High-safety energy storage system and fault detection method thereof

Abstract

The invention relates to the technical field of power distribution system protection, in particular to a high-safety energy storage system and a fault detection method thereof, the system comprises a measurement and control center, an insulation monitoring device, a bidirectional DC-DC converter and an integrated DC power distribution unit, the insulation monitoring device is connected with a DC power distribution bus, and the ground insulation state of the bus is monitored in real time; the input end of the bidirectional DC-DC converter is connected with the storage battery pack, and the output end is connected with the DC power distribution bus through the integrated DC power distribution unit to construct an electric energy distribution path. The integrated direct current power distribution unit comprises a circuit breaker, two voltage detection modules and two current detection modules, the first voltage detection module is connected with the direct current power distribution bus and the measurement and control center, the second voltage detection module is connected with the circuit breaker and the measurement and control center, and the circuit breaker is connected with the direct current power distribution bus. And the two current detection modules are connected in series between the output end of the bidirectional DC-DC converter and the circuit breaker to form a current detection loop. According to the invention, through multi-level real-time monitoring and centralized control, the safety and fault response capability of the system are significantly improved.

Description

Technical Field

[0001] This invention relates to the field of power distribution system protection technology, and in particular to a high-safety energy storage system and its fault detection method. Background Technology

[0002] If faults in a substation's DC energy storage system are not diagnosed quickly, isolated accurately, and effectively handled, they will directly cause DC bus de-voltage, leading to power outages and shutdowns of the secondary system. This, in turn, will cause a chain reaction of risks, such as delayed grid fault clearing and interruption of operational status monitoring. In severe cases, it may expand the scope of the accident and threaten the overall reliability of the power grid. Statistical analysis of accidents shows that the core fault sources of substation DC energy storage systems are concentrated in the battery banks. Specifically, this manifests as: the actual capacity of the battery bank decaying below the nominal capacity during charge and discharge cycles, resulting in insufficient energy storage capacity; open-circuit faults in individual battery cells, causing power outages for the entire battery bank; and internal short-circuit faults in individual battery cells or modules under long-term float charging operation, leading to localized overheating and even fire risks.

[0003] Currently, fault isolation and protection schemes for DC energy storage systems mainly fall into two categories: The first is hard protection based on DC circuit breakers and fuses: These are connected in series in the energy storage circuit to achieve physical isolation during short-circuit faults. The DC circuit breaker relies on a mechanical arc-extinguishing mechanism to cut off the fault current, but this process is prone to generating operational overvoltages and current surges. The fuse, on the other hand, uses quartz sand filler to force-cool the arc and interrupt the fault current. Its breaking efficiency is constrained by multiple factors, including the design of the fuse core (including structure and welding process) and the parameters of the quartz sand (purity, particle size distribution, melting point, and curing process), making consistency and stability difficult to guarantee. The second is alarm protection based on the battery management system (BMS): The BMS collects parameters such as individual battery cell voltage, temperature, and charging / discharging current in real time to monitor and alarm for fault conditions. This scheme can promptly report fault information, but it only has an alarm function and lacks the ability to actively disconnect the fault circuit, thus failing to prevent the fault from spreading.

[0004] However, the above technical solutions still have the following drawbacks: Firstly, the protection functions are incomplete: DC circuit breakers and fuses are only for short-circuit faults and cannot cover non-short-circuit faults such as battery capacity decay and single-cell open circuits; BMS can only issue alarms and has no fault clearing capability, and both have protection blind spots.

[0005] Secondly, the protection reliability is insufficient: DC circuit breakers are prone to overvoltage and current surges during arc extinguishing, posing a risk of secondary faults; the breaking performance of fuses is affected by multiple parameters, resulting in poor consistency, and they are disposable devices that require manual replacement after a fault, making it impossible to quickly restore power supply.

[0006] Third, fault handling is not timely: Both types of solutions lack the "monitoring-diagnosis-handling" closed-loop capability. The BMS has no actuator, and the response speed of the circuit breaker / fuse depends on mechanical action, which cannot meet the requirements of the DC system for rapid fault handling (especially short-circuit faults require μs-ms level response). Summary of the Invention

[0007] Therefore, the technical problem to be solved by the present invention is to overcome the problems of incomplete function (such as inability to cover non-short circuit faults, alarm only without fault clearing capability), insufficient reliability (such as the arc extinguishing of circuit breakers is prone to secondary risks, and the breaking efficiency of fuses is constrained by multiple factors) and untimely fault handling in the existing DC energy storage system of substations.

[0008] To address the aforementioned technical problems, this invention provides a high-safety energy storage system and its fault detection method. The system includes: a monitoring and control center, an insulation monitoring device, a bidirectional DC-DC converter, and an integrated DC power distribution unit. The insulation monitoring device is connected to the DC power distribution bus and is used to monitor the bus's insulation status to ground in real time. The input terminal of the bidirectional DC-DC converter is connected to a battery pack, and its output terminal is connected to the DC power distribution bus via the integrated DC power distribution unit, thus establishing a power distribution path. The integrated DC power distribution unit includes: a circuit breaker, a first voltage detection module, a second voltage detection module, a first current detection module, and a second current detection module; The first voltage detection module is connected between the DC power distribution bus and the measurement and control center; the second voltage detection module is connected between the circuit breaker and the measurement and control center, and the circuit breaker is connected to the DC power distribution bus. The first current detection module and the second current detection module are connected in series on the connection branch between the output terminal of the bidirectional DC-DC converter and the circuit breaker to form a current detection loop.

[0009] In one embodiment of the present invention, the bidirectional DC-DC converter includes an input unit, a power conversion unit, and an output unit; wherein, The input unit includes a first capacitor, with a first end connected to the positive terminal of the battery pack and a second end connected to the negative terminal of the battery pack. The power conversion unit includes a first inductor, a second inductor, a first power switch, a second power switch, a third power switch, and a fourth power switch. A first end of the first inductor is connected to the positive terminal of the battery pack, and a second end of the first inductor is connected to the emitter of the first power switch and the collector of the second power switch. The emitter of the second power switch is connected to the negative terminal of the battery pack. Similarly, a first end of the second inductor is connected to the positive terminal of the battery pack, and a second end of the second inductor is connected to the emitter of the third power switch and the collector of the fourth power switch. The emitter of the fourth power switch is connected to the emitter of the second power switch. The output unit includes a second capacitor, the first end of which is connected to the collectors of the first power switch and the second power switch, and the second end of which is connected to the emitter of the fourth power switch.

[0010] In one embodiment of the present invention, the first end of the second capacitor is connected to the positive terminal of the DC distribution bus via the circuit breaker, and the second end is connected to the negative terminal of the DC distribution bus, forming a low ripple filter circuit on the output side.

[0011] In one embodiment of the present invention, the bidirectional DC-DC converter further includes a control unit, the control unit including a first current transformer, a second current transformer, a first sampling resistor, a second sampling resistor, and a control chip; Wherein, one end of the first current transformer is connected to the output terminal of the battery pack, and the other end is connected to the first current sampling pin of the control chip and the first sampling resistor, and the other end of the first sampling resistor is grounded; one end of the second current transformer is connected to the DC power distribution bus, and the other end is connected to the second current sampling pin of the control chip and the second sampling resistor, and the other end of the second sampling resistor is grounded.

[0012] In one embodiment of the present invention, the control unit further includes a third sampling resistor and a fourth sampling resistor, the common connection point of the third sampling resistor and the fourth sampling resistor is connected to the voltage sampling pin of the control chip, the other end of the third sampling resistor is connected to the DC power distribution bus, and the other end of the fourth sampling resistor is grounded.

[0013] In one embodiment of the present invention, the PWM signal output pin of the control chip is connected to the control terminals of the first power switch, the second power switch, the third power switch and the fourth power switch.

[0014] In one embodiment of the present invention, both the first current detection module and the second current detection module are connected to the measurement and control center. The first current detection module is used to collect current data when the system is faulty, and the second current detection module is used to collect current data when the system is operating normally.

[0015] In one embodiment of the present invention, the monitoring and control center controls the connection of the circuit breaker.

[0016] In one embodiment of the present invention, the system further includes a first fuse, a second fuse and a third fuse, the first voltage detection module is connected to the DC distribution bus via the first fuse, the second voltage detection module is connected to the circuit breaker via the second fuse, and the bidirectional DC-DC converter is connected to the battery pack via the third fuse.

[0017] On the other hand, the present invention also provides a fault detection method for the above-mentioned system, the fault detection method comprising the following steps: S1: After the system is powered on, it performs hardware self-test on the insulation monitoring device, the integrated DC power distribution unit, and the bidirectional DC-DC converter, and sets the detection parameters, including the normal operating voltage threshold of the DC power distribution bus, the insulation fault judgment threshold, the short circuit fault judgment threshold, and the battery pack charging and discharging voltage threshold. After initialization, it enters the cyclic monitoring mode. S2: The insulation monitoring device collects the ground insulation status data of the DC distribution bus in real time, and determines whether an insulation fault has been triggered based on the ground insulation status data. If so, the monitoring and control center will immediately activate the audible and visual alarms, upload the fault information, and initiate the manual troubleshooting and repair process; If not, proceed to step S3 to perform multi-type fault detection; S3: The integrated DC power distribution unit collects current and voltage signals of the DC power distribution bus under different states to determine whether a non-short-circuit fault is triggered. If so, the bidirectional DC-DC converter automatically executes the corresponding protection action according to the fault type, and the measurement and control center records the fault type, fault occurrence time and current / voltage waveform. After the fault is handled, it returns to step S2 to monitor again. If not, proceed to step S4 to perform short-circuit fault detection; S4: Determine if a short circuit fault has been triggered. If so, the bidirectional DC-DC converter is first triggered to lock out its internal power switch and cut off the power circuit; if the bidirectional DC-DC converter fails to lock out, the backup protection of the integrated DC power distribution unit is triggered, which cuts off the fault circuit. After the fault occurs, the monitoring and control center starts the audible and visual alarm and uploads the fault information, and enters the manual troubleshooting and repair process. If not, proceed to step S5 and perform normal operation adjustment; S5: The measurement and control center controls the operating mode of the bidirectional DC-DC converter based on the DC bus voltage signal collected by the integrated DC power distribution unit and the battery pack voltage signal collected by the bidirectional DC-DC converter, combined with the preset normal operating voltage threshold of the DC power distribution bus and the charging and discharging voltage threshold of the battery. When the DC bus voltage rises to the upper limit of normal operating voltage due to photovoltaic power input or back electromotive force, the bidirectional DC-DC converter is controlled to enter buck mode to charge the battery pack with constant current until the DC bus voltage drops to the normal range, and the converter returns to standby mode. When the DC bus voltage drops to the lower limit of normal operating voltage due to insufficient power supply or increased load, and the battery pack voltage meets the discharge conditions, the bidirectional DC-DC converter is controlled to enter boost mode. The battery pack discharges to the DC bus at a constant current through the converter until the DC bus voltage rises to the normal range. If the battery pack voltage is lower than the discharge cutoff voltage, the boost mode discharge stops, and the converter returns to standby mode. After completing one normal adjustment, it returns to step S2 to re-enter the cycle monitoring.

[0018] The technical solution of the present invention has the following advantages compared with the prior art: Firstly, the insulation monitoring device monitors the insulation status of the busbar to ground in real time. The integrated DC power distribution unit is equipped with a dual voltage detection module (to accurately monitor the voltage on the busbar and circuit breaker side) and a dual current detection module (to collect fault current and normal small current respectively). Combined with the current and voltage sampling functions of the bidirectional DC-DC converter, it can achieve accurate data collection under all operating conditions, providing a reliable basis for fault diagnosis and system control.

[0019] Secondly, the bidirectional DC-DC converter adopts a two-phase interleaved parallel Buck-Boost topology, and is equipped with input and output filter capacitors to build a low ripple circuit. It can not only flexibly switch the working mode through the output PWM signal of the control chip to stabilize the bus voltage and realize the efficient charging and discharging of the battery, but also quickly lock the power switch in the event of a short circuit fault, forming a first-level protection at the μs level.

[0020] Third, the integrated DC power distribution unit serves as backup protection. It can disconnect fault circuits in milliseconds through circuit breakers, forming dual short-circuit protection with the converter. It also has the ability to protect against multiple types of faults. Furthermore, the monitoring and control center can directly control the circuit breaker and the connected converter control unit to achieve rapid fault response and coordinated system management. This effectively solves the problems of incomplete protection, slow response, and low reliability of existing solutions, and comprehensively improves the safety, stability, and operating efficiency of the substation DC energy storage system. Attached Figure Description

[0021] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein... Figure 1 This is a schematic diagram of a high-security energy storage system provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of a high-security energy storage system provided in an embodiment of the present invention; Figure 3 This is the circuit topology diagram of a bidirectional DC-DC converter; Figure 4 This is a schematic diagram of the control unit of the bidirectional DC-DC converter; Figure 5 This is a schematic flowchart of a fault detection method for a high-safety energy storage system provided in an embodiment of the present invention; Explanation of reference numerals in the accompanying drawings: 1. Measurement and control center; 2. Insulation monitoring device; 3. Bidirectional DC-DC converter; 31. Input unit; 32. Power conversion unit; 33. Output unit; 34. Control unit; 4. Integrated DC power distribution unit; 41. Circuit breaker; 100. DC power distribution bus; 200. Battery pack. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0023] Example 1: like Figure 1 and Figure 2 As shown, the present invention provides a high-safety energy storage system, specifically including: a monitoring and control center 1, an insulation monitoring device 2, a bidirectional DC-DC converter 3, and an integrated DC power distribution unit 4; wherein, the insulation monitoring device 2 is connected to the DC power distribution bus 100 and is used to monitor the insulation status of the bus to ground in real time; the input end of the bidirectional DC-DC converter 3 is connected to the battery pack 200, and its output end is connected to the DC power distribution bus 100 via the integrated DC power distribution unit 4 to form an energy distribution path; The integrated DC power distribution unit 4 includes: a circuit breaker 41, a first voltage detection module PT1, a second voltage detection module PT2, a first current detection module TA1, and a second current detection module TA2; The first voltage detection module PT1 is connected between the DC power distribution bus 100 and the measurement and control center 1; the second voltage detection module PT2 is connected between the circuit breaker 41 and the measurement and control center 1, and the circuit breaker 41 is connected to the DC power distribution bus 100. The first current detection module TA1 and the second current detection module TA2 are connected in series on the connection branch between the output terminal of the bidirectional DC-DC converter 3 and the circuit breaker 41 to form a current detection loop.

[0024] As can be seen from the above technical solution, the present invention captures the insulation status of the DC distribution bus 100 to ground in real time through the insulation monitoring device 2, which can promptly detect insulation degradation or grounding hazards; the integrated DC distribution unit 4 is equipped with dual voltage detection modules and dual current detection modules, and combined with the full-link data acquisition of "bus-circuit breaker-converter", it can accurately acquire voltage and current information under different operating conditions, and provide complete data support for fault diagnosis and system control.

[0025] Secondly, the bidirectional DC-DC converter 3 and the integrated DC power distribution unit 4 form dual fault protection: in the event of a short circuit fault, the converter can take priority to achieve rapid fault isolation, and the integrated DC power distribution unit 4, as a backup protection, can cut off the circuit in time when the converter fails to prevent the fault from spreading; at the same time, insulation monitoring and voltage and current detection work together to cover multiple risks such as insulation faults and short circuit faults, solving the problem of single function of traditional protection.

[0026] Furthermore, the bidirectional DC-DC converter 3 connects the battery pack 200 and the DC power distribution bus 100 to establish a stable power distribution path. In conjunction with the overall control of each module by the monitoring and control center 1 (such as the on / off control of the circuit breaker 41 and the regulation of the converter's operating status), it can not only ensure the flexible bidirectional transmission of energy between the battery and the bus, but also ensure the safety and stability of the power distribution process through full-link monitoring and protection logic, thus meeting the high reliability requirements of the substation DC energy storage system.

[0027] Furthermore, both the first current detection module TA1 and the second current detection module TA2 are connected to the measurement and control center 1. The first current detection module TA1 is used to collect current data when the system is faulty, and the second current detection module TA2 is used to collect current data when the system is operating normally. The measurement and control center 1 controls the circuit breaker 41.

[0028] Preferably, the system further includes a first fuse FU1, a second fuse FU2, and a third fuse FU3. The first voltage detection module PT1 is connected to the DC distribution bus 100 via the first fuse FU1, and the second voltage detection module PT2 is connected to the circuit breaker 41 via the second fuse FU2. These modules are specifically designed to monitor the voltage of the energy storage branch when the energy storage system is in operation after the circuit breaker 41 is closed, to verify the voltage stability of the system under operating conditions. The bidirectional DC-DC converter 3 is connected to the battery pack 200 via the third fuse FU3.

[0029] like Figure 3 As shown, the bidirectional DC-DC converter 3 includes an input unit 31, a power conversion unit 32, and an output unit 33; wherein, The battery pack 200 provides electrical energy to the system or absorbs electrical energy (bidirectional flow), and is the source of energy input / output. Its voltage is denoted as... ; The input unit 31 includes a first capacitor C1. The first end of the first capacitor C1 is connected to the positive terminal of the battery pack 200, and its second end is connected to the negative terminal of the battery pack 200. It is used to filter out the side voltage ripple of the battery pack 200, stabilize the input voltage, reduce the voltage impact on the battery due to the operation of the converter, and suppress the current harmonics injected by the battery into the converter. The power conversion unit 32 includes a first inductor L1, a second inductor L2, a first power switch S1, a second power switch S2, a third power switch S3, and a fourth power switch S4. The first end of the first inductor L1 is connected to the positive terminal of the battery pack 200, and its second end is connected to the emitter of the first power switch S1 and the collector of the second power switch S2. The emitter of the second power switch S2 is connected to the negative terminal of the battery pack 200. The first end of the second inductor L2 is connected to the positive terminal of the battery pack 200, and its second end is connected to the emitter of the third power switch S3 and the collector of the fourth power switch S4. The emitter of the fourth power switch S4 is connected to the emitter of the second power switch S2. The first inductor L1 and the second inductor L2 are two sets of energy storage inductors with interleaved parallel branches. The two inductors usually have the same value. Interleaving control is used to reduce current ripple and realize energy storage and transfer. In Buck mode (step-down charging), the inductors store electrical energy and release it to the battery pack 200 side; in Boost mode (step-up discharging), the inductors store electrical energy and release it to the DC distribution bus 100 side.

[0030] The first power switch S1, the second power switch S2, the third power switch S3, and the fourth power switch S4 are all N-channel IGBTs. The first power switch S1 and the second power switch S2 form one group, and the third power switch S3 and the fourth power switch S4 form another group. The drive signals of the two groups of switches are 180° out of phase. Each switch has an internal anti-parallel body diode to provide a current path during the freewheeling phase.

[0031] The output unit 33 includes a second capacitor C2. The first end of the second capacitor C2 is connected to the collectors of the first power switch S1 and the second power switch S2, and its second end is connected to the emitter of the fourth power switch S4.

[0032] Specifically, the first terminal of the second capacitor C2 is connected to the positive terminal of the DC distribution bus 100 via the circuit breaker 41, and its second terminal is connected to the negative terminal of the DC distribution bus 100, forming a low-ripple filter circuit on the output side to stabilize the DC bus voltage. It provides a smooth voltage for the bus-side load / battery.

[0033] Furthermore, such as Figure 4 As shown, the bidirectional DC-DC converter 3 also includes a control unit 34, which includes a first current transformer CT0, a second current transformer CT1, a first sampling resistor R1, a second sampling resistor R2, and a control chip U1. Wherein, one end of the first current transformer CT0 is connected to the output terminal of the battery pack 200, and the other end is connected to the first current sampling pin AN0 of the control chip U1 and the first sampling resistor R1, and the other end of the first sampling resistor R1 is grounded; one end of the second current transformer CT1 is connected to the DC power distribution bus 100, and the other end is connected to the second current sampling pin AN2 of the control chip U1 and the second sampling resistor R2, and the other end of the second sampling resistor R2 is grounded.

[0034] The control unit 34 also includes a third sampling resistor R3 and a fourth sampling resistor R4. The common connection point of the third sampling resistor R3 and the fourth sampling resistor R4 is connected to the voltage sampling pin AN1 of the control chip U1. The other end of the third sampling resistor R3 is connected to the DC power distribution bus 100, and the other end of the fourth sampling resistor R4 is grounded.

[0035] The PWM signal output pins (PWM1, PWM2, PWM3, PWM4) of the control chip U1 respectively control the bases of the first power switch S1, the second power switch S2, the third power switch S3, and the fourth power switch S4, thereby realizing the fault-breaking function of the solid-state circuit breaker. The first power switch S1, the second power switch S2, the third power switch S3, and the fourth power switch S4 are divided into two groups, and the control chip U1 controls the phase difference of the drive signals of the two groups of switches to be 180°.

[0036] In Buck mode, the bidirectional DC-DC converter 3 charges the battery pack 200 from the DC distribution bus 100. Its operation is as follows: The PWM signal output by control chip U1 keeps the second power switch S2 and the fourth power switch S4 off, while the first power switch S1 and the third power switch S3 operate alternately in an interleaved manner (i.e., when the first power switch S1 is on, the third power switch S3 is off, and when the third power switch S3 is on, the first power switch S1 is off, to avoid current fluctuations). When the first power switch S1 is on, the DC bus voltage U... bus The power supply will pass through the circuit breaker 41, the second capacitor C2 of the output unit 32, and the first power switch S1, which is in operation, to the first inductor L1; when the third power switch S3 is turned on, U bus Then, through the same pre-stage path, the power is supplied to the second inductor L2 via the conducting third power switch S3. During this process, the first inductor L1 and the second inductor L2 will store energy respectively, and the inductor current will gradually increase.

[0037] When the first power switch S1 or the third power switch S3 is turned off, the first inductor L1 will release energy through the freewheeling diode D2 connected in anti-parallel inside the second power switch S2, and the second inductor L2 will release energy through the freewheeling diode D4 connected in anti-parallel inside the fourth power switch S4. At this time, the current released by the inductor will form a complete circuit through the battery pack 200, thereby realizing stable charging of the battery.

[0038] During the above process, the control unit 34 collects the bus side current through the second current transformer CT1 and the bus voltage through the voltage divider resistors (third sampling resistor R3 and fourth sampling resistor R4), and adjusts the PWM duty cycle in real time to achieve stable step-down charging.

[0039] In Boost mode, the bidirectional DC-DC converter 3 transfers energy from the battery pack 200 to the DC distribution bus 100, i.e., the battery discharges to supply power to the bus. Its operation is as follows: The PWM signal output by the control chip U1 keeps the first power switch S1 and the third power switch S3 off, while the second power switch S2 and the fourth power switch S4 are turned on and off alternately.

[0040] When the second power switch S2 is turned on, the battery pack 200 will directly supply power to the first inductor L1; when the fourth power switch S4 is turned on, the battery pack 200 will directly supply power to the second inductor L2. At this time, current will flow through the corresponding inductors, so that the first inductor L1 and the second inductor L2 store energy respectively, and the inductor current gradually increases.

[0041] When the second power switch S2 or the fourth power switch S4 is turned off, the first inductor L1 releases energy through the freewheeling diode D1 connected in anti-parallel inside the first power switch S1, and the second inductor L2 releases energy through the freewheeling diode D3 connected in anti-parallel inside the third power switch S3. The energy released by the inductors is superimposed with the output voltage of the battery pack 200 to form a higher voltage, which then supplies power to the DC distribution bus 100, ultimately realizing the voltage boosting function and completing the energy transfer from the battery to the bus.

[0042] Example 2: Based on the same inventive concept, the present invention also provides a fault detection method applied to the system described in Embodiment 1, such as... Figure 5 As shown, the fault detection method includes the following steps: S1: After the system is powered on, an initialization operation is performed: the insulation monitoring device 2, the bidirectional DC-DC converter 3, and the integrated DC power distribution unit 4 are subjected to hardware self-tests, and the detection parameters are set, including the normal operating voltage threshold of the DC power distribution bus 100, the insulation fault judgment threshold, the short circuit fault judgment threshold, and the charging and discharging voltage threshold of the battery pack 200. After the initialization is completed, the system enters the cyclic monitoring mode. S2: The insulation monitoring device 2 collects the ground insulation status data of the DC distribution bus 100 in real time to avoid secondary accidents caused by grounding faults. Based on the ground insulation status data, it determines whether an insulation fault has been triggered. If so, the monitoring and control center 1 will immediately activate the audible and visual alarm, upload the fault information, and initiate the manual troubleshooting and repair process; If not, proceed to step S3 to perform multi-type fault detection; S3: The integrated DC power distribution unit 4 collects the current and voltage signals of the DC power distribution bus 100 under different states to determine whether a non-short-circuit fault is triggered. If so, the bidirectional DC-DC converter 3 and the integrated DC distribution unit 4 automatically execute corresponding protection actions according to the fault type. The monitoring and control center 1 records the fault type, fault occurrence time, and current / voltage waveforms, and returns to step S2 for re-monitoring after the fault is handled. Specifically, the bidirectional DC-DC converter 3 and the integrated DC distribution unit 4 trigger corresponding protection actions according to the fault type, including: For current increment faults, if the current increment is greater than or equal to the first-stage threshold (1 times the rated current), the integrated DC power distribution unit 4 immediately initiates forward / reverse direction discrimination, triggers the first-stage current increment protection in the corresponding direction, and drives the circuit breaker 41 to trip without delay; if the current increment is greater than or equal to the second-stage threshold (0.5 times the rated current) and less than the first-stage threshold, a 200ms delay is initiated. If the increment continues to exceed the limit within the delay, the second-stage protection trips; at the same time, the control chip U1 of the bidirectional DC-DC converter 3 receives the fault signal and blocks the PWM output (assisting in cutting off the power circuit). For voltage-related faults, if U bus If the overvoltage threshold is exceeded, the integrated DC power distribution unit 4 triggers overvoltage protection. It first sends a "blocked boost mode" command to the bidirectional DC-DC converter 3. If U... bus If the voltage does not drop below 110% of the rated voltage, the circuit breaker 41 will trip; if U bus If the voltage is below the low voltage threshold, low voltage protection is triggered, and the bidirectional DC-DC converter 3 enters boost mode (battery discharge voltage compensation). If U... bus If U does not return to the normal range, disconnect unnecessary loads; bus When the current is within the normal range (>60% of the rated voltage) and the current is ≥ the overcurrent threshold, the low-voltage blocking overcurrent protection is triggered (first stage overcurrent 1.5 times the rated current, second stage overcurrent 1.2 times the rated current). When the voltage is <60% of the rated voltage, the overcurrent protection is blocked. For grounding faults, if the leakage current uploaded by the insulation monitoring device 2 is ≥50mA, the integrated DC power distribution unit 4 triggers the grounding leakage current protection, combined with the U collected by PT1. bus Determine the grounding polarity (U when the positive terminal is grounded) bus When the negative terminal voltage to ground increases (and when the negative terminal is grounded, the positive terminal voltage to ground increases), the circuit breaker 41 is tripped to prevent the ground fault from escalating into a short circuit. For reverse power faults, if the power P calculated by the bidirectional DC-DC converter 3 is less than 0 (reverse power) and the amplitude is greater than or equal to 5% of the rated power, after 50ms, the integrated DC power distribution unit 4 triggers reverse power protection, cuts off the circuit breaker 41, and prevents the load from feeding back power to the battery pack 200. For overload faults: if the current continues to exceed the rated value and meets the inverse time characteristic (e.g., 1.2 times the rated current for 10 minutes), the integrated DC power distribution unit 4 will trigger the overload thermal protection. If there is no manual intervention, it will trip according to the time limit. If not, proceed to step S4 to perform short-circuit fault detection; S4: Determine if a short circuit fault has been triggered. If so, the control chip U1 of the bidirectional DC-DC converter 3 quickly blocks the first to fourth power switches and disconnects the power circuit between the battery pack 200 and the DC distribution bus 100 through the PWM signal to prevent the fault current from continuing to increase; if the control chip U1 fails to block, the backup protection of the integrated DC distribution unit 4 is triggered, and the instantaneous overcurrent protection is immediately started (after the forward / reverse direction is determined, the circuit breaker 41 trips within 5ms), which disconnects the fault circuit. After the fault occurs, the measurement and control center 1 starts the audible and visual alarm and uploads the fault information, and enters the manual troubleshooting and repair process; If not, proceed to step S5 and perform normal operation adjustment; S5: The measurement and control center 1 controls the operating mode of the bidirectional DC-DC converter 3 based on the DC bus voltage signal collected by the integrated DC power distribution unit 4 and the battery pack voltage signal collected by the bidirectional DC-DC converter 3, combined with the preset normal operating voltage threshold of the DC power distribution bus 100 and the battery charging and discharging voltage threshold. When the DC bus voltage rises to the upper limit of normal operating voltage due to photovoltaic power input or back electromotive force, the bidirectional DC-DC converter 3 is controlled to enter buck mode to charge the battery pack 200 with constant current until the DC bus voltage drops to the normal range, and the converter returns to standby state. When the DC bus voltage drops to the lower limit of normal operating voltage due to insufficient power supply or increased load, and the voltage of battery pack 200 meets the discharge conditions, the bidirectional DC-DC converter 3 is controlled to enter boost mode. Battery pack 200 discharges to the DC bus at a constant current through the converter until the DC bus voltage rises to the normal range. If the voltage of battery pack 200 is lower than the discharge cutoff voltage, the boost mode discharge stops, and the converter returns to standby mode. After completing one normal adjustment, it returns to step S2 to re-enter the cycle monitoring, forming a continuous cycle of "monitoring-adjustment-re-monitoring" to ensure long-term stable operation of the system.

[0043] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A high safety energy storage system, characterized by, The application relates to a DC power distribution unit, which comprises the following components: a control center; an insulation monitoring device connected to a DC power distribution bus for monitoring the insulation state of the bus in real time; a bidirectional DC-DC converter, the input end of which is connected to a battery pack; and an integrated DC power distribution unit, the output end of the bidirectional DC-DC converter being connected to the DC power distribution bus via the integrated DC power distribution unit to form a power distribution channel. The integrated DC power distribution unit comprises a circuit breaker, a first voltage detection module, a second voltage detection module, a first current detection module and a second current detection module. The first voltage detection module is connected between the DC power distribution bus and the control center; the second voltage detection module is connected between the circuit breaker and the control center, and the circuit breaker is connected to the DC power distribution bus. The first current detection module and the second current detection module are arranged in series on a connecting branch between the output end of the bidirectional DC-DC converter and the circuit breaker to form a current detection loop. The bidirectional DC-DC converter comprises an input unit, a power conversion unit and an output unit. The input unit comprises a first capacitor, the first end of which is connected to the positive pole of the battery pack, and the second end of which is connected to the negative pole of the battery pack. The power conversion unit comprises a first inductor, a second inductor, a first power switch tube, a second power switch tube, a third power switch tube and a fourth power switch tube. The output unit comprises a second capacitor, the first end of which is connected to the collector of the first power switch tube and the second power switch tube, and the second end of which is connected to the emitter of the fourth power switch tube.

2. The high safety energy storage system of claim 1, wherein, The first end of the second capacitor is connected to the positive pole of the DC power distribution bus via the circuit breaker, and the second end of the second capacitor is connected to the negative pole of the DC power distribution bus to form an output side low-ripple filter loop. The bidirectional DC-DC converter further comprises a control unit, which comprises a first current transformer, a second current transformer, a first sampling resistor, a second sampling resistor and a control chip. One end of the first current transformer is connected to the output end of the battery pack, and the other end is connected to the first current sampling pin of the control chip and the first sampling resistor, and the other end of the first sampling resistor is grounded. One end of the second current transformer is connected to the DC power distribution bus, and the other end is connected to the second current sampling pin of the control chip and the second sampling resistor, and the other end of the second sampling resistor is grounded.

3. The high safety energy storage system of claim 2, wherein, ​ 4. The high safety energy storage system of claim 2, wherein, ​ ​ 5. The high safety energy storage system of claim 4, wherein, The control unit further comprises a third sampling resistor and a fourth sampling resistor, a common connection point of the third sampling resistor and the fourth sampling resistor is connected to a voltage sampling pin of the control chip, the other end of the third sampling resistor is connected to the DC power distribution bus, and the other end of the fourth sampling resistor is grounded.

6. The high safety energy storage system of claim 4, wherein, The PWM signal output pin of the control chip is connected to the control end of the first power switch tube, the second power switch tube, the third power switch tube and the fourth power switch tube.

7. The high-safety energy storage system of claim 1, wherein, The first current detection module and the second current detection module are connected to the measurement and control center, the first current detection module is used for collecting current data when the system fails, and the second current detection module is used for collecting current data when the system normally operates.

8. The high-safety energy storage system of claim 1, wherein, The measurement and control center is connected to the circuit breaker.

9. The high-safety energy storage system of claim 1, wherein, The system further comprises a first fuse, a second fuse and a third fuse, the first voltage detection module is connected to the DC power distribution bus via the first fuse, the second voltage detection module is connected to the circuit breaker via the second fuse, and the bidirectional DC-DC converter is connected to the battery pack via the third fuse.

10. A fault detection method applied to the system according to any one of claims 1 to 9, characterized in that, The steps include: S1: After the system is powered on, the insulation monitoring device, the integrated DC power distribution unit and the bidirectional DC-DC converter are subjected to hardware self-checking, and detection parameters are set, including a DC power distribution bus normal working voltage threshold, an insulation fault determination threshold, a short circuit fault determination threshold and a battery pack charging and discharging voltage threshold, and after initialization is completed, a circulating monitoring mode is entered; S2: The insulation monitoring device collects real-time ground insulation state data of the DC power distribution bus, and determines whether an insulation fault is triggered according to the ground insulation state data: If yes, the measurement and control center immediately starts an audible and visual alarm, uploads fault information and enters a manual troubleshooting and repair process; If no, step S3 is entered, and multiple types of fault detection are performed; S3: The integrated DC power distribution unit collects current signals and voltage signals of the DC power distribution bus in different states, and determines whether a non-short-circuit fault is triggered: If yes, the bidirectional DC-DC converter automatically performs corresponding protection actions according to the fault type, the measurement and control center records the fault type, the fault occurrence time and the current / voltage waveform, and returns to step S2 for re-monitoring after the fault is handled; If no, step S4 is entered, and short circuit fault detection is performed; S4: Determine whether a short circuit fault is triggered: If yes, the bidirectional DC-DC converter preferentially locks its internal power switch tube and cuts off the power circuit; if the bidirectional DC-DC converter fails to lock, the backup protection of the integrated DC power distribution unit is triggered to cut off the fault circuit, and after the fault occurs, the measurement and control center starts an audible and visual alarm and uploads fault information, and enters a manual troubleshooting and repair process; If no, step S5 is entered, and normal operation adjustment is performed; S5: the measurement and control center controls the working mode of the bidirectional DC-DC converter according to the DC bus voltage signal collected by the integrated DC power distribution unit and the storage battery voltage signal collected by the bidirectional DC-DC converter, in combination with the preset normal working voltage threshold of the DC power distribution bus and the preset charging and discharging voltage threshold of the storage battery: When the DC bus voltage rises to the upper limit of the normal working voltage due to the input of the photovoltaic power supply or the back electromotive force, the bidirectional DC-DC converter is controlled to enter the step-down mode to perform constant-current charging on the storage battery group until the DC bus voltage drops to the normal range, and the converter returns to the standby state; When the DC bus voltage drops to the lower limit of the normal working voltage due to insufficient power supply or heavy load, and the voltage of the storage battery group meets the discharging condition, the bidirectional DC-DC converter is controlled to enter the step-up mode, and the storage battery group discharges to the DC bus through the converter at a constant current until the DC bus voltage rises to the normal range, if the voltage of the storage battery group is lower than the discharging cutoff voltage, the discharging in the step-up mode is stopped, and the converter returns to the standby state; after completing the normal adjustment, the step S2 is returned to re-enter the cycle monitoring.

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