Power grid loop closing device and power grid system

Abstract

The utility model relates to a power grid loop closing device and a power grid system, the power grid loop closing device comprises a multi-winding transformer, a winding adjusting unit and a loop closing conditioning transformer, the primary side of the multi-winding transformer is connected with a first power grid and a second power grid, the secondary side of the multi-winding transformer is connected with the winding adjusting unit, and the winding adjusting unit is connected with the primary side of the loop closing conditioning transformer. The secondary side of the loop closing conditioning transformer is connected with the first power grid and the second power grid. Wherein the winding adjusting unit is used for controlling the secondary side of the multi-winding transformer to output adjusting voltages with different amplitudes and phases, the primary side of the closed-loop conditioning transformer receives the adjusting voltages and outputs closed-loop voltages according to the adjusting voltages, and the closed-loop voltages are used for completing grid connection of a first power grid and a second power grid. The electric energy between the two power grids is conditioned through the power grid loop closing device, the current flow during loop closing of the power grids is reduced, and the stability of each power grid in the loop closing process is guaranteed.

Description

Technical Field

[0001] The present application relates to the technical field of power systems, and particularly to a power grid loop closing device and a power grid system. Background Art

[0002] As the basic bearing network of electric energy, the flexible adjustment performance of the distribution network directly determines the efficient power supply and reliable operation capabilities of the current active distribution network, and is also the operation foundation of the power system. Currently in the power system, corresponding distribution networks are established according to conditions such as usage areas or functions to respectively meet their design requirements.

[0003] With the rapid transformation of the energy supply structure, a larger scale of distributed generation and new loads will be connected to the distribution network. Under the traditional operation mode of "closed-loop design and open-loop operation", the original distribution network has problems such as insufficient line overload power supply capacity, resulting in low operation efficiency. Usually, it is considered to connect multiple distribution networks in parallel and close the loop to enable the flow of electric energy therein, so as to provide reliable power supply for different requirements of different distribution networks without reconstructing the distribution network.

[0004] However, there are voltages with different phases in different distribution networks, and their voltage amplitudes are also different. When different distribution networks are looped, problems such as uneven power flow will occur, resulting in difficulties in closing the loop and a decrease in power supply stability. Summary of the Utility Model

[0005] Based on this, in view of the above technical problems, it is necessary to provide a power grid loop closing device and a power grid system that can improve power supply stability.

[0006] In a first aspect, the present application provides a power grid loop closing device, including a multi-winding transformer, a winding adjustment unit, and a loop closing conditioning transformer. The primary side of the multi-winding transformer is connected to a first power grid and a second power grid, the secondary side of the multi-winding transformer is connected to the winding adjustment unit, the winding adjustment unit is connected to the primary side of the loop closing conditioning transformer, and the secondary side of the loop closing conditioning transformer is connected to the first power grid and the second power grid;

[0007] The winding adjustment unit is used to control the secondary side of the multi-winding transformer to output adjustment voltages with different amplitudes and phases. The primary side of the loop closing conditioning transformer receives the adjustment voltages and outputs loop closing voltages according to the adjustment voltages. The loop closing voltages are used to complete the parallel connection of the first power grid and the second power grid.

[0008] In one embodiment, the winding adjustment unit includes a plurality of switches, and each switch is respectively connected to different windings of the secondary side of the multi-winding transformer.

[0009] In one embodiment, the switch is a thyristor component.

[0010] In one embodiment, the grid closing device further includes a voltage protector, and the voltage protector is connected to the primary side of the closing regulating transformer and the winding regulating unit.

[0011] In one embodiment, the grid closing device further includes a first voltage protector and a second voltage protector. The first voltage protector is connected to the first power grid, the primary side of the multi-winding transformer, and the secondary side of the closing regulating transformer. The second voltage protector is connected to the second power grid and the secondary side of the closing regulating transformer.

[0012] In one embodiment, the grid closing device further includes a first circuit breaker and a second circuit breaker. The first circuit breaker is disposed between the first power grid and the primary side of the multi-winding transformer. The second circuit breaker is disposed between the second power grid and the primary side of the multi-winding transformer.

[0013] In one embodiment, the grid closing device further includes a short-circuit switch, and the short-circuit switch is connected to the first power grid and the second power grid.

[0014] In one embodiment, the grid closing device further includes a circuit detection unit, and the circuit detection unit is connected to the first power grid and the second power grid.

[0015] In one embodiment, the circuit detection unit is further disposed on the primary side of the multi-winding transformer and the primary side of the closing regulating transformer.

[0016] In a second aspect, the present application further provides a power grid system, which includes a first power grid, a second power grid, and the grid closing device as described above. The grid closing device is connected to the first power grid and the second power grid.

[0017] The above-mentioned grid closing device and power grid system include a multi-winding transformer, a winding regulating unit, and a closing regulating transformer. The primary side of the multi-winding transformer is connected to the first power grid and the second power grid. The secondary side of the multi-winding transformer is connected to the winding regulating unit. The winding regulating unit is connected to the primary side of the closing regulating transformer. The secondary side of the closing regulating transformer is connected to the first power grid and the second power grid. Among them, the winding regulating unit is used to control the secondary side of the multi-winding transformer to output regulating voltages with different amplitudes and phases. The primary side of the closing regulating transformer receives the regulating voltage and outputs a closing voltage according to the regulating voltage. The closing voltage is used to complete the grid connection of the first power grid and the second power grid. By conditioning the electric energy between the two power grids through the grid closing device, the current flow during grid closing is reduced, and the stability of each power grid during the closing process is ensured. Description of the Drawings

[0018] To more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the following will briefly introduce the accompanying drawings required for the description in the embodiments of the present application or related technologies. Obviously, the accompanying drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0019] Figure 1 It is an application environment diagram of a power grid closing device in an embodiment;

[0020] Figure 2 It is a schematic structural diagram of a power grid closing device in an embodiment;

[0021] Figure 3 It is a schematic structural diagram of a power grid closing device in another embodiment;

[0022] Figure 4 It is a schematic structural diagram of a power grid closing device in yet another embodiment.

[0023] Explanation of reference numerals: First power grid 101, power grid closing device 102, second power grid 103, multi-winding transformer 202, winding adjustment unit 204, closing conditioning transformer 206, voltage protection device 302. Detailed implementation manners

[0024] In order to make the purpose, technical solutions and advantages of the present application clearer, the following further details the present application in combination with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0025] It can be understood that the terms "first", "second", etc. used in the present application can be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish the first element from another element. For example, without departing from the scope of the present application, the first resistor can be called the second resistor, and similarly, the second resistor can be called the first resistor. Both the first resistor and the second resistor are resistors, but they are not the same resistor.

[0026] It can be understood that in the following embodiments, "connection", if there is an electrical signal or data transmission between the connected circuits, modules, units, etc., should be understood as "electrical connection", "communication connection", etc.

[0027] As used herein, the singular forms "a", "an" and "the" may also include the plural forms unless the context clearly dictates otherwise. It should also be understood that the terms "comprises / comprising", "has / including", etc. specify the presence of the stated features, integers, steps, operations, components, parts, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs. The terms used in the description of this application herein are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0029] In one embodiment, as Figure 1 and Figure 2 shown, this application provides a power grid closing device 102, including a multi-winding transformer 202, a winding adjustment unit 204 and a closing conditioning transformer 206. The primary side of the multi-winding transformer 202 is connected to a first power grid 101 and a second power grid 103. The secondary side of the multi-winding transformer 202 is connected to the winding adjustment unit 204. The winding adjustment unit 204 is connected to the primary side of the closing conditioning transformer 206. The secondary side of the closing conditioning transformer 206 is connected to the first power grid 101 and the second power grid 103.

[0030] Among them, the first power grid 101 and the second power grid 103 are different distribution grids and are also the two distribution grids that need to be closed in this embodiment. It should be noted that the power grid closing device 102 can connect two power grids and close the two power grids. When there are more than three power grids that need to be closed, the number of power grid closing devices 102 is also multiple, and both ends of each power grid closing device 102 are respectively connected to a power grid that needs to be closed. Exemplarily, when there are n power grids that need to be closed in sequence, the number of power grid closing devices 102 is n - 1, where n is a natural number not equal to 0.

[0031] The first power grid 101 includes a 10 kV bus and a 110 kV bus for power supply. When the line switch K1 is closed, the electric energy on the 110 kV bus can be transmitted to the 10 kV bus. There are multiple pole-mounted switches on the 10 kV bus, and each two pole-mounted switches are connected to a substation area load (1#) through a branch switch. Workers can control the power supply of multiple substation area loads connected in the first power grid 101 by controlling the conduction and disconnection of the pole-mounted switches and the branch switches. Further, the first power grid 101 also includes a tie switch K3, and the tie switch K3 is arranged at one end of the first power grid 101 far from the 110 kV bus and the tie switch K3 is closed when the first power grid 101 needs to be closed.

[0032] Similarly, the second power grid 103 also includes a 10 kV busbar and a 110 kV busbar for power supply. When the line switch K2 is closed, the electric energy on the 110 kV busbar can be transmitted to the 10 kV busbar. A plurality of pole-mounted switches are arranged on the 10 kV busbar, and a distribution transformer load (2#) is connected between every two pole-mounted switches through a branch switch. The staff can control the energization of a plurality of distribution transformer loads connected in the second power grid 103 by controlling the conduction and disconnection of the pole-mounted switches and the branch switches. Further, a tie switch K4 is also included in the second power grid 103. The tie switch K4 is arranged at one end of the second power grid 103 far from the 110 kV busbar and is closed when the second power grid 103 needs to be looped.

[0033] The power grid loop closing device 102 can be connected to the tie switch K3 and the tie switch K4, obtain the electric energy of the first power grid 101 through the tie switch K3, and obtain the electric energy of the second power grid 103 through the tie switch K4. The power grid loop closing device 102 can condition the electric energies of the two according to the electric energy of the first power grid 101 and the electric energy of the second power grid 103, and then complete the grid connection of the first power grid 101 and the second power grid 103.

[0034] Specifically, the loop closing regulating transformer 206 and the multi-winding transformer 202 are both transformers, and their rated parameters are not limited and can be determined according to the circuit parameters of the power grid to be looped. Optionally, the rated capacity of the loop closing regulating transformer 206 can be greater than that of the multi-winding transformer 202. The multi-winding transformer 202 has multiple sets of windings. The secondary sides formed by different windings and the primary side form different turns ratios, so that different windings on the secondary side can output different voltages. The combination of multiple step-down windings with different voltage levels can output a regulated voltage. The winding regulating unit 204 is connected to the secondary side of the multi-winding transformer 202, specifically connected to each winding on the secondary side of the multi-winding transformer 202, and controls the output of the winding. The winding regulating unit 204 controls the secondary side of the multi-winding transformer 202 to output regulating voltages with different amplitudes and phases. The output regulating voltages are transmitted to the primary side of the loop closing regulating transformer 206. The primary side of the loop closing regulating transformer 206 receives the regulating voltages and outputs a loop closing voltage on the secondary side of the loop closing regulating transformer 206 according to transformer parameters such as the turns ratio between the primary side and the secondary side of the loop closing regulating transformer 206 itself. The loop closing voltage is used to complete the grid connection of the first power grid 101 and the second power grid 103. Since the secondary side of the loop closing regulating transformer 206 is connected to the first power grid 101 and the second power grid 103, the loop closing voltage output by the loop closing regulating transformer 206 can condition the electric energies of the first power grid 101 and the second power grid 103. Through the conditioning of the loop closing voltage, the current flow during the loop closing of the first power grid 101 and the second power grid 103 is reduced.

[0035] In this embodiment, it includes a multi-winding transformer 202, a winding regulation unit 204, and a closed-loop conditioning transformer 206. The primary side of the multi-winding transformer 202 is connected to a first power grid 101 and a second power grid 103. The secondary side of the multi-winding transformer 202 is connected to the winding regulation unit 204. The winding regulation unit 204 is connected to the primary side of the closed-loop conditioning transformer 206. The secondary side of the closed-loop conditioning transformer 206 is connected to the first power grid 101 and the second power grid 103. Among them, the winding regulation unit 204 is used to control the secondary side of the multi-winding transformer 202 to output regulated voltages with different amplitudes and phases. The primary side of the closed-loop conditioning transformer 206 receives the regulated voltage and outputs a closed-loop voltage according to the regulated voltage. The closed-loop voltage is used to complete the grid connection of the first power grid 101 and the second power grid 103. The power between the two power grids is conditioned through the power grid closed-loop device 102 to reduce the current flow during the power grid closed-loop and ensure the stability of each power grid during the closed-loop process.

[0036] In one embodiment, the winding regulation unit 204 includes a plurality of switches, and each switch is respectively connected to different windings on the secondary side of the multi-winding transformer 202.

[0037] Specifically, the switch has the function of controlling the on / off of the circuit. The winding regulation unit 204 includes a plurality of switches, and each switch is respectively connected to different windings on the secondary side of the multi-winding transformer 202, and can independently control the on / off of each winding. That is to say, when the switch connected to a certain winding is turned off, that winding is equivalent to an open circuit and the output voltage is zero; when the switch connected to a certain winding is turned on, that winding forms a loop and can output voltage. The multiple switching tubes respectively control the on / off of each winding and control the voltage output by each winding. The output voltage vectors of the multiple windings in the multi-winding transformer 202 are superimposed to obtain regulated voltages with different amplitudes and phases output by the secondary side of the multi-winding transformer 202.

[0038] The device for realizing the function of controlling the on / off of the circuit is not unique. In one embodiment, the switch is a thyristor component. Optionally, the thyristor component can include thyristors connected in parallel with reverse settings, or can include a plurality of bidirectional thyristors, and can perform split-phase regulation and recombination on the local windings of the multi-winding transformer 202 to synthesize voltages with different phases and amplitudes.

[0039] Thyristors have bidirectional conductivity, that is, they can conduct current under both forward and reverse voltages. This enables thyristors to be used in AC and DC circuits to achieve the control of bidirectional current. The switching characteristics of thyristors allow them to switch from the off state to the on state under the action of a control voltage. Once a thyristor is turned on, it will remain in the on state until the current drops to zero or is disconnected through external control. This switching characteristic enables thyristors to achieve efficient current switching control in a circuit. The on state of a thyristor can be controlled by a trigger current. When a sufficient current is applied to the gate of the thyristor, the thyristor can be controlled to switch from the off state to the on state. Therefore, by selecting thyristor components for the switcher, precise and convenient control can be achieved, thereby improving the accuracy of the obtained regulated voltage and further maintaining the stability of the closed loop.

[0040] Exemplarily, as Figure 3 shown, there are multiple windings on the secondary side of the multi-winding transformer 202, and each wire connection led out from a winding is connected to a corresponding thyristor component (the connection relationship of each thyristor component is omitted in the figure). The thyristor components are connected to the primary side of the closed-loop conditioning transformer 206. By controlling the windings to output different voltages, and the voltages output by multiple windings are superimposed to obtain the regulated voltage. Exemplarily, when the thyristor component connected to the winding where U 11 is located is turned on, the output regulated voltage is U 11 . When the thyristor components connected to the windings where U 11 , U 21 , U 31 , … U N1 are located are turned on, the output regulated voltage is the vector sum of U 11 , U 21 , U 31 , … U N1 .

[0041] In one embodiment, the power grid closed-loop device 102 further includes a voltage transformer protector 302, and the voltage transformer protector 302 is connected to the primary side of the closed-loop conditioning transformer 206 and the winding adjustment unit 204.

[0042] Specifically, the voltage transformer protector 302 can be a current-limiting reactor, which is a reactor commonly used to limit fault current and is used to ensure the stability of the operation of electrical equipment. In this embodiment, one end of the voltage transformer protector 302 is connected to the primary side of the closed-loop conditioning transformer 206 and the winding adjustment unit 204, and the other end of the voltage transformer protector 302 is connected to the primary side of the closed-loop conditioning transformer 206 and the winding adjustment unit 204 through a bypass switch BK3. When the bypass switch BK3 is closed, it is equivalent to short-circuiting the winding adjustment unit 204 and the multi-winding transformer 202. The primary side of the closed-loop conditioning transformer 206 is connected to the voltage transformer protector 302, and the closed-loop voltage output is stopped.

[0043] Optionally, when the grid closing device 102 fails or the working state of the grid closing device 102 needs to be switched, the staff can close the bypass switch BK3, and then adjust the working state of the closing regulating transformer 206. For example, when a power outage occurs in one of the first power grid 101 or the second power grid 103, and it is necessary to directly connect the other power grid to the power-out grid, at this time, the grid closing device 102 needs to stop working first and then connect the two power grids. Otherwise, a loop will be formed in the grid closing device 102, generating a large circulating current, which will affect the closing regulating transformer 206. At this time, the bypass switch BK3 can be provided first to put the voltage protector 302 into use, and then the two power grids can be connected. In this way, the components in the grid closing device 102 are not easily damaged and have a better service life.

[0044] The grid closing device 102 can be directly connected to the first power grid 101 and the second power grid 103, or can be connected through switches. In one embodiment, the grid closing device 102 further includes a first loop switch and a second loop switch. The first loop switch is disposed between the first power grid 101 and the primary side of the multi-winding transformer 202, and the second loop switch is disposed between the second power grid 103 and the primary side of the multi-winding transformer 202.

[0045] Specifically, the staff can control the connection between the grid closing device 102 and the first power grid 101 by controlling the first loop switch, or can control the connection between the grid closing device 102 and the second power grid 103 by controlling the second loop switch. As Figure 4 shown, the first loop switch is the access switch BK1, the second loop switch is the access switch BK2. The first loop switch is connected to the first power grid 101 and can control whether the first power grid 101 is connected to the grid closing device 102; the second loop switch is connected to the second power grid 103 and can control whether the second power grid 103 is connected to the grid closing device 102.

[0046] Optionally, when the first power grid 101 and the second power grid 103 need to be interconnected, the first loop switch can be closed first, and the grid closing device 102 obtains the voltage of the first power grid 101. Or the second loop switch can be closed first, and the grid closing device 102 obtains the voltage of the second power grid 103. Or the first loop switch and the second loop switch can be closed simultaneously.

[0047] Furthermore, in order to more conveniently complete the direct connection between the first power grid 101 and the second power grid 103 to cope with the situation of a single power grid power outage, in one embodiment, the grid closing device 102 further includes a short-circuit switch, and the bypass switch is connected to the first power grid 101 and the second power grid 103. As Figure 4As shown, the short - circuit switch is the bypass switch BK0. When the short - circuit switch is closed, the first power grid 101 is directly connected to the second power grid 103, and power can be supplied to the power grid that has lost power in the event of a power outage in one of the power grids.

[0048] In one embodiment, the power - grid closing - loop device 102 further includes a first voltage protector and a second voltage protector. The first voltage protector is connected to the first power grid 101, the primary side of the multi - winding transformer 202, and the secondary side of the closing - loop conditioning transformer 206. The second voltage protector is connected to the second power grid 103 and the secondary side of the closing - loop conditioning transformer 206.

[0049] Specifically, the first voltage protector and the second voltage protector can be earthing switches, lightning arresters, over - voltage absorbers, or can include one or more of the above - mentioned types of devices. When both the first voltage protector and the second voltage protector are earthing switches, they can be closed when the power - grid closing - loop device 102 is taken out of service or starts maintenance to protect the power - grid closing - loop device 102. When both the first voltage protector and the second voltage protector are disconnectors, they can be disconnected when the power - grid closing - loop device 102 is taken out of service or starts maintenance. When both the first voltage protector and the second voltage protector are lightning arresters or over - voltage absorbers, they can absorb abnormal voltages when detecting abnormal conditions such as excessive current or voltage in the first power grid 101 or the second power grid 103.

[0050] Exemplarily, as Figure 4 shown, the first voltage protector includes an earthing switch QS1 and a lightning arrester F1. The earthing switch QS1 and the lightning arrester F1 are connected in parallel. The first end after parallel connection is grounded, and the other end after parallel connection is connected to the first power grid 101, the primary side of the multi - winding transformer 202, and the secondary side of the closing - loop conditioning transformer 206. The second voltage protector includes an earthing switch QS2 and a lightning arrester F2. The earthing switch QS2 and the lightning arrester F2 are connected in parallel. The first end after parallel connection is grounded, and the other end after parallel connection is connected to the second power grid 103 and the secondary side of the closing - loop conditioning transformer 206.

[0051] In order to more accurately detect the working states of the first power grid 101, the second power grid 103, and the power - grid closing - loop device 102, in one embodiment, the power - grid closing - loop device 102 further includes a circuit detection unit, and the circuit detection unit is connected to the first power grid 101 and the second power grid 103.

[0052] Specifically, the circuit detection unit can detect circuit parameters in the circuit, including but not limited to circuit parameters such as current and voltage. The circuit detection unit is connected to the first power grid 101 to detect the circuit parameters of the first power grid 101; the circuit detection unit is connected to the second power grid 103 to detect the circuit parameters of the second power grid 103. Optionally, the circuit detection unit includes more than two current sensors and more than two voltage sensors. One current sensor and one voltage sensor are both connected to the first power grid 101 to detect the current and voltage of the first power grid 101; another current sensor and another voltage sensor are both connected to the second power grid 103 to detect the current and voltage of the second power grid 103.

[0053] Furthermore, in one embodiment, the circuit detection unit is also disposed on the primary side of the multi-winding transformer 202 and the primary side of the closed-loop conditioning transformer 206. The circuit detection unit disposed on the primary side of the multi-winding transformer 202 is used to detect the working state of the multi-winding transformer 202. The circuit detection unit disposed on the primary side of the closed-loop conditioning transformer 206 is used to detect the regulated voltage output by the winding regulating unit 204, can detect the working state of the winding regulating unit 204, and can also detect the working state of the closed-loop conditioning transformer 206 in combination with the circuit detection units disposed at other positions.

[0054] As Figure 4 shown, the circuit detection unit includes a low-voltage current transformer CT1, a low-voltage current transformer CT2, a protection current transformer CT3, a protection current transformer CT4, a voltage transformer TV1, a voltage transformer TV2, and a voltage transformer TV3. Among them, the low-voltage current transformer CT1 is used to detect the current parameters of the first power grid 101, the voltage transformer TV1 is used to detect the voltage parameters of the first power grid 101, the low-voltage current transformer CT2 is used to detect the current parameters of the second power grid 103, the voltage transformer TV2 is used to detect the voltage parameters of the second power grid 103, the protection current transformer CT3 is used to monitor the current on the primary side of the multi-winding transformer 202 during the use of the power grid closing device 102, the protection current transformer CT4 is used to monitor the current on the secondary side of the closed-loop conditioning transformer 206 during the use of the power grid closing device 102, and the voltage transformer TV3 is used to detect the regulated voltage to facilitate the protection of the power grid closing device 102.

[0055] Based on the same technical concept, the present application also provides a power grid system, as Figure 1 shown, the power grid system includes a first power grid 101, a second power grid 103, and a power grid closing device 102 as described in the above embodiments. The power grid closing device 102 is connected to the first power grid 101 and the second power grid 103.

[0056] To better understand the above solution, in combination with Figure 1For the application scenarios shown below, a specific embodiment will be used for detailed explanation.

[0057] As the role of the distribution network as the basic carrier network of electric energy is strengthened again, its flexible regulation performance directly determines whether the current active distribution network can supply power efficiently and operate reliably. In cities, the research on the operation mode of the distribution network plays an important fundamental supporting role in constructing the power system. To meet the requirements of the safe operation of the distribution network, regular maintenance of line equipment, accident handling, and overload load transfer, etc., it poses a huge challenge to the flexibility of the distribution network. Currently, in the power system, corresponding distribution networks are established according to conditions such as usage areas or functions to complete their respective design requirements. However, due to reasons such as cost and technology, for a long time, China's distribution network has mainly adopted the mode of "closed-loop design and open-loop operation", and this design architecture can no longer meet the increasingly urgent actual needs of the distribution network.

[0058] With the rapid transformation of the energy supply structure, a larger scale of distributed generation and new loads will be connected to the distribution network. Under the traditional operation mode, the original distribution network has problems such as insufficient line overload power supply capacity, which exacerbates problems such as low line overload power supply capacity, uneven power flow, low operation efficiency, low power supply reliability, and difficulty in closing the line loop. Therefore, realizing the closed-loop operation of the distribution network is considered an effective means to solve the above problems, that is, to connect multiple distribution networks in parallel and close the loop to enable the flow of electric energy, so as to provide reliable power supply for different needs of different distribution networks without reconstructing the distribution network.

[0059] Currently, the distribution network closed-loop technologies adopted generally include the following:

[0060] 1) Automated assisted closed-loop technology. The automated assisted closed-loop technology that calculates the closed-loop power flow through an automated system to provide assisted closed-loop decision-making still cannot achieve closed-loop power transfer when the closed-loop conditions are not met. 2) Double-petal closed-loop operation technology. The double-petal closed-loop operation technology achieved by re-planning and constructing a new grid framework has problems such as large construction investment and low line utilization rate, and it also cannot achieve power flow regulation. 3) Flexible closed-loop technology. The flexible closed-loop technology can not only achieve closed-loop power transfer but also achieve power flow regulation, and can ensure the stability of the closed-loop between power grids. Therefore, it has also become an important direction for the development of technology in the field of power grid closed-loop.

[0061] The "back-to-back" AC-DC-AC flexible loop closing technology solution, which is usually based on high-power power electronic devices, adopts the AC-DC-AC method and adjusts the amplitude and phase of the power output from the sending end to the receiving end through the control loop. Its advantage is that the output can be adjusted to any phase and voltage. However, due to the large power required for loop closing transfer and limitations such as technology and manufacturing costs, there are problems in the AC-DC-AC flexible loop closing technology solution, such as high cost, large volume, high loss, difficult maintenance, and low reliability, making it difficult to be widely promoted and used in the distribution network.

[0062] Therefore, considering the large number of distribution network points and the wide area, and the large demand for loop closing in the distribution network, there is an urgent need for a grid loop closing device that can achieve flexible loop closing to maintain power supply stability during the loop closing process.

[0063] In one embodiment, the grid loop closing device is as Figure 4 shown, and the specific functions of each component are as follows:

[0064] 1) QS1 and QS2 are disconnectors and earthing switches, which are used for the input / removal of the grid loop closing device. When the grid loop closing device exits operation and transfers to maintenance, the disconnector is opened and the earthing switch is closed.

[0065] 2) F1 and F2 are lightning arresters, which are used to absorb overvoltage on the grid connection lines of the two power grids and prevent lightning overvoltage.

[0066] 3) The multi-winding transformer 202 is a parallel multi-winding phase-shifting transformer (TS1), and its multiple step-down windings with different voltage levels are used to combine and generate the voltage required by the flexible interconnection device.

[0067] 4) The loop closing conditioning transformer 206 is a series coupling transformer (TS2), which is used for coupling on the grid connection lines of the two power grids by the grid loop closing device and inserting a compensation voltage according to the regulated voltage.

[0068] 5) The winding adjustment unit is a thyristor module (SCR), which is composed of multiple bidirectional thyristors and is used for phase-by-phase adjustment and recombination of multiple low-voltage local windings of the parallel multi-winding phase-shifting transformer, synthesizing voltages with different phases and amplitudes, and controlling the output regulated voltage of the parallel multi-winding phase-shifting transformer.

[0069] 6) L is a current-limiting reactor (voltage transformer protector 302), which is used for suppressing circulating current during the working state switching process of the grid loop closing device and protecting the series coupling transformer.

[0070] 7) BK0 is a bypass switch (short-circuit switch), which is used to close when the grid loop closing device exits operation.

[0071] 8) The first loop switch is the access switch BK1, and the second loop switch is the access switch BK2, which are used to control the grid closing operation of the power supply lines on both sides of the grid.

[0072] 7) The bypass switch BK3 is the bypass circuit breaker of the current limiting reactor, which is used for the input and withdrawal of the current limiting reactor.

[0073] 9) CT1 and CT2 are low-voltage current transformers, which are used to measure the currents of the lines on both sides of the grid.

[0074] 10) CT3 and CT4 are current transformers for protection, which are used for current detection during switching.

[0075] 11) TV1 and TV2 are voltage transformers, which are used for voltage detection of the feeders at both ends.

[0076] 12) TV3 is a voltage transformer, which is used for voltage detection of the regulated voltage obtained after the combination of multiple windings of the parallel multiple-winding phase-shifting transformer and for system protection.

[0077] During the actual working process of the grid closing device, the work can be divided into three modes:

[0078] 1) Closing operation mode

[0079] When the grid closing device performs the closing operation, the bypass switch BK0 is disconnected by switching. The voltage amplitudes and phases of the first grid 101 and the second grid 102 before closing the access switches BK1 and BK2 are detected by the low-voltage current transformer CT1 and the voltage transformer TV1, and the amplitude and phase of the regulated voltage are obtained. The transistor module in the grid closing device adjusts the switching states of each thyristor, selects the combination mode of the multiple-winding phase-shifting transformer, and generates a voltage close to the voltage difference at both ends, that is, the regulated voltage. The regulated voltage is transmitted to the primary side of the series coupling transformer and is coupled in series to the line where the grid is connected through the series coupling transformer. In this way, when closing the access switches (BK1 and BK2) for the closing operation, the circulating current in the 10 kV line at the moment of closing can be greatly improved, and the closing operation will not cause a serious line overcurrent phenomenon. The line switches K1, the line switch K2, and the switches of the main line will not trip due to the overcurrent caused by the closing, ensuring the smooth completion of the closing operation.

[0080] 2) Power flow regulation mode

[0081] After the successful closed-loop operation, that is, after the access switches (BK1 and BK2) are closed, the power grid closed-loop device can adjust the power flow of the power grid lines at both ends according to the instructions issued by the remote dispatch, that is, transfer the electric energy in the power grid, and make adaptive adjustments according to the electric energy and load conditions of the first power grid 101 and the second power grid 103. Specifically, it can control the thyristor module to adjust the working state of the thyristors, and then adjust the winding output combination of the parallel multi-winding phase-shifting transformer to generate an adjustable regulating voltage with an adjustable amplitude and phase required for the power supply of the power grid line after grid connection. Then, it is coupled to the power grid line after grid connection through the series coupling transformer for power flow regulation, and on the basis of not powering off, realizes the transfer power supply after the grid connection of the power grids at both ends.

[0082] 3) Power flow transfer mode

[0083] At this time, one power grid loses power, and the other power grid needs to directly supply power to the power grid that has lost power. When switching from the closed-loop operation mode to the power flow transfer mode, switch disconnection and connection operations need to be performed. After the bypass switch BK0 is closed, the access switches (BK1 and BK2) and the current-limiting reactor L will form a loop, and a large circulating current will be generated during the process, which will affect the series coupling transformer TS2. Therefore, it is necessary to first put the current-limiting reactor into operation through the bypass switch BK3 and then close the bypass switch BK0. The specific steps are as follows: first lock all the thyristor valves in the thyristor module, then close the bypass switch BK3 to incorporate the current-limiting reactor L into the system, and then close the bypass switch BK0. Finally, perform a disconnection operation on the access switches (BK1 and BK2) to withdraw the power grid closed-loop device from operation, so that the power flow in the power grid lines on both sides is transferred through the bypass switch BK0, thus realizing the rapid transfer of the load.

[0084] In this embodiment, the power grid closed-loop device and the power system adopt the idea of a power electronic technology hybrid transformer to construct an innovative voltage regulating and phase adjusting equipment to realize the flexible closed-loop of the line. Through the semi-controlled thyristor module, the local windings of the multi-winding phase-shifting transformer are phase-adjusted and reorganized, so that the passive transformer components show the effect of active controllability, indirectly realizing the active adjustment of voltage and phase, and making the closed-loop line meet the requirements of the closed-loop transfer power supply conditions. When ensuring the effective and reliable closed-loop operation of the lines at the same voltage level in the distribution network, it will not cause the failure of the closed-loop operation due to overcurrent, greatly enhancing the power supply reliability of the distribution network, and enabling the distribution network to have the functions of long-term closed-loop and power flow regulation.

[0085] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combinations of these technical features do not conflict, they should all be considered to be within the scope recorded in this application.

[0086] The above-described embodiments merely represent several implementation manners of the present application. The description thereof is relatively specific and detailed, but it should not be construed as a limitation to the patent scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all fall within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the appended claims.

Claims

1. A power grid loop closing device, characterized in that, It includes a multi-winding transformer, a winding regulating unit and a closed-loop conditioning transformer. The primary side of the multi-winding transformer is connected to a first power grid and a second power grid. The secondary side of the multi-winding transformer is connected to the winding regulating unit. The winding regulating unit is connected to the primary side of the closed-loop conditioning transformer. The secondary side of the closed-loop conditioning transformer is connected to the first power grid and the second power grid; The winding regulating unit is used to control the secondary side of the multi-winding transformer to output regulating voltages with different amplitudes and phases. The primary side of the closed-loop conditioning transformer receives the regulating voltage and outputs a closed-loop voltage according to the regulating voltage. The closed-loop voltage is used to complete grid connection of the first power grid and the second power grid.

2. The power grid loop closing device according to claim 1, characterized in that The winding regulating unit includes a plurality of switches, and each of the switches is respectively connected to different windings of the secondary side of the multi-winding transformer.

3. The power grid loop closing device according to claim 2, wherein The switch is a thyristor component.

4. The power grid loop closing device according to claim 1, characterized in that The grid closed-loop device further includes a voltage protector, and the voltage protector is connected to the primary side of the closed-loop conditioning transformer and the winding regulating unit.

5. The power grid closing loop device according to claim 1, wherein The grid closed-loop device further includes a first voltage protector and a second voltage protector. The first voltage protector is connected to the first power grid, the primary side of the multi-winding transformer and the secondary side of the closed-loop conditioning transformer. The second voltage protector is connected to the second power grid and the secondary side of the closed-loop conditioning transformer.

6. The power grid loop closing device according to claim 1, wherein The grid closed-loop device further includes a first circuit switch and a second circuit switch. The first circuit switch is arranged between the first power grid and the primary side of the multi-winding transformer. The second circuit switch is arranged between the second power grid and the primary side of the multi-winding transformer.

7. The power grid loop closing device according to claim 1, wherein The grid closed-loop device further includes a short-circuit switch, and the short-circuit switch is connected to the first power grid and the second power grid.

8. The power grid loop closing device according to claim 1, characterized in that The grid closed-loop device further includes a circuit detection unit, and the circuit detection unit is connected to the first power grid and the second power grid.

9. The power grid loop closing device according to claim 8, wherein The circuit detection unit is further arranged at the primary side of the multi-winding transformer and the primary side of the closed-loop conditioning transformer.

10. A power grid system, characterized in that, The power grid system includes a first power grid, a second power grid and the grid closed-loop device according to any one of claims 1-9. The grid closed-loop device is connected to the first power grid and the second power grid.

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