A direct current micro-grid system of photovoltaic access to electrolytic aluminum

Abstract

This application discloses a photovoltaic DC microgrid system for electrolytic aluminum, belonging to the field of aluminum electrolytic cell power supply technology. The DC microgrid system provided by this application includes: a prefabricated compartment; a positive bus protection cabinet, the input terminal of which is connected to the positive DC output terminal of the prefabricated compartment, and the output terminal connected to the input terminal of a positive bus fuse cabinet, the output terminal of which is electrically connected to the aluminum electrolytic DC positive bus; a negative bus protection cabinet, the input terminal of which is connected to the negative DC output terminal of the prefabricated compartment, and the output terminal connected to the input terminal of a negative bus fuse cabinet, the output terminal of which is electrically connected to the aluminum electrolytic DC negative bus; post insulators; the aluminum electrolytic DC positive bus and the aluminum electrolytic DC negative bus connect to multiple aluminum electrolytic cells. This achieves safe access of photovoltaic DC power in the aluminum electrolysis environment.

Description

Technical Field

[0001] This application belongs to the field of power supply technology for aluminum electrolytic cells, and particularly relates to a DC microgrid system for photovoltaic access in aluminum electrolysis. Background Technology

[0002] Electrolytic aluminum production utilizes a high-voltage, high-current DC power supply system, while photovoltaic (PV) power generation itself outputs DC electricity. Based on a PV-electrolytic aluminum DC microgrid, PV power generation is directly connected to supply electricity to the aluminum electrolysis cells, eliminating the inverter-rectifier stage in traditional power supply models and significantly reducing power conversion losses. This technology overcomes the limitation that large-capacity PV power can only be connected to auxiliary production power systems, significantly increasing the proportion of renewable energy in the electricity consumption of electrolytic aluminum production and enhancing the local absorption capacity of PV power generation.

[0003] In the existing technology, the positive and negative busbars of photovoltaic DC adopt a double-input and double-output design arranged in the same cabinet. Power transmission is achieved through the busbar structure arranged in close proximity in the protection cabinet. The positive and negative busbars complete the input and output functions in a single cabinet and rely on the passive insulation protection mechanism of the cabinet being directly grounded to maintain system operation.

[0004] However, in the existing technology, the arrangement of the positive and negative DC busbars of photovoltaics in the same cabinet makes it easy for short circuit accidents to occur under complex operating conditions, and the insulation protection mechanism is difficult to effectively block the leakage current path. Summary of the Invention

[0005] This application discloses a DC microgrid system for photovoltaic access to electrolytic aluminum, which aims to solve the technical problems of short-circuit risk and insufficient insulation caused by the existing arrangement of photovoltaic DC positive and negative busbars in the same cabinet.

[0006] To achieve the above objectives, the technical solution of this application is: The first aspect of this application provides a DC microgrid system for photovoltaic access in electrolytic aluminum, comprising: The prefabricated compartment is used to convert the light energy collected by the photovoltaic panels into photovoltaic DC electricity, including a negative DC output terminal and a positive DC output terminal; A positive bus protection cabinet, wherein the input terminal of the positive bus protection cabinet is connected to the positive DC output terminal of the prefabricated compartment, the output terminal is connected to the input terminal of the positive bus fuse cabinet, and the output terminal of the positive bus fuse cabinet is electrically connected to the aluminum electrolysis DC positive bus. The negative busbar protection cabinet has its input terminal connected to the negative DC output terminal of the prefabricated compartment, and its output terminal connected to the input terminal of the negative busbar fuse cabinet. The output terminal of the negative busbar fuse cabinet is electrically connected to the aluminum electrolysis DC negative busbar. The post insulator is provided at the bottom of the negative busbar protection cabinet, the negative busbar fuse cabinet, the positive busbar protection cabinet, and the positive busbar fuse cabinet, respectively. The aluminum electrolysis DC positive bus and the aluminum electrolysis DC negative bus are connected to multiple aluminum electrolysis cells.

[0007] Preferably, in conjunction with the first aspect, it further includes: An insulation monitoring module is installed inside the negative busbar protection cabinet and / or the positive busbar protection cabinet to monitor the leakage current between the high-voltage busbar inside the protection cabinet and the cabinet shell in real time.

[0008] In conjunction with the first aspect, preferably, a first disconnecting switch is connected in series between the positive bus protection cabinet and the positive bus fuse cabinet; A second disconnecting switch is connected in series between the negative busbar protection cabinet and the negative busbar fuse cabinet.

[0009] In conjunction with the first aspect, preferably, the insulation monitoring module is provided with a first threshold and a second threshold; and the first threshold is less than the second threshold; When the insulation monitoring module detects that the leakage current is greater than or equal to the first threshold and less than the second threshold, it triggers an early warning signal; When the insulation monitoring module detects that the leakage current is greater than or equal to the second threshold, it triggers the first disconnect switch and the second disconnect switch to trip simultaneously.

[0010] In conjunction with the first aspect, preferably, both the positive busbar fuse cabinet and the negative busbar fuse cabinet are equipped with fuses; The fuse's melting time is configured to be less than the opening time of the first or second disconnecting switch; If an overcurrent fault occurs that exceeds the rated current of the first or second disconnecting switch, the first and second disconnecting switches will trip simultaneously. If a short-circuit current fault exceeding the breaking capacity of the first or second disconnecting switch occurs, the fuse shall blow in priority over the first or second disconnecting switch.

[0011] In conjunction with the first aspect, preferably, the positive busbar protection cabinet and the negative busbar protection cabinet are spatially independent of each other, and the distance between the two cabinets is not less than 1.5 m.

[0012] In conjunction with the first aspect, preferably, the number of post insulators at the bottom of each cabinet is at least four; The rated voltage of the post insulator shall not be less than 10 kV, and the bending failure load shall not be less than 20 kN; The height of the post insulator is 150-250 mm.

[0013] In conjunction with the first aspect, preferably, the prefabricated cabin is equipped with an energy conversion module; The prefabricated compartment is connected to the positive bus protection cabinet, the negative bus protection cabinet, the negative bus fuse cabinet, and the positive bus fuse cabinet via signal connection. When the system detects a fault that cannot be quickly eliminated, the power conversion module in the prefabricated compartment will shut down in conjunction with the system to achieve electrical isolation between the photovoltaic DC side and the aluminum electrolysis DC side.

[0014] In conjunction with the second aspect, preferably, the positive busbar protection cabinet, the negative busbar protection cabinet, the positive busbar fuse cabinet, and the negative busbar fuse cabinet are each equipped with a constant temperature anti-condensation device, which automatically activates when the humidity inside the cabinet exceeds 75%RH.

[0015] In conjunction with the first aspect, preferably, the positive busbar protection cabinet, the negative busbar protection cabinet, the positive busbar fuse cabinet, and the negative busbar fuse cabinet are each provided with an auxiliary grounding terminal, and the grounding resistance is not greater than 4 Ω.

[0016] Compared with the prior art, the advantages or beneficial effects of the embodiments of this application include at least the following: The DC microgrid system provided in this application forms a complete power loop by independently connecting the photovoltaic DC positive and negative busbars to the aluminum electrolysis DC busbar. On the one hand, the cabinet-style structural design and overhead isolation from the post insulators significantly improve the system's electrical safety and environmental adaptability. Each functional cabinet is independently set up, allowing for rapid location of the faulty cabinet in case of a fault, facilitating operation and maintenance and fault handling. On the other hand, the protection cabinet and fuse cabinet form a two-level protection node both physically and electrically. When a fault occurs at any level, this series structure naturally prevents the fault from propagating to subsequent or preceding levels. This system not only eliminates the risk of short circuits between the positive and negative buses in the same cabinet but also improves insulation stability under complex operating conditions through a suspended insulation structure. Simultaneously, it ensures the safety of core equipment with the help of fast-acting fuses, ultimately achieving safe access of photovoltaic DC power in the aluminum electrolysis environment. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of a DC microgrid system according to an embodiment of this application; Figure 2 This is a schematic diagram of the positive bus protection cabinet in a DC microgrid system according to an embodiment of this application; Explanation of reference numerals in the attached drawings: 1-Prefabricated cabin, 2-Positive busbar protection cabinet, 3-Negative busbar protection cabinet, 4-Positive busbar fuse cabinet, 5-Negative busbar fuse cabinet, 6-Post insulator, 7-Aluminum electrolytic DC positive busbar, 8-Aluminum electrolytic DC negative busbar, 9-Aluminum electrolytic cell, 10-Insulation monitoring module, 11-First disconnecting switch, 12-Second disconnecting switch, 13-Fuse, 14-Power conversion module, 15-Constant temperature anti-condensation device, 16-Auxiliary grounding terminal, 17-Photovoltaic module, 18-Combiner box. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0020] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0021] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0022] Furthermore, the terms "installation," "setup," "equipped with," "connection," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0023] Furthermore, the terms "first," "second," etc., are primarily used to distinguish different devices, components, or parts (which may be the same or different in specific type and construction), and are not intended to indicate or imply the relative importance or quantity of the indicated devices, components, or parts. Unless otherwise stated, "a plurality of" means two or more.

[0024] It should be noted that in aluminum electrolysis production sites, photovoltaic DC power needs to be directly connected to the aluminum electrolysis DC microgrid system to avoid the multiple energy conversion losses caused by the rectification path within the plant, which is a consequence of traditional photovoltaic AC grid connection. In existing technologies, the positive and negative busbars are often housed in the same protection cabinet. In the high-temperature, high-humidity, dusty, and corrosive gas environment of an electrolysis workshop, the busbar insulation layer is prone to accelerated aging and damage, leading to short circuits between the positive and negative terminals or to ground within the cabinet, causing equipment damage or even safety accidents. Furthermore, conventional grounded cabinet structures cannot block leakage current paths, relying solely on passive monitoring and delayed actions, which is insufficient to achieve safety.

[0025] In a first aspect, embodiments of this application provide a DC microgrid system for photovoltaic-connected electrolytic aluminum, comprising: The prefabricated compartment (1) is used to convert the light energy collected by the photovoltaic panel into photovoltaic DC power, including a negative DC output terminal and a positive DC output terminal; Positive bus protection cabinet (2), the input end of the positive bus protection cabinet (2) is connected to the positive DC output end of the prefabricated cabin (1), the output end is connected to the input end of the positive bus fuse cabinet (4), and the output end of the positive bus fuse cabinet (4) is electrically connected to the aluminum electrolysis DC positive bus (7). The negative busbar protection cabinet (3) has its input end connected to the negative DC output end of the prefabricated cabin (1), and its output end connected to the input end of the negative busbar fuse cabinet (5). The output end of the negative busbar fuse cabinet (5) is electrically connected to the aluminum electrolytic DC negative busbar (8). The post insulator (6) is provided at the bottom of the positive bus protection cabinet (2), the positive bus fuse cabinet (4), the negative bus protection cabinet (3), and the negative bus fuse cabinet (5). The aluminum electrolysis DC positive bus (7) and the aluminum electrolysis DC negative bus (8) are connected to multiple aluminum electrolysis cells (9).

[0026] like Figure 1 As shown, this application provides a DC microgrid system for photovoltaic access in electrolytic aluminum, applied to an electrolytic aluminum plant. The plant's aluminum electrolysis series current is 400 kA, the number of aluminum electrolysis cells (9) connected in series is 288, and the rated voltage of the DC bus is 1500 V. The system includes a prefabricated cabin (1), a positive bus protection cabinet (2), a negative bus protection cabinet (3), a positive bus fuse cabinet (4), a negative bus fuse cabinet (5), post insulators (6), and auxiliary equipment.

[0027] In this embodiment, the prefabricated cabin (1) has dimensions of 6 m × 3 m × 3 m and integrates a standardized prefabricated power unit with photovoltaic current collection, DC / DC conversion, islanding detection, anti-reverse current control, and communication interface. An MPPT controller can be optionally installed inside to improve the power generation efficiency of the photovoltaic side. The internally integrated power conversion module (14) consists of multiple DC / DC converters connected in parallel, with a total rated power of 20 MW. It is used to convert the DC power output from the photovoltaic array, with a voltage range of 750-1500 V and a rated output current of not less than 2500 A, into DC power that matches the voltage of the aluminum electrolysis busbar, with a rated voltage of 1500 V. The bottom of the prefabricated cabin (1) is provided with a positive DC output terminal and a negative DC output terminal, both of which are led out using copper busbars.

[0028] In this embodiment, the positive busbar protection cabinet (2) and the negative busbar protection cabinet (3) are both single-input single-output structures with cabinet dimensions of 2000 mm × 1200 mm × 600 mm. The cabinet is formed by welding aluminum-zinc coated steel plate with a thickness of not less than 2.5 mm and a protection level of not less than IP54. Its input end is equipped with a copper-aluminum transition terminal adapted to the positive output end of the prefabricated compartment (1). After the terminal is crimped, a silicone rubber heat-shrinkable insulating sleeve is installed. The input end of the positive busbar protection cabinet (2) is connected to the positive DC output end of the prefabricated compartment (1) through a copper busbar, and the output end is connected to the input end of the positive busbar fuse cabinet (4) through a copper busbar. The input end of the negative busbar protection cabinet (3) is connected to the negative DC output end of the prefabricated compartment (1) through a copper busbar, and the output end is connected to the input end of the negative busbar fuse cabinet (5). The two cabinets are arranged independently in space, with a center-to-center distance of 2.0 m, to ensure that the positive and negative busbar paths do not intersect or share a busbar channel throughout the entire process.

[0029] In this embodiment, the positive busbar fuse cabinet (4) and the negative busbar fuse cabinet (5) have cabinet dimensions of 2000 mm × 800 mm × 600 mm. One set of fuses (13) is installed inside the positive busbar fuse cabinet (4), each with a rated current of 200 kA and a fusing time ≤ 4 ms; the same set of fuses is installed inside the negative busbar fuse cabinet (5), with the same parameters: rated current of 200 kA and fusing time ≤ 4 ms. The fuses are installed on independent insulating supports inside the cabinet, maintaining an air clearance ≥ 150 mm from the metal frame of the cabinet. The output terminal of the positive busbar fuse cabinet (4) is electrically connected to the aluminum electrolytic DC positive busbar (7), and the output terminal of the negative busbar fuse cabinet (5) is electrically connected to the aluminum electrolytic DC negative busbar (8).

[0030] In this embodiment, the post insulator (6) is preferably a solid post insulator made of composite material, with models FZSW-10 / 20 or FZSW-20 / 31.5, a rated voltage of not less than 10 kV, a bending failure load of not less than 20 kN, and a height of 150 mm-250 mm; at least 4 post insulators (6) are provided at the bottom of each cabinet, arranged in a rectangular shape, such as Figure 2 As shown. In practical applications, specific values ​​can be selected within this range according to the flatness of the ground, the height of the cable entry, and the clearance requirements of the maintenance channel. This application embodiment does not impose any special limitations on this. The support insulator (6) not only provides mechanical support, but also enables the entire cabinet to form a high-impedance insulation isolation with the ground, constructing a suspended structure, and completely blocking the leakage current path between the high-voltage busbar inside the cabinet and the ground, so that the insulation monitoring module (10) has the premise of effective monitoring.

[0031] Specifically, the installation position of the post insulator (6) can be adapted to the structural dimensions of the cabinet base. For example, it can be arranged within 100-300 mm from the edge of the base frame, or symmetrically distributed along the longitudinal center line of the base. This application embodiment does not make any special limitation on this.

[0032] Specifically, the aluminum electrolysis DC positive busbar (7) and the aluminum electrolysis DC negative busbar (8) can be T2 copper busbars with a cross-section of 300 mm × 30 mm or aluminum-magnesium alloy busbars with equivalent conductivity, and the surface is treated with tin plating or sprayed with insulating paint; the two are laid parallel to each other in the longitudinal direction of the electrolysis plant, and the net distance between the phases is not less than 600 mm; each section of busbar is reliably connected to the anode / cathode interface of multiple aluminum electrolysis cells (9) through multi-point soft connection (e.g., tin-plated copper braided strip); the overall design current carrying capacity of the busbar system is not less than 50 kA, and the voltage fluctuation range is controlled within ±5% of the rated value.

[0033] In this embodiment, the insulation monitoring module (10) is installed in both the positive busbar protection cabinet (2) and the negative busbar protection cabinet (3) to monitor the leakage current of the positive busbar to ground and the negative busbar to ground, respectively. The insulation monitoring module (10) adopts the DC injection method, with a sampling frequency of not less than 100 Hz, a measurement range of 0.1 mA to 100 mA, and a resolution of 0.01 mA. The internal first threshold is set to 1 mA and the second threshold is set to 10 mA. When the leakage current at any monitoring point reaches 1 mA and is less than 10 mA, an early warning signal is triggered, and the operation and maintenance personnel are notified through the on-site sound and light alarm and the remote monitoring system to carry out preventive maintenance operations such as cleaning the cabinet, tightening the connection points, and checking the surface condition of the insulation components. When the leakage current reaches 10 mA, the first disconnect switch (11) and the first disconnect switch (12) are triggered to open simultaneously, cutting off the electrical connection between the photovoltaic side and the electrolytic aluminum side. The control circuits of the first disconnecting switch (11) and the first disconnecting switch (12) are powered by independent power supplies and have electrical isolation to prevent the protection function from being downgraded due to the failure of either disconnecting switch to operate; their operation does not depend on external communication networks or upper-level systems, thereby greatly improving the determinism and timeliness of the protection response.

[0034] Specifically, the post insulator (6) structurally cuts off the path between the cabinet and the ground, forming a local floating potential; the insulation monitoring module (10) serves as the status feedback terminal of the floating system, continuously sensing the residual leakage current under the floating potential; the two work together to change the insulation protection strategy from a traditional response after a fault occurs to an early warning during the insulation deterioration process, significantly improving the system's adaptability to insulation failure caused by high temperature, high humidity, corrosive gases, etc. in the environment.

[0035] In this embodiment, the first disconnecting switch (11) and the first disconnecting switch (12) are connected in series between the positive bus protection cabinet (2) and the positive bus fuse cabinet (4), and the first disconnecting switch (12) is connected in series between the negative bus protection cabinet (3) and the negative bus fuse cabinet (5). The disconnecting switches are DC fast circuit breakers with a rated current of 4 kA, a breaking capacity of 100 kA, and a tripping time of ≤20 ms.

[0036] Specifically, under normal operating conditions, both the first disconnect switch (11) and the first disconnect switch (12) are in the closed state, and the photovoltaic DC power is stably delivered to the aluminum electrolysis DC bus through the positive and negative dual paths. When the system enters the maintenance mode, the monitoring background issues a maintenance isolation command, and the first disconnect switch (11) and the first disconnect switch (12) perform the opening action simultaneously, so that the photovoltaic side and the electrolytic aluminum load side are completely electrically isolated. At this time, the prefabricated cabin (1) can be shut down and debugged separately, while the electrolytic aluminum production circuit is not affected. When an abnormal working condition that requires rapid disconnection occurs, such as the insulation monitoring module (10) triggering an early warning, the fuse cabinet temperature exceeding the limit, or communication interruption, the bipolar disconnection process is automatically started. The two switches complete the opening within milliseconds, blocking the transmission of fault energy to the load side, and gaining a critical time window for subsequent fault diagnosis and handling.

[0037] Specifically, under normal system operation, the fuses in the positive bus fuse cabinet (4) and the negative bus fuse cabinet (5) are in the conducting state, forming a continuous current path together with the first disconnect switch (11) and the first disconnect switch (12). The melting time of the fuse (13) (≤4 ms) is less than the opening time of the disconnect switch (≤20 ms). When a short circuit occurs in the system, the short circuit current rises instantaneously. When an overcurrent fault occurs but the fault current is less than the breaking capacity of the disconnecting switch (less than or equal to 3600 A), the first disconnecting switch (11) and the first disconnecting switch (12) complete the tripping within 20 ms to achieve fault isolation. When an extremely large short circuit current (greater than 3600 A) exceeds the breaking capacity of the disconnecting switch, the fuse (13) melts and extinguishes the arc within 4 ms. At this time, the disconnecting switch may only be in the initial tripping stage or has not yet acted. However, since the fuse has cut off the circuit, the subsequent arc cannot be maintained, thus avoiding the risk of the disconnecting switch failing under over-limit conditions. This two-level response mechanism covers all faults and significantly improves the safety and timeliness of system protection.

[0038] Specifically, a photovoltaic module (17) and a combiner box (18) are provided in front of the prefabricated cabin (1). The combiner box (18) combines the DC power output from multiple photovoltaic modules (17) and outputs it to the prefabricated cabin (1). The prefabricated cabin (1) is equipped with a power conversion module (14) that can regulate the voltage, adapt the power, or set the power quality of photovoltaic DC power. Its specific configuration can be a DC / DC boost converter, a DC / DC bidirectional converter, or an intelligent DC conversion device with islanding detection and fast shutdown functions. The input end of the module is directly connected to the positive and negative DC busbars of the photovoltaic DC in the prefabricated cabin (1), and the output end is coupled to the positive DC output end and the negative DC output end of the prefabricated cabin (1). Its control logic is embedded in the controller of the prefabricated cabin (1) and establishes a bidirectional signal connection with the monitoring units in the positive busbar protection cabinet (2), negative busbar protection cabinet (3), positive busbar fuse cabinet (4), and negative busbar fuse cabinet (5) through industrial Ethernet or RS-485 bus. In this application, the power conversion module (14) serves as the energy regulation and safety exit node on the photovoltaic DC side. It does not participate in the constant current power supply process of the aluminum electrolysis cell (9) and only performs active blocking and shutdown actions when the system-level fault criteria are met, thereby cutting off the source of photovoltaic energy injection.

[0039] In this embodiment, the constant temperature anti-condensation device (15) has a semiconductor dehumidifier installed on the top of each cabinet. When the humidity sensor inside the cabinet detects that the humidity exceeds 75% RH, it automatically starts to control the humidity inside the cabinet below 60% RH. The closed-loop control device, which integrates a temperature and humidity sensor, a heating unit, and a small dehumidification module, is used to actively regulate the temperature and humidity of the local space inside the cabinet. The temperature and humidity sensor of this device collects the relative humidity and temperature data of the air inside the cabinet in real time. When the relative humidity is detected to be continuously higher than 75% RH, the controller automatically starts the heating unit or the dehumidification module to make the dew point temperature of the air inside the cabinet lower than the lowest surface temperature of the current environment, thereby inhibiting the condensation of water vapor on the surface of electronic components. The starting threshold of 75% RH for the constant temperature anti-condensation device (15) can be adaptively adjusted according to the climatic characteristics of the actual installation environment and the sealing level of the cabinet.

[0040] In this embodiment, the auxiliary grounding terminal (16) is provided on the outside of each cabinet, and the measured grounding resistance is 2.5 Ω. During maintenance, the cabinet is reliably connected to the main grounding grid through the grounding wire to ensure the safety of maintenance personnel. The auxiliary grounding terminal (16) is a metal conductive interface set in an easily accessible position on the side wall or bottom of each cabinet shell. Its structure can be an M12 threaded copper terminal, a tin-plated copper busbar lead-out end, or a crimp-type quick grounding buckle. The auxiliary grounding terminal (16) is used to establish a low-impedance electrical connection between the cabinet shell and the external grounding system during equipment maintenance, fault diagnosis, or abnormal operating conditions, thereby discharging static charge, induced voltage, or leakage current to prevent electric shock hazards when maintenance personnel come into contact with the cabinet.

[0041] Specifically, the power conversion module (14) in the prefabricated cabin (1) is connected to the fault signals of the positive bus protection cabinet (2), negative bus protection cabinet (3), positive bus fuse cabinet (4), and negative bus fuse cabinet (5) via hard wiring. When the system detects faults that cannot be quickly eliminated, such as insulation monitoring tripping, disconnecting switch tripping, or fuse blowing, the power conversion module (14) performs a linkage shutdown within 50 ms, stops outputting energy to the bus, and realizes rapid electrical isolation between the photovoltaic DC side and the aluminum electrolysis DC side.

[0042] Specifically, the technical principle of this application is as follows: the DC power generated by the photovoltaic module (17) is fed into the prefabricated compartment (1) after being combined, and voltage matching and power quality regulation are completed; the DC power output from the positive output terminal of the prefabricated compartment (1) is protected by the positive bus protection cabinet (2) and then enters the positive bus fuse cabinet (4). In this cabinet, if a small current overload fault occurs, the first disconnect switch (11) on the branch of the positive bus protection cabinet (2) will disconnect the fault; if a large short circuit current occurs, the fuse (13) in the positive bus fuse cabinet (4) will blow first; the protected positive DC power is finally connected to the aluminum electrolytic DC positive bus (7); similarly, the DC power output from the negative output end of the prefabricated cabin (1) is connected to the aluminum electrolytic DC negative bus (8) after passing through the negative bus protection cabinet (3) and the negative bus fuse cabinet (5); the two paths operate completely independently and do not interfere with each other; each cabinet is suspended above the foundation due to the bottom support insulator (6), and a stable insulation barrier is formed between the high voltage busbar inside the cabinet and the cabinet shell, which significantly improves the long-term insulation reliability of the system in harsh industrial environments.

[0043] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0044] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of this application.

Claims

1. A DC microgrid system for photovoltaic access in electrolytic aluminum, characterized in that, include: The prefabricated compartment is used to convert the light energy collected by the photovoltaic panels into photovoltaic DC electricity, including a negative DC output terminal and a positive DC output terminal; A positive bus protection cabinet, wherein the input terminal of the positive bus protection cabinet is connected to the positive DC output terminal of the prefabricated compartment, the output terminal is connected to the input terminal of the positive bus fuse cabinet, and the output terminal of the positive bus fuse cabinet is electrically connected to the aluminum electrolysis DC positive bus. The negative busbar protection cabinet has its input terminal connected to the negative DC output terminal of the prefabricated compartment, and its output terminal connected to the input terminal of the negative busbar fuse cabinet. The output terminal of the negative busbar fuse cabinet is electrically connected to the aluminum electrolysis DC negative busbar. The post insulator is provided at the bottom of the negative busbar protection cabinet, the negative busbar fuse cabinet, the positive busbar protection cabinet, and the positive busbar fuse cabinet, respectively. The aluminum electrolysis DC positive bus and the aluminum electrolysis DC negative bus are connected to multiple aluminum electrolysis cells.

2. The DC microgrid system for photovoltaic access to electrolytic aluminum as described in claim 1, characterized in that, Also includes: An insulation monitoring module is installed inside the negative busbar protection cabinet and / or the positive busbar protection cabinet to monitor the leakage current between the high-voltage busbar inside the protection cabinet and the cabinet shell in real time.

3. The DC microgrid system for photovoltaic access to electrolytic aluminum according to claim 1, characterized in that, A first disconnecting switch is connected in series between the positive bus protection cabinet and the positive bus fuse cabinet; A second disconnecting switch is connected in series between the negative busbar protection cabinet and the negative busbar fuse cabinet.

4. The DC microgrid system for photovoltaic access to electrolytic aluminum according to claims 2 and 3, characterized in that, The insulation monitoring module is equipped with a first threshold and a second threshold; and the first threshold is less than the second threshold. When the insulation monitoring module detects that the leakage current is greater than or equal to the first threshold and less than the second threshold, it triggers an early warning signal; When the insulation monitoring module detects that the leakage current is greater than or equal to the second threshold, it triggers the first disconnect switch and the second disconnect switch to trip simultaneously.

5. The DC microgrid system for photovoltaic access in electrolytic aluminum according to claim 3, characterized in that, Both the positive busbar fuse cabinet and the negative busbar fuse cabinet are equipped with fuses. The fuse's melting time is configured to be less than the opening time of the first or second disconnecting switch; If an overcurrent fault occurs that exceeds the rated current of the first or second disconnecting switch, the first and second disconnecting switches will trip simultaneously. If a short-circuit current fault exceeding the breaking capacity of the first or second disconnecting switch occurs, the fuse shall blow in priority over the first or second disconnecting switch.

6. The DC microgrid system for photovoltaic access in electrolytic aluminum according to claim 1, characterized in that, The positive busbar protection cabinet and the negative busbar protection cabinet are spatially independent of each other, and the distance between the two cabinets is not less than 1.5m.

7. The DC microgrid system for photovoltaic access to electrolytic aluminum according to claim 1, characterized in that, The number of post insulators at the bottom of each cabinet shall be at least 4; The rated voltage of the post insulator shall not be less than 10 kV, and the bending failure load shall not be less than 20 kN; The height of the post insulator is 150-250 mm.

8. The DC microgrid system for photovoltaic access to electrolytic aluminum according to claim 1, characterized in that, The prefabricated cabin is equipped with a power conversion module; The prefabricated compartment is connected to the positive bus protection cabinet, the negative bus protection cabinet, the negative bus fuse cabinet, and the positive bus fuse cabinet via signal connection. When the system detects a fault that cannot be quickly eliminated, the power conversion module in the prefabricated compartment will shut down in conjunction with the system to achieve electrical isolation between the photovoltaic DC side and the aluminum electrolysis DC side.

9. The DC microgrid system for photovoltaic access in electrolytic aluminum according to claim 1, characterized in that, The positive busbar protection cabinet, the negative busbar protection cabinet, the positive busbar fuse cabinet, and the negative busbar fuse cabinet are each equipped with a constant temperature anti-condensation device, which automatically activates when the humidity inside the cabinet exceeds 75% RH.

10. The DC microgrid system for photovoltaic access in electrolytic aluminum according to claim 1, characterized in that, The positive busbar protection cabinet, the negative busbar protection cabinet, the positive busbar fuse cabinet, and the negative busbar fuse cabinet are each equipped with an auxiliary grounding terminal, and the grounding resistance is not greater than 4 Ω.

Images