An underground mine alternating current and direct current hybrid intelligent power supply and distribution system and control method

Abstract

This invention belongs to the field of power supply and distribution technology, and particularly relates to an AC / DC hybrid intelligent power supply and distribution system and control method for underground coal mines. The system includes: a four-port power electronic transformer on the surface and underground; the 3300V medium-voltage AC port, 10kV medium-voltage AC port, 1500V low-voltage DC port, and 10kV medium-voltage DC port of the surface four-port power electronic transformer are respectively connected to the 3300V AC bus, the 10kV AC bus, the 1500V DC bus, and the 10kV DC bus via switches S1, S2, S3, and S4, respectively. The underground four-port power electronic transformer has its 3300V medium-voltage AC port, 10kV medium-voltage AC port, 1500V low-voltage DC port, and 10kV medium-voltage DC port connected to the 10kV DC bus, 10kV AC bus, 1500V DC bus, and 3300V AC bus, respectively, via switches S5, S6, S7, and S8. The 10kV AC bus is connected to the 3300V AC bus via transformer T3 and switch S14. The 10kV DC bus is connected to the photovoltaic power generation system via switch S9. This invention can reduce energy consumption and ensure safe electricity use in production.

Description

Technical Field

[0001] This invention belongs to the field of power supply and distribution technology, and particularly relates to an AC / DC hybrid intelligent power supply and distribution system and control method for underground coal mines. Background Technology

[0002] Against the backdrop of low-carbon and energy-saving development, ground-based industrial power supply and distribution networks have gradually seen the emergence of various demonstration projects for park energy management that integrate AC / DC loads, energy storage, renewable energy, and traditional energy sources. These demonstration applications utilize DC interconnection or AC / DC hybrid technology to interconnect various AC / DC devices of different voltages and power levels, including renewable energy, energy storage, and loads, achieving good results in new energy utilization and energy conservation. Meanwhile, with the continuous increase in underground coal mining volume and the growing number of high-power coal mining equipment, the overall power demand of coal mines is also increasing, leading to increased energy consumption in both the power supply and consumption stages of the coal mine power grid. Specifically, in the current AC power supply and distribution field of underground coal mines, AC power supply networks suffer from problems such as large reactive power losses, high harmonic ratios leading to protection malfunctions, and transformer capacity saturation during peak electricity consumption periods. Meanwhile, the increased demand for DC power supply in underground mines (such as battery-powered vehicle fast charging, fast-swapping devices, and communication base stations) requires conversion from AC to DC, increasing energy consumption. Therefore, a smart hybrid power supply and distribution network with DC as the primary power source and AC as a secondary power source is needed. DC power should be used in DC power consumption and long-distance transmission applications to fully leverage the advantages of DC power supply, saving energy and reducing consumption. In the event of a DC power supply failure, the network should automatically switch back to the mine's original AC power supply mode to ensure smooth production, achieving both energy optimization and ensuring safe electricity use for production. Summary of the Invention

[0003] This invention overcomes the shortcomings of existing AC power supply and distribution technologies in underground coal mines. The technical problem to be solved is to provide an AC / DC hybrid intelligent power supply and distribution system and control method for underground coal mines, so as to realize the coordinated control of ground and underground substations, and achieve the effect of fully absorbing renewable energy and reducing mining energy consumption.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: an AC / DC hybrid intelligent power supply and distribution system for underground coal mines, comprising: a surface four-port power electronic transformer U1, an underground four-port power electronic transformer U2, a transformer T3, and a switch S14;

[0005] The 3300V medium-voltage AC port of the ground four-port power electronic transformer U1 is connected to the 3300V AC bus via switch S1, the 10kV medium-voltage AC port is connected to the 10kV AC bus via switch S2, the 1500V low-voltage DC port is connected to the 1500V DC bus via switch S3, and the 10kV medium-voltage DC port is connected to the 10kV DC bus via switch S4.

[0006] The 3300V medium-voltage AC port of the downhole four-port power electronic transformer U2 is connected to the 3300V AC bus via switch S8, the 10kV medium-voltage AC port is connected to the 10kV AC bus via switch S6, the 1500V low-voltage DC port is connected to the 1500V DC bus via switch S7, and the 10kV medium-voltage DC port is connected to the 10kV DC bus via switch S5.

[0007] The 10kV AC busbar is connected to the 3300V AC busbar via transformer T3 and switch S14;

[0008] The 10kV DC bus is connected to the DC / DC conversion module of the photovoltaic power generation system via switch S9.

[0009] The described AC / DC hybrid intelligent power supply and distribution system for underground coal mines also includes two independent 35kV power grid inputs. The first 35kV power grid input is connected to the 10kV AC bus via transformer T1 and switch S10. The second 35kV power grid input is connected to the standby 10kV AC bus via transformer T2 and switch S11. The 10kV AC bus and the standby 10kV AC bus are connected via switches S12 and S13.

[0010] The aforementioned intelligent AC / DC hybrid power supply and distribution system for underground coal mines further includes wind power generation equipment, gas exhaust gas oxidation power generation equipment, and an energy storage system. The wind power generation equipment and the gas exhaust gas oxidation power generation equipment are connected to a 3300V AC bus; the energy storage system and the DC load are connected to a 1500V DC bus; and the photovoltaic power generation system is connected to the 10kV DC bus via a DC-DC conversion module and switch S9.

[0011] The photovoltaic power generation system is a centralized photovoltaic power generation system.

[0012] The aforementioned AC / DC hybrid intelligent power supply and distribution system for underground coal mines also includes a transformer T4. The 3300V AC bus is connected to an 1140V AC bus via the transformer T4. The 1140V AC bus is used to supply power to the equipment and electric auxiliary transport vehicles at the tunneling face.

[0013] Furthermore, the present invention also provides a control method for an AC / DC hybrid intelligent power supply and distribution system in underground coal mines, comprising:

[0014] State (1): When both the ground four-port power electronic transformer U1 and the underground four-port power electronic transformer U2 are in normal working condition, switch S6 is disconnected and switches S1~S5 and S7~S8 are closed; the control strategies for each port of the ground four-port power electronic transformer U1 are as follows: the 10kV medium-voltage AC port implements the grid-connected following operation strategy, and the power of the mains network is determined by the sum of the power of the other ports, presenting an overall power balance of the four ports; the 3300V medium-voltage AC port implements voltage source control; the 1500V low-voltage DC port implements voltage source control; the 10kV medium-voltage DC port implements voltage source control to keep the voltage of the 10kV DC bus stable;

[0015] The control strategies for each port of the underground four-port power electronic transformer U2 are as follows: the 10kV medium-voltage DC port adopts a droop control mode, which, together with the 10kV medium-voltage DC port of the surface four-port power electronic transformer U1, stabilizes the voltage and power balance of the 10kV DC bus; the 3300V medium-voltage AC port adopts a voltage source control mode, which supplies power to the coal mining face equipment connected to the 3300V AC bus, and after passing through a first-stage transformer to 1140V, supplies power to the tunneling face; the 1500V low-voltage DC port implements a voltage source control mode, which supplies power to the underground DC load; the 10kV medium-voltage AC port is in a locked state.

[0016] The power generation devices connected to the 3300V AC bus operate under maximum power control and are connected to the 3300V AC bus. The ground and underground energy storage devices connected to the 1500V DC bus cooperate with the new energy output to perform peak shaving and valley filling, and the energy storage priority of underground energy storage is greater than that of ground energy storage. The photovoltaic power generation system connected to the 10kV DC bus operates under maximum power control, and the generated power is transmitted in the following order: underground load, underground energy storage, ground load, ground energy storage and connection to the municipal power grid.

[0017] State (2): When both the surface four-port power electronic transformer U1 and the underground four-port power electronic transformer U2 are faulty, disconnect switches S1-S9 to lock each port of the two four-port power electronic transformers, close switch S14, and use the 10kV AC bus to supply power to the underground equipment.

[0018] State (3): When the ground four-port power electronic transformer U1 fails and stops, and the underground four-port power electronic transformer U2 is working normally, disconnect switches S1 to S4 and close switches S5 to S9 to lock all ports of the ground four-port power electronic transformer U1. The control strategies for each port of the underground four-port power electronic transformer U2 are as follows: the 10kV medium-voltage AC port implements the grid-connected following operation strategy, and the power of the mains network depends on the power of the other ports, and the overall power balance of the four ports is presented; the 3300V medium-voltage AC port implements voltage source control, and the power is determined by the load; the 1500V low-voltage DC port implements voltage source control; the 10kV medium-voltage DC port adopts droop control of the 10kV DC bus voltage; the underground energy storage device performs emergency energy storage according to the charging and discharging strategy and charge and discharge management according to the peak and valley electricity price, and provides the other DC equipment for use after being stepped down by the DC / DC device;

[0019] State (4): When the underground four-port power electronic transformer U2 fails and shuts down, and the surface four-port power electronic transformer U1 is working normally, close switches S1~S4 and S9, and open switches S5~S8 to lock all ports of the underground four-port power electronic transformer U2. The control strategies for each port of the surface four-port power electronic transformer U1 are as follows: the 10kV AC port implements the grid-connected follow-up operation strategy; the 3300V medium-voltage AC port implements voltage source control; the 1500V low-voltage DC port implements voltage source control; the 10kV medium-voltage DC port implements voltage source control to stabilize the voltage of the 10kV DC bus; the power generation device connected to the 3300V AC bus operates according to the maximum power generation control and is connected to the 3300V AC bus; the ground energy storage device connected to the 1500V DC bus cooperates with the new energy output to perform peak shaving and valley filling; the photovoltaic power generation system connected to the 10kV DC bus adopts the maximum power generation control operation.

[0020] The intelligent power supply and distribution system also includes two independent 35kV power grid inputs. The first 35kV power grid input is connected to the 10kV AC bus via transformer T1 and switch S10. The second 35kV power grid input is connected to the backup 10kV AC bus via transformer T2 and switch S11. The 10kV AC bus and the backup 10kV AC bus are connected via switches S12 and S13. The control method also includes:

[0021] When the 10kV AC busbar is normal, close switches S10 and S11 and open switches S12 and S13.

[0022] When the 10kV AC bus fails, the control strategy of closing switches S11, S12 and S13, opening switch S10, switching to the standby 10kV AC bus, and maintaining the state (1) of the ground four-port power electronic transformer U1 and the underground four-port power electronic transformer U2.

[0023] When the underground four-port power electronic transformer U2 malfunctions, switch S14 is closed; when the underground four-port power electronic transformer U2 is functioning normally, switch S14 is opened.

[0024] When both the surface four-port power electronic transformer U1 and the underground four-port power electronic transformer U2 are in normal working condition, if a fault occurs in the 10kV DC bus transmission, switch S6 will be closed to enable the 10kV medium-voltage AC port of the underground four-port power electronic transformer U2 to supply power to the underground working face load.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] 1. This invention provides an AC / DC hybrid intelligent power supply and distribution system and control method for underground coal mines. It employs two identical four-port power electronic transformers as the DC power transmission architecture, symmetrically arranged above and below ground. The two symmetrically arranged four-port power electronic transformers are interconnected via their respective DC ports, thereby enabling the surface and underground substations to be interconnected through a dual-bus topology of existing AC and newly added DC power. This allows for the hybrid AC / DC transmission of power between the surface and underground substations. The surface substation simultaneously collects power from surface renewable energy sources, energy storage, the power grid, and surface loads. The underground substation simultaneously ensures the power needs of various working areas underground through AC and DC ports.

[0027] 2. This invention achieves the full utilization of renewable energy and reduces mining energy consumption through the coordinated control of four-port power electronic transformers on the surface and underground. The power supply and distribution scheme described can be applied to various coal mine scenarios to realize power transmission at various voltage and power levels, and can also be extended to similar application scenarios.

[0028] 3. This invention utilizes the coordinated operation of switching switches at each port of two four-port power electronic transformers to form a hybrid AC / DC intelligent power distribution network in conjunction with the existing AC power supply lines. Compared to the existing dual-circuit AC power supply scheme in mining areas, this invention effectively reduces AC line losses while simultaneously reducing DC source inverter losses, while providing dual-circuit redundant power supply. It can transmit electrical energy via DC, eliminating line losses and harmonic propagation caused by AC transmission; it can conveniently and efficiently apply renewable energy from the ground directly to power underground coal mining equipment, avoiding waste caused by transmission through the public power grid; and the automatic switching between DC and AC transmission modes optimizes energy consumption in coal mine production and ensures safe production.

[0029] 4. The present invention provides an AC / DC hybrid intelligent power supply and distribution system and control method for underground coal mines. Utilizing switching switches and connecting cables for each line, it can adaptively switch between various operating states. It combines the advantages of new energy AC microgrids and DC microgrids, while also considering the power load demands of underground coal mines and existing AC power supply schemes. It represents an upgrade and transformation of the underground coal mine power supply and distribution scheme, rather than a complete reconstruction, thus saving on construction investment costs. Therefore, the present invention possesses considerable technical and economic advantages. Attached Figure Description

[0030] Figure 1 The circuit diagram of an AC / DC hybrid intelligent power supply and distribution system for underground coal mines is provided in an embodiment of the present invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1

[0033] like Figure 1 As shown, Embodiment 1 of the present invention provides an AC / DC hybrid intelligent power supply and distribution system for underground coal mines, including: a ground four-port power electronic transformer U1, an underground four-port power electronic transformer U2, a transformer T3, and switches S14 and S9.

[0034] Specifically, the 3300V medium-voltage AC port of the ground-based four-port power electronic transformer U1 is connected to the 3300V AC bus via switch S1, the 10kV medium-voltage AC port is connected to the 10kV AC bus via switch S2, the 1500V low-voltage DC port is connected to the 1500V DC bus via switch S3, and the 10kV medium-voltage DC port is connected to the 10kV DC bus via switch S4.

[0035] Specifically, the 3300V medium-voltage AC port of the downhole four-port power electronic transformer U2 is connected to the 3300V AC bus via switch S8, the 10kV medium-voltage AC port is connected to the 10kV AC bus via switch S6, the 1500V low-voltage DC port is connected to the 1500V DC bus via switch S7, and the 10kV medium-voltage DC port is connected to the 10kV DC bus via switch S5.

[0036] The 10kV AC busbar is connected to the 3300V AC busbar via transformer T3 and switch S14.

[0037] The 10kV DC bus is connected to the DC / DC conversion module of the photovoltaic power generation system via switch S9.

[0038] Furthermore, such as Figure 1 As shown in the figure, the AC / DC hybrid intelligent power supply and distribution system for underground coal mines described in this embodiment also includes two independent 35kV power grid inputs. The first 35kV power grid input is connected to the 10kV AC bus through transformer T1 and switch S10. The second 35kV power grid input is connected to the spare 10kV AC bus through transformer T2 and switch S11. The 10kV AC bus and the spare 10kV AC bus are connected through switches S12 and S13.

[0039] Furthermore, such as Figure 1 As shown in the figure, an AC / DC hybrid intelligent power supply and distribution system for underground coal mines in this embodiment also includes wind power generation equipment, gas exhaust wind oxidation power generation equipment, and energy storage system. The wind power generation equipment and the gas exhaust wind oxidation power generation equipment are connected to a 3300V AC bus; the energy storage system and the DC load are connected to a 1500V DC bus.

[0040] Specifically, the photovoltaic power generation system is a centralized photovoltaic power generation system. The energy storage system includes an above-ground energy storage system and an underground energy storage system, which are respectively installed above ground and underground, and connected to a 1500V DC bus. In addition, the underground electrical equipment includes electric transport vehicles, underground charging piles, etc., and a 750V DC bus and a 240V DC bus are also installed underground.

[0041] Furthermore, such as Figure 1 As shown in the figure, an AC / DC hybrid intelligent power supply and distribution system for underground coal mines in this embodiment also includes a transformer T4. The 3300V AC bus is connected to an 1140V AC bus through the transformer T4. The 1140V AC bus is used to supply power to the equipment and electric auxiliary transport vehicles at the tunneling face. Specifically, the equipment at the fully mechanized mining face is powered by the 3300V AC bus; the equipment at the tunneling face, such as auxiliary transport vehicles, complete sets of tunneling face equipment, and supporting equipment at the tunneling face, is powered by the 1140V AC bus.

[0042] The working principle of this invention embodiment is as follows:

[0043] The power supply and distribution system of this invention includes a DC power supply system and an AC power supply system. The DC power supply system consists of two symmetrical four-port power electronic transformers connected by a DC bus. The 3300V medium-voltage AC port of the ground-based four-port power electronic device is connected to the 3300V AC bus via switch S1, providing power together with wind power generation devices and gas power generation devices. The 10kV medium-voltage AC port is connected to the 10kV AC bus via switch S2, forming a bidirectional AC power transmission path with the municipal power grid. The 1500V low-voltage DC port is connected to the 1500V DC bus via switch S3, forming a low-voltage DC microgrid together with ground-based energy storage devices and charging stations. The 10kV DC port is connected to the 10kV DC bus via switch S4, and this DC bus further... The system is connected to the photovoltaic power generation system via switch S9; the 10kV DC port of the underground four-port power electronic transformer U2 is connected to the 10kV DC bus via switch S5; the 10kV medium-voltage AC port is connected to the underground 10kV AC bus via switch S6, forming a bidirectional power transmission path with the existing underground AC power grid; the 1500V low-voltage DC port is connected to the 1500V DC bus via switch S7, forming an underground low-voltage DC microgrid together with the underground energy storage system and DC loads; the 3300V medium-voltage AC port is connected to the 3300V AC bus via switch S8, supplying power to the equipment in the fully mechanized mining face, while this bus generates an 1140V AC bus via a power frequency transformer, supplying power to the equipment and electric auxiliary transport vehicles in the tunneling face.

[0044] The AC power supply system consists of two independent 35kV mains inputs, each transforming into two 10kV AC busbars via power frequency transformer T1 and switch S10, and power frequency transformer T2 and switch S11, respectively, for use by surface equipment. These busbars then connect to the underground substation via their respective underground cables to supply the underground loads. One of the underground 10kV AC busbars is connected to the 3300V AC busbar via transformer T3 and switch S14. The AC power supply system connects to the DC power supply system at three nodes formed by switches S2, S6, and S14. The two independent AC busbars are connected via switches S12 and S13, respectively. If one AC busbar fails, the other can still connect to the DC grid, forming a stable AC / DC hybrid microgrid.

[0045] Example 2

[0046] Embodiment 2 of the present invention provides a control method for an AC / DC hybrid intelligent power supply and distribution system in underground coal mines as described in Embodiment 1. The states of the switching switches of each branch in the network are shown in Table 1, depending on the five operating states of the intelligent power supply and distribution system.

[0047] Table 1. Switch status at various locations under five operating states of the intelligent power supply and distribution network.

[0048]

[0049] Specifically, the control method in this embodiment includes the following methods.

[0050] State (1): When both the ground four-port power electronic transformer U1 and the underground four-port power electronic transformer U2 are in normal working condition, switch S6 is disconnected and switches S1~S5 and S7~S8 are closed; the control strategies for each port of the ground four-port power electronic transformer U1 are as follows: the 10kV medium-voltage AC port implements the grid-connected following operation strategy, and the exchange power with the mains network is determined by the sum of the power of the other ports of U1. Overall, U1 presents a power balance of the four ports; the 3300V medium-voltage AC port implements voltage source control; the 1500V low-voltage DC port implements voltage source control; the 10kV medium-voltage DC port implements voltage source control to keep the voltage of the 10kV DC bus stable;

[0051] The control strategies for each port of the underground four-port power electronic transformer U2 are as follows: the 10kV medium-voltage DC port adopts a droop control mode, which, together with the 10kV medium-voltage DC port of the surface four-port power electronic transformer U1, stabilizes the voltage and power balance of the 10kV DC bus; the 3300V medium-voltage AC port adopts a voltage source control mode, which supplies power to the coal mining face equipment connected to the 3300V AC bus, and after passing through a first-stage transformer to 1140V, supplies power to the tunneling face equipment; the 1500V low-voltage DC port implements a voltage source control mode, which supplies power to the underground DC load; the 10kV medium-voltage AC port is in a locked state.

[0052] The power generation devices connected to the 3300V AC bus operate under maximum power control and are connected to the 3300V AC bus. The ground and underground energy storage devices connected to the 1500V DC bus cooperate with the new energy output to perform peak shaving and valley filling, and the energy storage priority of underground energy storage is greater than that of ground energy storage. The photovoltaic power generation system connected to the 10kV DC bus operates under maximum power control, and the generated power is transmitted in the following order: underground load, underground energy storage, ground load, ground energy storage, and connection to the municipal power grid.

[0053] When both the surface four-port power electronic transformer U1 and the underground four-port power electronic transformer U2 are in normal working condition, if a fault occurs in the 10kV DC bus transmission, switch S6 will be closed to enable the 10kV medium-voltage AC port of the underground four-port power electronic transformer U2 to supply power to the underground working face load.

[0054] Operating state (1) is the normal operating state of the intelligent power supply and distribution scheme in coal mines. In this state, the four-port power electronic transformers on the ground and underground are operating normally. The loads are powered by AC and DC lines respectively. The goal is to make the most of the renewable energy on the ground and to make the DC form of power transmission as much as possible on the ground and underground. The characteristic of this operating state is that it is mainly based on the power change of the underground working load, combined with the output change of renewable energy, to adjust the charging and discharging period of energy storage, so as to minimize the net power absorbed from the grid.

[0055] State (2): When both the surface four-port power electronic transformer U1 and the underground four-port power electronic transformer U2 are faulty, disconnect switches S1-S9 to lock each port of the two four-port power electronic transformers, close switch S14, and use the 10kV AC bus to supply power to the underground equipment.

[0056] Operating state (2) is an abnormal operating state of the coal mine intelligent power supply and distribution scheme. The goal is to degrade the intelligent power supply and distribution network to the original AC power supply network when both four-port power electronic transformers fail and shut down, so as to ensure that the power load on the ground and underground can maintain normal operation. At this time, each port of the two four-port power electronic transformers is in a locked state. By closing switches S10 and S14, the working face load that was originally powered by the four-port power electronic transformer is supplied with power.

[0057] State (3): When the four-port power electronic transformer U1 on the ground fails and stops, and the four-port power electronic transformer U2 underground is working normally, disconnect switches S1 to S4 and close switches S5 to S9 to lock all ports of the four-port power electronic transformer U1 on the ground. The control strategies for each port of the four-port power electronic transformer U2 underground are as follows: the 10kV medium-voltage AC port implements the grid-connected following operation strategy, and the power of the mains network depends on the power of the other ports, and the overall power balance of the four ports is presented; the 3300V medium-voltage AC port implements voltage source control, and the power is determined by the load; the 1500V low-voltage DC port implements voltage source control; the 10kV medium-voltage DC port adopts droop control of the 10kV DC bus voltage; the underground energy storage device performs emergency energy storage according to the charging and discharging strategy and charge and discharge management according to the peak and valley electricity price, and provides the other DC equipment for use after being stepped down by the DC / DC device.

[0058] Operating status (3) is an abnormal operating status of the coal mine intelligent power supply and distribution scheme. The goal is to switch the intelligent power supply and distribution network to a partial AC and DC power supply network when the four-port power electronic transformer U1 on the ground fails and stops, and the four-port power electronic transformer U2 underground works normally, so as to ensure the normal operation of the power load on the ground and underground, while making the best use of photovoltaic power generation resources and underground energy storage resources.

[0059] State (4): When the underground four-port power electronic transformer U2 fails and shuts down, and the surface four-port power electronic transformer U1 is working normally, close switches S1~S4 and S9, and open switches S5~S8 to lock all ports of the underground four-port power electronic transformer U2. The control strategies for each port of the surface four-port power electronic transformer U1 are as follows: the 10kV AC port implements the grid-connected follow-up operation strategy; the 3300V medium-voltage AC port implements voltage source control; the 1500V low-voltage DC port implements voltage source control; the 10kV medium-voltage DC port implements voltage source control to stabilize the voltage of the 10kV DC bus; the power generation device connected to the 3300V AC bus operates according to the maximum power generation control and is connected to the 3300V AC bus; the ground energy storage device connected to the 1500V DC bus cooperates with the new energy output to perform peak shaving and valley filling; the photovoltaic power generation system connected to the 10kV DC bus adopts the maximum power generation control operation.

[0060] Operating status (4) is an abnormal operating status of the coal mine intelligent power supply and distribution scheme. The goal is to switch the intelligent power supply and distribution network to a partial AC and DC power supply network when the underground four-port power electronic transformer U2 fails and stops, and the ground four-port power electronic transformer U1 is working normally. This ensures that the power load on the ground and underground works normally, while making the best use of ground renewable energy power generation resources and energy storage resources.

[0061] Furthermore, in this embodiment, the intelligent power supply and distribution system also includes two independent 35kV grid inputs. The first 35kV grid input is connected to the 10kV AC bus via transformer T1 and switch S10, and the second 35kV grid input is connected to the spare 10kV AC bus via transformer T2 and switch S11. The 10kV AC bus and the spare 10kV AC bus are connected via switches S12 and S13. The control method also includes:

[0062] Operating state (5): When the 10kV AC bus fails, close switches S11, S12 and S13, open switch S10, switch to standby 10kV AC bus, and maintain the control strategy of the above state (1) for the ground four-port power electronic transformer U1 and the underground four-port power electronic transformer U2.

[0063] Operating state (5) is a backup normal operating state of the coal mine intelligent power supply and distribution scheme. The goal is to switch to another independent AC line to form a new hybrid power distribution network in the event of a fault in the AC line of the AC-DC hybrid power distribution network, so as to achieve the same operating effect as operating state 1 and ensure the normal operation of the power load on the ground and underground. At this time, by closing S11, S12 and S13 and opening S10 and S14, the AC power supply is switched from the S10 line to the S11 line, thereby realizing the reorganization of the AC-DC hybrid power distribution network.

[0064] In addition, it should be noted that when the 10kV AC bus is normal, close switches S10 and S11 and open switches S12 and S13.

[0065] In addition, in this embodiment, when the downhole four-port power electronic transformer U2 fails, switch S14 is closed; when the downhole four-port power electronic transformer U2 is normal, switch S14 is opened.

[0066] Furthermore, it should be noted that this invention is mainly designed for the energy-saving and consumption-reducing and intelligent power supply and distribution needs of surface and underground electrical loads in underground coal mines. For other similar scenarios of hybrid power distribution networks, including different numbers of ports, port voltages and capacities, this method can be referred to.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some 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 the embodiments of the present invention.

Claims

1. A hybrid AC / DC intelligent power supply and distribution system for underground coal mines, characterized in that, include: The surface four-port power electronic transformer U1, the underground four-port power electronic transformer U2, the transformer T3, and the switch S14; The 3300V medium-voltage AC port of the ground four-port power electronic transformer U1 is connected to the 3300V AC bus via switch S1, the 10kV medium-voltage AC port is connected to the 10kV AC bus via switch S2, the 1500V low-voltage DC port is connected to the 1500V DC bus via switch S3, and the 10kV medium-voltage DC port is connected to the 10kV DC bus via switch S4. The 3300V medium-voltage AC port of the downhole four-port power electronic transformer U2 is connected to the 3300V AC bus via switch S8, the 10kV medium-voltage AC port is connected to the 10kV AC bus via switch S6, the 1500V low-voltage DC port is connected to the 1500V DC bus via switch S7, and the 10kV medium-voltage DC port is connected to the 10kV DC bus via switch S5. The 10kV AC busbar is connected to the 3300V AC busbar via transformer T3 and switch S14; The 10kV DC bus is connected to the DC / DC conversion module of the photovoltaic power generation system via switch S9; it also includes two independent 35kV grid inputs. The first 35kV grid input is connected to the 10kV AC bus via transformer T1 and switch S10, and the second 35kV grid input is connected to the spare 10kV AC bus via transformer T2 and switch S11. The 10kV AC bus and the spare 10kV AC bus are connected via switches S12 and S13. It also includes wind power generation equipment, gas exhaust wind oxidation power generation equipment, and energy storage system. The wind power generation equipment and gas exhaust wind oxidation power generation equipment are connected to a 3300V AC bus; the energy storage system and DC load are connected to a 1500V DC bus; and the photovoltaic power generation system is connected to the 10kV DC bus through a DC-DC conversion module and switch S9.

2. The AC / DC hybrid intelligent power supply and distribution system for underground coal mines according to claim 1, characterized in that, The photovoltaic power generation system is a centralized photovoltaic power generation system.

3. The AC / DC hybrid intelligent power supply and distribution system for underground coal mines according to claim 1, characterized in that, It also includes transformer T4, through which the 3300V AC busbar is connected to the 1140V AC busbar, which is used to supply power to the equipment and electric auxiliary transport vehicles at the tunneling face.

4. The control method for an AC / DC hybrid intelligent power supply and distribution system in an underground coal mine according to claim 1, characterized in that, include: State (1): When both the ground four-port power electronic transformer U1 and the underground four-port power electronic transformer U2 are in normal working condition, switch S6 is disconnected and switches S1~S5 and S7~S8 are closed; the control strategies for each port of the ground four-port power electronic transformer U1 are as follows: the 10kV medium-voltage AC port implements the grid-connected following operation strategy, and the power of the mains network is determined by the sum of the power of the other ports, presenting an overall power balance of the four ports; the 3300V medium-voltage AC port implements voltage source control; the 1500V low-voltage DC port implements voltage source control; the 10kV medium-voltage DC port implements voltage source control to keep the voltage of the 10kV DC bus stable; The control strategies for each port of the underground four-port power electronic transformer U2 are as follows: the 10kV medium-voltage DC port adopts a droop control mode, which, together with the 10kV medium-voltage DC port of the surface four-port power electronic transformer U1, stabilizes the voltage and power balance of the 10kV DC bus; the 3300V medium-voltage AC port adopts a voltage source control mode, which supplies power to the coal mining face equipment connected to the 3300V AC bus, and after passing through a first-stage transformer to 1140V, supplies power to the tunneling face; the 1500V low-voltage DC port implements a voltage source control mode, which supplies power to the underground DC load; the 10kV medium-voltage AC port is in a locked state. The power generation devices connected to the 3300V AC bus operate under maximum power control and are connected to the 3300V AC bus. The ground and underground energy storage devices connected to the 1500V DC bus cooperate with the new energy output to perform peak shaving and valley filling, and the energy storage priority of underground energy storage is greater than that of ground energy storage. The photovoltaic power generation system connected to the 10kV DC bus operates under maximum power control, and the generated power is transmitted in the following order: underground load, underground energy storage, ground load, ground energy storage and connection to the municipal power grid. State (2): When both the surface four-port power electronic transformer U1 and the underground four-port power electronic transformer U2 are faulty, disconnect switches S1-S9 to lock each port of the two four-port power electronic transformers, close switch S14, and use the 10kV AC bus to supply power to the underground equipment. State (3): When the ground four-port power electronic transformer U1 fails and stops, and the underground four-port power electronic transformer U2 is working normally, disconnect switches S1~S4 and close switches S5~S9 to lock all ports of the ground four-port power electronic transformer U1. The control strategies for each port of the underground four-port power electronic transformer U2 are as follows: the 10kV medium-voltage AC port implements the grid-connected following operation strategy, and the power of the mains network depends on the power of the other ports, and the overall power balance of the four ports is presented; the 3300V medium-voltage AC port implements voltage source control, and the power is determined by the load; the 1500V low-voltage DC port implements voltage source control; the 10kV medium-voltage DC port adopts droop control of the 10kV DC bus voltage; the underground energy storage device performs emergency energy storage according to the charging and discharging strategy and charge and discharge management according to the peak and valley electricity price, and provides the other DC equipment for use after being stepped down by the DC / DC device; State (4): When the underground four-port power electronic transformer U2 fails and shuts down, and the surface four-port power electronic transformer U1 is working normally, close switches S1~S4 and S9, and open switches S5~S8 to lock all ports of the underground four-port power electronic transformer U2. The control strategies for each port of the surface four-port power electronic transformer U1 are as follows: the 10kV AC port implements the grid-connected follow-up operation strategy; the 3300V medium-voltage AC port implements voltage source control; the 1500V low-voltage DC port implements voltage source control; the 10kV medium-voltage DC port implements voltage source control to stabilize the voltage of the 10kV DC bus; the power generation device connected to the 3300V AC bus operates according to the maximum power generation control and is connected to the 3300V AC bus; the ground energy storage device connected to the 1500V DC bus cooperates with the new energy output to perform peak shaving and valley filling; the photovoltaic power generation system connected to the 10kV DC bus adopts the maximum power generation control operation.

5. The control method for an AC / DC hybrid intelligent power supply and distribution system in an underground coal mine according to claim 4, characterized in that, The intelligent power supply and distribution system also includes two independent 35kV power grid inputs. The first 35kV power grid input is connected to the 10kV AC bus via transformer T1 and switch S10. The second 35kV power grid input is connected to the backup 10kV AC bus via transformer T2 and switch S11. The 10kV AC bus and the backup 10kV AC bus are connected via switches S12 and S13. The control method also includes: When the 10kV AC busbar is normal, close switches S10 and S11 and open switches S12 and S13. When the 10kV AC bus fails, close switches S11, S12 and S13, open switch S10, switch to standby 10kV AC bus, and maintain the control strategy of the ground four-port power electronic transformer U1 and the underground four-port power electronic transformer U2 in the state (1).

6. The control method for an AC / DC hybrid intelligent power supply and distribution system in an underground coal mine according to claim 4, characterized in that, When the underground four-port power electronic transformer U2 malfunctions, switch S14 is closed; when the underground four-port power electronic transformer U2 is functioning normally, switch S14 is opened.

7. The control method for an AC / DC hybrid intelligent power supply and distribution system in an underground coal mine according to claim 4, characterized in that, When both the surface four-port power electronic transformer U1 and the underground four-port power electronic transformer U2 are in normal working condition, if a fault occurs in the 10kV DC bus transmission, switch S6 will be closed to enable the 10kV medium-voltage AC port of the underground four-port power electronic transformer U2 to supply power to the underground working face load.

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