. Once this voltage falls below the DC / DC backup output voltage of 23V, the silicon carbide Schottky diode array transitions from cutoff to conduction within a reverse recovery time of ≤50ns, allowing the backup power supply to instantly take over the entire load current. During this switching period, the DC / DC module internally employs a voltage feedforward + current closed-loop PWM control strategy, dynamically adjusting the duty cycle based on the SOC to ensure output voltage fluctuations are suppressed to within 23V±1%, achieving "zero-perception" seamless switching in ≤3ms.

[0029] According to a second aspect of the present invention, a method for controlling dual power supply of a high-voltage box with a built-in battery is also provided, comprising the following steps:

[0030] Step S1: monitor the main power supply voltage in real time. When the voltage is lower than the threshold, switch to the backup power supply within ≤3ms, and control the output voltage fluctuation within 23V±5% during the switching process.

[0031] Step S2, periodically reading the battery pack SOC, SOH and temperature data, and adjusting them according to the intelligent switching unit;

[0032] Step S3: When the SOC is less than 5%, a shutdown command is sent to the inverter and the first circuit breaker is triggered;

[0033] Step S4: When SOC=0% or the cell voltage is less than 2.5V, trigger the second circuit breaker.

[0034] Preferably, the AC / DC main power supply module has input overvoltage, undervoltage and phase loss protection, with thresholds set to AC275V and AC165V respectively, and an action time of ≤50ms; output overcurrent, short circuit and reverse connection protection, with an overcurrent threshold of 120% of the rated current and a recovery time of ≤500ms; output voltage temperature compensation function, with a compensation coefficient of -3mV / ℃ / cell, ensuring an output accuracy of ±2% in the range of -40℃ to +85℃.

[0035] Preferably, the DC / DC backup power supply module dynamically adjusts the PWM duty cycle according to the SOC to stabilize the output voltage;

[0036] The DC / DC backup power supply module also includes:

[0037] Input pre-charge circuit, pre-charge current ≤ 0.05C, pre-charge time 2s-5s adjustable to prevent power-on shock;

[0038] Output current sharing bus, supports parallel connection of up to 8 modules, with current sharing accuracy of ±5%;

[0039] Output voltage soft-start function, with a configurable startup slope of 0.5V / ms-5V / ms, suppresses inrush current.

[0040] The above technical solution demonstrates that during the backup power supply phase, the high-efficiency DC / DC step-down circuit converts the 1500V bus voltage through a two-stage three-level LLC resonant stage and a synchronous rectification stage, achieving an efficiency exceeding 96%, continuously delivering 500W peak power to critical loads. The battery management unit monitors the temperature of each module in real time via a distributed temperature sensor network. When the temperature difference between adjacent sensors exceeds 15°C, the high-voltage box's built-in centrifugal air cooling unit is activated, forcing air cooling to maintain the battery cell temperature within a safe range of 0°C to 45°C. Thermal events are also reported to the BMS.

[0041] When the BMS detects that the SOC is less than 5%, it broadcasts a shutdown command to the inverter via the CAN bus and activates the first circuit breaker's shunt trip coils F11-F27 within 20ms, disconnecting non-critical loads and maintaining only the RCUs (≤10W) at minimum power consumption. If discharge continues until the SOC reaches 0% or the voltage of any cell falls below 2.5V, the second circuit breaker's shunt trip coils F12-F28 activate within the same timeframe, completely disconnecting the 1500V busbar and preventing battery over-discharge. Both circuit breakers feature arc magnetic blowout and gas-assisted arc extinguishing, ensuring reliable disconnection under DC1500V / 50A operating conditions.

[0042] Preferably, the intelligent switching unit further includes:

[0043] Redundant reverse diode group, connected in parallel with the main diode group, automatically switches when a single group fails, with a switching time of ≤100ns;

[0044] The diode temperature monitoring circuit triggers derating output and reports a fault when the junction temperature is greater than 125°C;

[0045] The switching status indicator uses a dual-color LED, green for the main supply and red for the backup supply, which flashes synchronously when switching at a frequency of 1Hz.

[0046] Preferably, the battery management communication interface further includes:

[0047] Redundant CAN bus, baud rate adjustable from 125kbps to 1Mbps, supports J1939 protocol;

[0048] Remote upgrade interface, compatible with ISO15765-2 diagnostic specification, upgrade time <5min, power-off resume;

[0049] Independent pressure relief channel, bursting pressure ≤ 50kPa and channel area ≥ 2000mm 2 ;

[0050] Double-layer shielding structure, inner layer 0.8mm galvanized steel and outer layer 1.5mm aluminum alloy.

[0051] The above technical solution demonstrates that after the main power supply is restored, the system delays 5-10 seconds to verify the slope and stability of the AC / DC output voltage. Once stability is confirmed, the DC / DC module PWM drive is first shut off. Once the output voltage drops to at least 2V below the AC / DC output, the reverse diode array is cut off again, allowing the load to return to the main power supply without disturbance. The entire switchback process is monitored in real time by a high-voltage interlock circuit. If a loose high-voltage connector or displaced insulating barrier is detected, the interlock signal triggers the battery-side relay to disconnect within 5ms and reports a fault code, ensuring personal and equipment safety.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] 1. This invention integrates the battery, backup power supply, and switching logic into the high-voltage box to form an integrated dual power supply system. This completely eliminates external links such as AC cables, circuit breakers, and adapters between the UPS and the high-voltage box. The system reliability is upgraded from a series structure to a parallel redundant structure, reducing the probability of overall downtime due to failure of intermediate links.

[0054] 2. The present invention uses an intelligent switching unit composed of a built-in silicon carbide Schottky diode array to achieve millisecond-level seamless switching after the main power supply is lost. The closed-loop voltage stabilization technology compresses the output voltage fluctuation to an extremely small range, ensuring uninterrupted operation of sensitive loads and solving the switching delay and voltage drop problems of traditional UPS.

[0055] 3. The present invention encapsulates the battery pack and all backup power modules inside the high-voltage box, retaining only the original AC input interface. No external UPS cabinet and supporting wiring are required, significantly reducing on-site installation space and wiring workload, and achieving a compact design. Through the built-in battery management communication interface, the battery charge status, health status and temperature information are obtained in real time, and a hierarchical protection strategy is implemented based on the status information, cutting off non-critical loads in advance or completely isolating the battery, solving the battery over-discharge problem caused by information loss in traditional UPS. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 This is a system architecture diagram of the present invention;

[0057] Figure 2 This is a schematic diagram of the intelligent switching principle of the present invention;

[0058] Figure 3 This is a logic flow chart of hierarchical protection of the present invention;

[0059] Figure 4 This is a flow chart of the control method of the present invention. DETAILED DESCRIPTION

[0060] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0061] Example 1;

[0062] See also Figures 1-4 In an embodiment of the present invention, a dual power supply system with a high-voltage box and a built-in battery includes:

[0063] AC / DC main power supply module, used to convert single-phase AC220V input into DC24V output;

[0064] DC battery pack, composed of lithium iron phosphate cells connected in series;

[0065] DC / DC backup power module, the input end is connected to the DC battery pack, and the output end provides 23V DC voltage;

[0066] Intelligent switching unit, including a reverse diode group connected in parallel between the main and backup circuits, used to block the backup circuit when the main power supply is normal, and turn on the backup power supply within ≤3ms when the main power supply is interrupted;

[0067] Battery management communication interface, obtains battery pack SOC, SOH and temperature data through CAN bus;

[0068] Hierarchical protection agencies, including:

[0069] The first circuit breaker is equipped with shunt trip coils F11-F27, which cut off non-critical loads when the SOC is less than 5%.

[0070] The second circuit breaker is equipped with shunt trip coils F12-F28, which disconnect the main circuit when the single-cell voltage is less than 2.5V.

[0071] The DC battery pack has a capacity of ≥10kWh and is integrated into an independent sealed cavity in the high-voltage box. It is physically isolated from the low-voltage control area by an insulating partition with a voltage resistance of ≥3kV.

[0072] The DC / DC backup power module adopts a high-efficiency step-down circuit with a wide voltage input range, an output voltage of 23V and a peak power ≥500W.

[0073] The reverse diode group uses a silicon carbide Schottky diode array with a reverse recovery time of ≤50ns and a forward voltage drop of ≤1.5V.

[0074] The hierarchical protection agencies also include:

[0075] The third circuit breaker is equipped with shunt trip coils F13-F29. It cuts off the battery charging circuit when the response temperature is greater than 65°C or the temperature difference between adjacent sensors is greater than 15°C, and automatically resets when the temperature is less than 50°C.

[0076] The fourth circuit breaker is equipped with shunt trip coils F14-F30. When the insulation monitoring resistance is less than 500kΩ, it disconnects the high-voltage bus and reports the fault code 0x18FEFE02 through the CAN bus.

[0077] The fifth circuit breaker is equipped with shunt trip coils F15-F31. It cuts off the battery output within 5ms in response to the opening of the high-voltage interlock circuit or the displacement of the partition greater than 2mm. It needs to be manually reset after the fault is eliminated.

[0078] The working principle of the embodiment of the present invention is as follows: after the system is powered on, the main power supply path is immediately established, and the AC voltage is rectified and isolated to form a stable low-voltage DC bus, which supplies power to all control units inside the high-voltage box. The output end of the backup power supply connected in parallel with the bus is reversely isolated by a unidirectional conductive device; in the range where the main power supply voltage is higher than the backup power supply voltage, the unidirectional device is in the cut-off state, the backup power supply does not provide energy to the load, and only maintains its internal control circuit in a low-power standby state, while periodically evaluating the status of the energy storage battery.

[0079] When the main power supply voltage is detected to drop below the threshold, the bus voltage drops accordingly, the potential relationship at both ends of the single-phase device is reversed, the backup power supply is turned on within nanoseconds, and the backup energy takes over all load currents without delay; during the switching period, the backup power supply adopts closed-loop regulation to correct the output in real time according to the charge state of the energy storage unit, so that the voltage fluctuation at the load end is compressed to within 1% of the rated range, achieving a seamless transition.

[0080] During backup power supply, the energy storage unit delivers continuous power through a highly efficient DC conversion process. This process maintains high conversion efficiency across a wide input voltage range and minimizes energy loss. The system also monitors battery temperature distribution. When the temperature difference exceeds a set limit, the air cooling device is triggered, bringing the temperature back to a safe operating range through forced convection.

[0081] When the battery energy drops to the first warning level, the system immediately broadcasts a power reduction or shutdown command to external electrical equipment and disconnects non-critical loads, retaining only the minimum power consumption required to maintain necessary monitoring; if the battery energy further decays to the second warning level or the voltage of any single cell falls below the lower limit, the system performs a final power-off action, completely cutting off the connection between the energy storage unit and the external circuit to avoid deep discharge.

[0082] Once the main power supply is restored, the system first double-confirms the slope and voltage regulation of the input voltage, and then shuts down the backup power supply output stage after a delay of several seconds. When the terminal voltage drops below a certain value of the main power supply, the single-phase device is naturally cut off, and the load returns to the main power supply without disturbance. During this process, the high-voltage interlock circuit detects the integrity of all high-voltage interfaces and insulation barriers in real time. Any abnormality will trigger an instantaneous power outage and report fault information to ensure the safety of personnel and equipment.

[0083] Example 2;

[0084] See also Figures 1-4 In an embodiment of the present invention, a method for controlling dual power supply of a high-voltage box with built-in batteries includes the following steps:

[0085] Step S1: monitor the main power supply voltage in real time. When the voltage is lower than the threshold, switch to the backup power supply within ≤3ms, and control the output voltage fluctuation within 23V±5% during the switching process.

[0086] Step S2, periodically reading the battery pack SOC, SOH and temperature data, and adjusting them according to the intelligent switching unit;

[0087] Step S3: When the SOC is less than 5%, a shutdown command is sent to the inverter and the first circuit breaker is triggered;

[0088] Step S4: When SOC=0% or the cell voltage is less than 2.5V, trigger the second circuit breaker.

[0089] The AC / DC main power module features input overvoltage, undervoltage, and phase loss protection, with thresholds set at AC275V and AC165V, respectively, and an activation time of ≤50ms. It also features output overcurrent, short-circuit, and reverse polarity protection, with an overcurrent threshold of 120% of the rated current and a recovery time of ≤500ms. It also features output voltage temperature compensation with a coefficient of -3mV / °C / cell, ensuring an output accuracy of ±2% within the -40°C to +85°C range.

[0090] The DC / DC backup power module dynamically adjusts the PWM duty cycle according to the SOC to stabilize the output voltage;

[0091] The DC / DC backup power module also includes:

[0092] Input pre-charge circuit, pre-charge current ≤ 0.05C, pre-charge time 2s-5s adjustable to prevent power-on shock;

[0093] Output current sharing bus, supports parallel connection of up to 8 modules, with current sharing accuracy of ±5%;

[0094] Output voltage soft-start function, with a configurable startup slope of 0.5V / ms-5V / ms, suppresses inrush current.

[0095] The intelligent switching unit also includes:

[0096] Redundant reverse diode group, connected in parallel with the main diode group, automatically switches when a single group fails, with a switching time of ≤100ns;

[0097] The diode temperature monitoring circuit triggers derating output and reports a fault when the junction temperature is greater than 125°C;

[0098] The switching status indicator uses a dual-color LED, green for the main supply and red for the backup supply, which flashes synchronously when switching at a frequency of 1Hz.

[0099] The battery management communication interface also includes:

[0100] Redundant CAN bus, baud rate adjustable from 125kbps to 1Mbps, supports J1939 protocol;

[0101] Remote upgrade interface, compatible with ISO15765-2 diagnostic specification, upgrade time <5min, power-off resume;

[0102] Independent pressure relief channel, bursting pressure ≤ 50kPa and channel area ≥ 2000mm 2 ;

[0103] Double-layer shielding structure, inner layer 0.8mm galvanized steel and outer layer 1.5mm aluminum alloy.

[0104] The working principle of the embodiment of the present invention is: when the system is running, the main power supply continuously provides energy to the load, and at the same time periodically obtains the charge state, health status and temperature distribution data of the energy storage unit through the communication bus; the backup power supply control logic is in the monitoring and calculation state and does not output power.

[0105] When the monitoring algorithm determines that the main power supply voltage or frequency is abnormal and continues to exceed the set time window, the control logic immediately activates the backup power supply output stage; due to the instantaneous reversal of the potential relationship between the two ends of the unidirectional conducting device, the backup power supply is turned on within a microsecond time scale, and the load current transitions smoothly. During the transition period, the output voltage is closed-loop regulated and maintained within a high-precision range of the rated value, achieving imperceptible power supply switching.

[0106] After entering the backup power supply stage, the control logic dynamically adjusts the modulation parameters of the DC conversion link according to the real-time state of charge to maintain high-efficiency energy transfer; at the same time, the temperature monitoring network continuously calculates the spatial temperature gradient. When the local temperature difference exceeds the set threshold, the cooling strategy is triggered to suppress thermal imbalance through forced convection.

[0107] As discharge progresses, if the state of charge drops to the first threshold, the control logic first sends a load reduction command to the external power conversion device, and then drives the first-level circuit breaker to open, retaining only the minimum power path to maintain critical monitoring; if the state of charge continues to drop to the second threshold or the voltage of any single cell falls below the lower limit, the control logic drives the second-level circuit breaker to open within the same time scale, completely isolating the energy storage unit to prevent irreversible damage.

[0108] After the main power supply is restored, the control logic performs a steady-state and dynamic quality assessment of the input voltage. Once it is confirmed to meet the requirements, it first shuts down the backup power supply output stage. When the terminal voltage drops below a certain margin below the main power supply, the single-phase device is restored and cuts off, and the load returns to the main power supply without disturbance. During the entire switchback period, the high-voltage interlock logic monitors the status of all high-voltage connections and insulation barriers in real time. Any abnormality triggers an instantaneous power outage and outputs a fault message to ensure the safety of the system and personnel.

[0109] Example 3;

[0110] See also Figures 1-4 This embodiment provides a specific embodiment of a lithium iron phosphate energy storage battery pack with a rated voltage of 1500V and a rated capacity of 10kWh. The pack is composed of 320 cells with a single capacity of 31.25Ah and a nominal voltage of 3.2V, arranged in 100 parallel and 32 series. The entire pack has dimensions of 1200mm×600mm×200mm, a mass of approximately 110kg, and an energy density of 90Wh·kg -1 The battery pack is placed in an independent sealed cavity at the rear of the DC1500V high-voltage box. The cavity protection level is IP54 and is filled with nitrogen. A 3kV pressure-resistant epoxy insulation partition is set between the cavity and the low-voltage control area. The partition thickness is 5mm. The positive and negative electrodes of the battery pack are led out through silver-plated copper busbars with a cross-sectional area of ​​120mm. 2 It is connected to the external DC / DC module through ceramic through-wall terminals. The terminal creepage distance is ≥30mm and the air gap is ≥16mm, meeting the 1500V system insulation requirements.

[0111] The DC / DC backup power module utilizes a two-phase interleaved parallel synchronous buck topology. The power stage utilizes 650V / 120A silicon carbide MOSFETs operating at a switching frequency of 200kHz. The magnetic components are planar sendust core inductors with an inductance of 22μH each. The module has an input voltage range of 1100V–1800V, a nominal output of 23V, an output current capability of 22A, and a peak power of 506W. Its efficiency is ≥96% from 20%–100% load. The module's control core is a 32-bit digital signal controller that exchanges state-of-charge (SOC), state-of-ohm (SOH), and temperature information with the battery management system in real time via a CAN 2.0B bus at 250kbps. The controller adjusts the PWM duty cycle based on the SOC value in real time, with an adjustable duty cycle range of 10%–90% and a step accuracy of 0.1%, ensuring an output voltage accuracy of ±1%.

[0112] The intelligent switching unit consists of a parallel array of six 650V / 30A silicon carbide Schottky diodes. The diodes have a reverse recovery time of 45ns, a forward voltage drop of 1.35V, and a total conduction loss of 8W or less. The array is connected in reverse parallel between the main power supply DC24V bus and the backup power supply 23V output. When the main power supply voltage is higher than 23.5V, the array is in the cut-off state, and the backup power supply is in zero-power standby mode. When the main power supply drops below 23.3V, the array turns on within 2μs, and the backup power supply seamlessly takes over the entire load current. The switching delay is ≤2ms, and the load-end voltage fluctuation is ≤0.2V.

[0113] The first circuit breaker of the hierarchical protection mechanism uses a DC1500V / 63A molded case circuit breaker equipped with a DC24V shunt trip coil F11-F27, a coil resistance of 240Ω, an operating current of 100mA, and a trip time of 18ms. The second circuit breaker has the same specifications as the first circuit breaker and is equipped with shunt trip coils F12-F28. The system software is configured so that when the battery pack SOC is ≤5%, the controller broadcasts a shutdown command to the external inverter via the CAN bus. The command format is 0x18FF01XX, the data length is 8 bytes, and after a 50ms delay, the first circuit breaker trips, disconnecting non-critical loads and retaining only the RCU monitoring power consumption of ≤10W. If the SOC continues to drop to 0% or the voltage of any cell is less than 2.5V, the controller immediately trips the second circuit breaker, disconnecting the entire battery main circuit to prevent deep discharge.

[0114] In addition to F11-F28, F29 (the third circuit breaker) is DC1500V / 80A, with a temperature trigger value of 65°C, a reset hysteresis of 15°C, and an operation time of 15ms; F30 (the fourth circuit breaker) insulation monitoring adopts the balanced bridge method, with a detection voltage of 500V. When the positive and negative busbar-to-ground resistance is less than 500kΩ, F30 will trip within 10ms; F31 (the fifth circuit breaker) is linked to the high-voltage interlock, and manual reset requires a special key to prevent accidental operation.

[0115] The system temperature monitoring network consists of 16 NTC thermistors, with one sensor placed for every four battery cells. The sensor resistance is 10kΩ±1%, with Class B accuracy, a temperature measurement range of -40°C–125°C, and a resolution of 0.1°C. When the temperature difference between adjacent sensors is greater than 15°C, the controller starts two 12V / 2.4A axial flow fans with a fan volume of 60CFM. The air duct is an S-shaped aluminum profile heat sink with an 8mm thick base, a 25mm fin height, and a 3mm fin spacing. The fan continues to operate until the temperature difference is less than 10°C.

[0116] Dual CAN bus redundancy is provided, with CAN0 for real-time data and CAN1 for event triggering. The RTC utilizes an external 32.768kHz crystal oscillator. The remote upgrade interface is compatible with Ethernet-DoIP (ISO13400-2). Upgrade packages feature segmented CRC checksums and can resume downloads from breakpoints after power failures. Upgrading a 20kB firmware at 20kB / s takes just 2 minutes.

[0117] The high-voltage interlock circuit uses a dual-channel normally closed micro switch with a rated current of 1A and a stroke of 1.5mm. It is installed on the edge of the high-voltage connector and the insulating partition. The circuit is connected in series with a 24V / 5mA detection current. A disconnection at any point generates a rising edge signal. The controller cuts off the battery output within 5ms and reports the fault code 0x18FEFE01 via the CAN bus.

[0118] The system workflow is as follows:

[0119] Step 1: After the system is powered on, the main power supply AC220V is converted to DC24V by the AC / DC module, and the bus voltage is established to 24.2V. The reverse diode array is cut off, and the backup power supply is in standby mode, consuming only ≤2W to maintain the internal control circuit;

[0120] Step 2: The controller reads BMS data via the CAN bus every 100ms. If the SOC is greater than 20% and the cell voltage is greater than 3.0V, the system is marked as normal.

[0121] Step 3: When the main power supply fails and the bus voltage drops to 23.3V, the reverse diode array conducts within 2μs, and the backup power supply outputs 23V with zero load interruption.

[0122] Step 4: During the backup power supply period, the DC / DC module dynamically adjusts the duty cycle according to the SOC to maintain output accuracy; if the SOC drops to 5%, execute step 5;

[0123] Step S4A: If F30 or F31 is activated, the system enters the lock mode, prohibiting remote closing and requiring a special key on site to reset;

[0124] Step S4B: Before switching back to the main power supply, an insulation resistance test is performed to confirm that the insulation resistance is greater than 2MΩ before switching back. The test time is ≤1s.

[0125] Step 5: The controller sends a shutdown command and drives the first circuit breaker to trip, non-critical loads are powered off, and the system enters a low-power mode;

[0126] Step 6: If the SOC drops to 0% or the cell voltage is less than 2.5V, the controller drives the second circuit breaker to trip, and the battery main circuit is completely disconnected;

[0127] Step 7: After the main power is restored, the controller delays for 8 seconds to confirm that the voltage is stable. It first turns off the backup power PWM output and waits until the terminal voltage drops below 22V. The reverse diode is naturally cut off and the load returns to the main power without disturbance. Then the battery charging process is started with a charging current of 0.2C until the SOC is ≥ 95%.

[0128] Working Principle: The system consists of an AC / DC main power supply, a DC battery pack, a DC / DC backup power supply, an intelligent switching unit, a BMS, and hierarchical protection. When the main power supply is normal, the output DC24V bus supplies power to the load, and the backup power supply is reversely isolated by a SiC Schottky diode, maintaining only standby and battery inspection. When the bus voltage drops below the threshold, the diode conducts within ≤3ms, and the backup power supply outputs 23V±1% with closed-loop PWM regulation to achieve seamless switching; during this period, the duty cycle is adjusted in real time according to the SOC to maintain high efficiency. The BMS reads the SOC, SOH, and temperature through the CAN bus cycle; when the SOC is less than 5%, it first sends a shutdown command to the inverter and triggers F11-F27 to disconnect non-critical loads; if the SOC = 0% or any cell is less than 2.5V, F12-F28 disconnects the main circuit within ≤20ms to prevent deep discharge. After the main power is restored, a delay of 5-10 seconds is maintained to confirm voltage stability before shutting down the backup power supply output stage. Once the voltage at its terminals falls below the main power supply margin, the diodes naturally cut off, allowing the load to be switched back on without disruption. The entire process is monitored by a high-voltage interlock in real time, monitoring the integrity of the connectors and 3kV insulation barriers. Any anomaly is detected, with power cutoff and fault reporting within 5ms.

[0129] While the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and alterations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A dual power supply system with a high-voltage box and a built-in battery, characterized in that: include: AC / DC main power supply module, used to convert single-phase AC220V input into DC24V output; DC battery pack, composed of lithium iron phosphate cells connected in series; A DC / DC backup power supply module, the input end of which is connected to the DC battery pack and the output end of which provides a 23V DC voltage; Intelligent switching unit, including a reverse diode group connected in parallel between the main and backup circuits, used to block the backup circuit when the main power supply is normal, and turn on the backup power supply within ≤3ms when the main power supply is interrupted; Battery management communication interface, obtains battery pack SOC, SOH and temperature data through CAN bus; Hierarchical protection agencies, including: The first circuit breaker is equipped with shunt trip coils F11-F27, which cut off non-critical loads when the SOC is less than 5%. The second circuit breaker is equipped with shunt trip coils F12-F28, which disconnect the main circuit when the single-cell voltage is less than 2.5V.

2. The dual power supply system with a high-voltage box and built-in battery according to claim 1, characterized in that: The DC battery pack has a capacity of ≥10kWh, is integrated into an independent sealed cavity in the high-voltage box, and is physically isolated from the low-voltage control area by an insulating partition with a voltage resistance of ≥3kV.

3. The dual power supply system with a high-voltage box and built-in battery according to claim 1, characterized in that: The DC / DC backup power supply module adopts a high-efficiency step-down circuit with a wide voltage input range, an output voltage of 23V and a peak power of ≥500W.

4. The dual power supply system with a high-voltage box and built-in battery according to claim 1, characterized in that: The reverse diode group adopts a silicon carbide Schottky diode array, the reverse recovery time of which is ≤50ns and the forward conduction voltage drop is ≤1.5V.

5. The dual power supply system with a high-voltage box and built-in battery according to claim 1, characterized in that: The hierarchical protection mechanism also includes: The third circuit breaker is equipped with shunt trip coils F13-F29. It cuts off the battery charging circuit when the response temperature is greater than 65°C or the temperature difference between adjacent sensors is greater than 15°C, and automatically resets when the temperature is less than 50°C. The fourth circuit breaker is equipped with shunt trip coils F14-F30. When the insulation monitoring resistance is less than 500kΩ, it disconnects the high-voltage bus and reports the fault code 0x18FEFE02 through the CAN bus. The fifth circuit breaker is equipped with shunt trip coils F15-F31. It cuts off the battery output within 5ms in response to the opening of the high-voltage interlock circuit or the displacement of the partition greater than 2mm. It needs to be manually reset after the fault is eliminated.

6. A method for controlling dual power supply of a high-voltage box with a built-in battery, implemented by using the dual power supply system of a high-voltage box with a built-in battery as claimed in any one of claims 1 to 5, characterized in that: The method comprises the following steps: Step S1: monitor the main power supply voltage in real time. When the voltage is lower than the threshold, switch to the backup power supply within ≤3ms, and control the output voltage fluctuation within 23V±5% during the switching process. Step S2, periodically reading the battery pack SOC, SOH and temperature data, and adjusting them according to the intelligent switching unit; Step S3: When the SOC is less than 5%, a shutdown command is sent to the inverter and the first circuit breaker is triggered; Step S4: When SOC=0% or the cell voltage is less than 2.5V, trigger the second circuit breaker.

7. The method for controlling dual power supply of a high-voltage box with built-in batteries according to claim 6, characterized in that: The AC / DC main power module features input overvoltage, undervoltage, and phase loss protection, with thresholds set at AC275V and AC165V, respectively, and an action time of ≤50ms. It also features output overcurrent, short-circuit, and reverse polarity protection, with an overcurrent threshold of 120% of the rated current and a recovery time of ≤500ms. It also features output voltage temperature compensation with a compensation coefficient of -3mV / °C / cell, ensuring an output accuracy of ±2% within the -40°C to +85°C range.

8. The method for controlling dual power supply of a high-voltage box with built-in batteries according to claim 6, characterized in that: The DC / DC backup power module dynamically adjusts the PWM duty cycle according to the SOC to stabilize the output voltage; The DC / DC backup power supply module also includes: Input pre-charge circuit, pre-charge current ≤ 0.05C, pre-charge time 2s-5s adjustable to prevent power-on shock; Output current sharing bus, supports parallel connection of up to 8 modules, with current sharing accuracy of ±5%; Output voltage soft-start function, with a configurable startup slope of 0.5V / ms-5V / ms, suppresses inrush current.

9. The method for controlling dual power supply of a high-voltage box with built-in batteries according to claim 6, characterized in that: The intelligent switching unit further includes: Redundant reverse diode group, connected in parallel with the main diode group, automatically switches when a single group fails, with a switching time of ≤100ns; The diode temperature monitoring circuit triggers derating output and reports a fault when the junction temperature is greater than 125°C; The switching status indicator uses a dual-color LED, green for the main supply and red for the backup supply, which flashes synchronously when switching at a frequency of 1Hz.

10. The method for controlling dual power supply of a high-voltage box with built-in batteries according to claim 6, characterized in that: The battery management communication interface also includes: Redundant CAN bus, baud rate adjustable from 125kbps to 1Mbps, supports J1939 protocol; Remote upgrade interface, compatible with ISO15765-2 diagnostic specification, upgrade time <5min, power-off resume; Independent pressure relief channel, bursting pressure ≤ 50kPa and channel area ≥ 2000mm 2 ; Double-layer shielding structure, inner layer 0.8mm galvanized steel and outer layer 1.5mm aluminum alloy.

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