A power distribution network non-power-off loop closing power supply device and control method

Abstract

The application provides a power distribution network non-stop loop transfer device and a control method. The device comprises a loop transfer controller, a DC voltage stabilizing circuit, a series compensation circuit and a load switching circuit connected in sequence. The DC voltage stabilizing circuit is used as the DC input of the series compensation circuit to provide voltage support. The series compensation circuit is connected between the original supply bus and the transfer bus when working to compensate the voltage difference between the original supply bus and the transfer bus. The load switching circuit is used to control the connection and disconnection of the series compensation circuit between the original supply bus and the transfer bus. The loop transfer controller is used to collect signals of the original supply bus, the transfer bus, the DC voltage stabilizing circuit and the series compensation circuit, and control the loop transfer device to complete the loop transfer between the original supply bus and the transfer bus. In the application, the series compensation circuit does not need to bear all the loads on the original supply bus, and only needs to be designed according to the power required to generate the compensation voltage, thereby reducing the required power electronic converter capacity.

Description

Technical Field

[0001] This invention relates to the field of power distribution network operation technology, specifically to a power distribution network uninterrupted loop transfer device and control method. Background Technology

[0002] In my country, the 110kV and below power grid typically uses an open-loop radial power supply configuration. When the power supply to the distribution network needs to be adjusted due to fault repair or planned maintenance, a short-term closed-loop reversal is usually employed to avoid affecting user power supply. However, due to factors such as uneven load flow between different power supply areas (inconsistent equivalent impedance), different main transformer winding connection methods (Δ connection, Y connection), and power supply originating from different 220kV lines, there may be a significant phase angle difference between the voltage phasors on both sides of the closed-loop point. Direct closed-loop operation under a high phase angle difference may generate a large closed-loop inrush current, potentially causing serious consequences such as protection tripping, distribution network line disconnection, and equipment burnout, and must be restricted.

[0003] Chinese Patent CN112803407B discloses a seamless loop-connection method and system for low-voltage distribution networks based on a parallel converter. The principle is as follows: First, a parallel converter is used to achieve flexible interconnection between the original supply bus and the transfer bus. Then, the output power of the parallel converter is adjusted so that the output power of the original supply bus is zero. Next, the power supply to the original supply bus is cut off, and the load on the original supply bus is supplied by the transfer bus via the parallel converter. Then, the voltage of the parallel converter is adjusted so that the voltage vector difference between the transfer bus and the original supply bus is within the loop-connection range. Then, the switch between the transfer bus and the original supply bus is closed. Since the voltage difference is now controlled within the loop-connection range, the inrush current is very low. Finally, the parallel converter is deactivated, achieving uninterrupted loop-connection. However, this scheme requires the parallel converter to bear the entire load on the original supply bus for a relatively long time, necessitating a large-capacity power electronic converter, resulting in problems such as large size, high cost, and complex control.

[0004] Chinese patent application CN119695866A discloses a method, system, equipment, and storage medium for uninterrupted load transfer control in a distribution network based on series compensation. This scheme differs from Chinese patent CN112803407B in that it utilizes a series compensation voltage source to achieve flexible interconnection between the original power supply bus and the transfer bus. After the full load transfer is achieved via the series compensation voltage source, the series compensation voltage is adjusted to the allowable range for loop closure, the switch between the transfer bus and the original power supply bus is closed, and the series compensation voltage source is deactivated. Although this scheme requires less equipment capacity than a parallel converter, the entire load on the original power supply bus still flows through the branch containing the series compensation voltage source for a considerable period, resulting in a relatively large required equipment capacity and higher cost and size.

[0005] In summary, there is an urgent need for a power distribution network uninterrupted loop transfer device and control method to solve the problems existing in the current technology. Summary of the Invention

[0006] The purpose of this invention is to provide a live-line switching device for power distribution networks, aiming to solve the problems of existing technologies where power electronic equipment needs to bear the entire load of the original power bus for a long time during the switching process, requiring large-capacity power electronic equipment, resulting in large size, high cost, and complex control. The specific technical solution is as follows:

[0007] A power distribution network uninterruptible loop switching device includes a loop switching controller and a DC voltage regulator circuit, a series compensation circuit and a load switching circuit connected in sequence.

[0008] The DC voltage regulator circuit serves as the DC input of the series compensation circuit, providing voltage support.

[0009] The series compensation circuit is connected in series between the original power supply bus and the transfer power supply bus during operation to compensate for the voltage difference between the original power supply bus and the transfer power supply bus.

[0010] The load switching circuit is used to control the connection and disconnection of the series compensation circuit between the original power supply bus and the transfer power supply bus;

[0011] The loop-connection and transfer controller is used to acquire signals from the original supply bus at the loop-connection point, the transfer bus at the loop-connection point, the DC voltage regulator circuit, and the series compensation circuit, and to control the loop-connection and transfer device to complete the loop-connection and transfer between the original supply bus and the transfer bus.

[0012] Preferably, the series compensation circuit includes a series compensation transformer, a three-phase inverter, and a fast bypass circuit. The positive and negative input terminals of the three-phase inverter are connected to the positive and negative output terminals of the DC voltage regulator circuit via a DC bus. The three output phases of the three-phase inverter are connected to the three phases of the primary winding of the series compensation transformer. The three phases of the secondary winding of the series compensation transformer are connected to or disconnected between the primary power supply bus and the transfer power supply bus via a load switching circuit. Each of the three output phases of the three-phase inverter is equipped with a fast bypass circuit. When the fast bypass circuit is turned on, it bypasses the corresponding phase of the primary winding of the series compensation transformer.

[0013] Preferably, the three-phase inverter includes a three-phase full-bridge circuit and a current-limiting inductor. The positive and negative input terminals of the three-phase full-bridge circuit are connected to the positive and negative output terminals of the DC voltage regulator circuit via a DC bus. The three output phases of the three-phase full-bridge circuit are connected in series with corresponding current-limiting inductors and then connected to the three phases of the primary winding of the series compensation transformer. The fast bypass circuit is connected to the output terminal of the current-limiting inductor of the corresponding phase.

[0014] Preferably, the DC voltage regulator circuit includes an energy storage battery, a DC voltage regulator converter, and a DC voltage regulator capacitor. The positive and negative input terminals of the DC voltage regulator converter are connected to the positive and negative terminals of the energy storage battery, respectively. The positive and negative output terminals of the DC voltage regulator converter are connected to the positive and negative input terminals of the three-phase inverter via a DC bus. The DC voltage regulator capacitor is connected in series between the positive and negative output terminals of the DC voltage regulator converter.

[0015] Preferably, if the output voltage of the energy storage battery is higher than the rated voltage of the DC bus, the DC-DC converter adopts a buck DC-DC regulator circuit; if the output voltage of the energy storage battery is lower than the rated voltage of the DC bus, the DC-DC converter adopts a boost DC-DC regulator circuit.

[0016] Preferably, the fast bypass circuit includes a first anti-parallel thyristor group and a buffer reactor connected in series. The input terminal of the first anti-parallel thyristor group is connected to the output terminal of the corresponding current-limiting inductor, and the output terminal of the buffer reactor is connected to the neutral point of the three phases of the primary winding of the series compensation transformer.

[0017] Preferably, each phase of the load switching circuit includes a second anti-parallel thyristor group, a first AC circuit breaker, and a second AC circuit breaker. One end of the secondary winding of each phase of the series compensation transformer is connected to the original power supply bus on one side of the tie switch at the closing point through the first AC circuit breaker of the corresponding phase. The other end of the secondary winding of each phase is connected to the transfer power supply bus on the other side of the tie switch at the closing point through the second AC circuit breaker of the corresponding phase. The two ends of the second anti-parallel thyristor group are respectively connected to the two ends of the secondary winding of the corresponding phase.

[0018] Preferably, both the first anti-parallel thyristor group and the second anti-parallel thyristor group include two thyristors connected in parallel and the conduction directions of the two thyristors are opposite.

[0019] Preferably, the loop-connected power transfer controller includes a sampling circuit and a microcontroller unit. The sampling circuit is used to collect the three-phase voltage of the original power supply bus, the three-phase voltage of the transfer power supply bus, the loop-connected three-phase current at the loop-connection point, the three-phase current output by the three-phase inverter, the three-phase voltage output by the three-phase inverter, the DC bus output voltage, and the DC bus output current. The microcontroller unit sends control signals to the DC-DC converter, the three-phase inverter, the fast bypass circuit, and the load switching circuit based on the signals collected by the sampling circuit to complete the loop-connected power transfer.

[0020] The present invention also provides a control method for the aforementioned uninterruptible power supply loop transfer device in the power distribution network, comprising:

[0021] After connecting the loop transfer device in parallel to both ends of the tie switch at the loop point, close the first AC circuit breaker on the side of the original supply bus in the load switching circuit, and collect the three-phase voltage of the original supply bus, the three-phase voltage of the transfer bus, the loop three-phase current at the loop point, the three-phase current output by the three-phase inverter, the three-phase voltage output by the three-phase inverter, the DC bus output voltage, and the DC bus output current.

[0022] Based on the DC output voltage and the DC bus output current, the DC voltage regulator circuit performs closed-loop control of the output voltage to adjust the DC bus voltage to the rated voltage.

[0023] Divide the three-phase voltage difference between the original supply bus and the transfer supply bus by the turns ratio of the series compensation transformer, and adjust the three-phase voltage output of the three-phase inverter according to the calculation results so that the output voltage of the secondary winding of the series compensation transformer can compensate for the voltage difference between the original supply bus and the transfer supply bus.

[0024] Close the second AC circuit breaker on the side of the transfer bus in the load switching circuit so that the series compensation circuit can be connected between the original supply bus and the transfer bus to compensate for the voltage difference.

[0025] Once the three-phase inverter output stabilizes, the power supply to the original supply bus is disconnected, and the load on the original supply bus is transferred to the transfer bus via the loop transfer device, causing a surge in the output current of the three-phase inverter.

[0026] When the current of any one phase of the three-phase inverter output exceeds the set current threshold At this time, the first anti-parallel thyristor group in the control fast bypass circuit is turned on, and the drive pulse of the three-phase inverter is blocked, so that the load current is transferred to the fast bypass circuit; at this time, the output current of the three-phase inverter decreases, and the voltage at the input and output terminals of the series compensation transformer begins to oscillate. During the oscillation, the voltage of the original power supply bus decreases.

[0027] When the voltage difference between the original supply bus and the transfer bus is less than the preset closed-loop operating voltage difference, the second anti-parallel thyristor group of the load switching circuit is turned on.

[0028] After a delay of time T, the connecting switch is closed, the first AC circuit breaker and the second AC circuit breaker are disconnected, the loop transfer device is taken out of operation, and the uninterrupted loop transfer is completed.

[0029] Furthermore, when adjusting the three-phase voltage output of the three-phase inverter based on the calculation results, a three-phase inverter voltage command is generated based on the calculation results. When the phase deviation of the series compensation transformer exceeds the threshold, phase compensation is performed on the value in the three-phase inverter voltage command based on the value of the phase deviation. Then, the three-phase inverter is subjected to voltage and current dual closed-loop control so that the three-phase voltage output by the three-phase inverter is the same as the value in the three-phase inverter voltage command.

[0030] The application of the technical solution of the present invention has the following beneficial effects:

[0031] This invention utilizes a fast bypass circuit in a series compensation circuit. The working principle is as follows: Initially, the loop-closing device closes the loop, and the series compensation device only compensates for the voltage phase difference between the two sides, with a very small current. Then, one side's switch is opened, and the load current shifts from the original power supply side to the transferred power supply side. The current in the series compensation device increases, and after reaching a certain threshold, the fast bypass circuit activates, bypassing the series compensation circuit so that it does not bear the entire load current from the original power supply side. For loop closure of lines with high phase angle difference, this invention uses a small-capacity series compensation circuit to achieve minimum power loop closure. When one side disconnects the loop, a fast bypass circuit is used in conjunction with a series compensation transformer with high short-time overload capacity. The three-phase inverter is switched off. In the solution of this invention, the series compensation circuit does not need to bear the entire load on the original power bus, but only needs to be designed according to the power required to generate the compensation voltage. Therefore, the solution of this invention can significantly reduce the required three-phase inverter capacity, requiring only a small amount of energy storage to support the DC bus voltage, thereby significantly reducing the cost and size of the device, making it more suitable for vehicle transportation and mobile installation scenarios.

[0032] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0033] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0034] Figure 1 This is a schematic diagram of the uninterrupted power supply loop transfer device for power distribution networks of the present invention;

[0035] Figure 2 yes Figure 1 A schematic diagram of the structure of the series compensation circuit;

[0036] Figure 3 yes Figure 2 Schematic diagram of the medium-speed bypass circuit;

[0037] Figure 4 This is a schematic diagram of the working state of the uninterrupted power supply loop transfer device for power distribution networks of the present invention;

[0038] Figure 5 This is a flowchart of the control method for the uninterrupted power supply loop transfer device in the power distribution network of the present invention;

[0039] Figure 6This is a schematic diagram of the current changes in the original supply bus, the switching supply bus, and the series compensation circuit during the loop switching of the device of the present invention.

[0040] Figure 7 This is a schematic diagram of the three-phase voltage change of the original supply bus side load when the device of the present invention is switched to a closed loop. Detailed Implementation

[0041] To facilitate understanding of the present invention, a more complete description is provided below, along with preferred embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0043] Example:

[0044] like Figures 1-4 As shown, this embodiment provides a power distribution network uninterrupted loop transfer device, which includes a loop transfer controller and a DC voltage regulator circuit, a series compensation circuit and a load switching circuit connected in sequence.

[0045] The DC voltage regulator circuit serves as the DC input of the series compensation circuit, providing voltage support.

[0046] The series compensation circuit is connected in series between the original power supply bus and the transfer power supply bus during operation to compensate for the voltage difference between the original power supply bus and the transfer power supply bus.

[0047] The load switching circuit is used to control the connection and disconnection of the series compensation circuit between the original power supply bus and the transfer power supply bus;

[0048] The loop-connection and transfer controller is used to acquire signals from the original supply bus at the loop-connection point, the transfer bus at the loop-connection point, the DC voltage regulator circuit, and the series compensation circuit, and to control the loop-connection and transfer device to complete the loop-connection and transfer between the original supply bus and the transfer bus.

[0049] like Figure 1 As shown, the DC voltage regulator circuit includes an energy storage battery. DC-DC regulated converter and DC regulated capacitor The DC-DC regulated converter The positive and negative input terminals correspond to the energy storage battery. The positive and negative terminals are connected, and the DC-DC converter is... The positive and negative output terminals are connected to the positive and negative input terminals of the series compensation circuit via a DC bus, and the DC voltage regulator capacitor... Connected in series with the DC-DC regulated converter Between the positive and negative output terminals.

[0050] Specifically, the DC voltage regulator circuit is used to provide DC bus voltage support and active power support for the closed-loop power supply device, based on the energy storage battery. Output voltage and rated DC bus voltage The relationship between the DC-DC converter A buck or boost DC voltage regulator circuit can be used. Furthermore, if the energy storage battery... The output voltage is higher than the rated voltage of the DC bus. The DC-DC regulated converter A step-down DC voltage regulator circuit is adopted; if the energy storage battery The output voltage is lower than the rated voltage of the DC bus. The DC-DC regulated converter A boost DC voltage regulator circuit is used. Both the buck DC voltage regulator circuit and the boost DC voltage regulator circuit are existing technologies and will not be described in detail in this embodiment.

[0051] More preferably, the DC-DC regulated converter The input and output ports should be connected to the energy storage battery using isolated circuits. And a series compensation circuit, thereby achieving the purpose of protecting the energy storage battery.

[0052] like Figures 1-3 As shown, the series compensation circuit includes a series compensation transformer. Three-phase inverter and fast bypass circuit The three-phase inverter The positive and negative input terminals are connected to the positive and negative output terminals of the DC voltage regulator circuit (i.e., the three-phase inverter). The positive and negative input terminals are connected to the DC-DC regulated converter. The positive and negative output terminals of the three-phase inverter are connected correspondingly via a DC bus. The output three phases and the series compensation transformer The primary winding of the series compensation transformer is connected in three phases. The three phases of the secondary winding are connected or disconnected between the original power supply bus and the transfer power supply bus via a load switching circuit; the three-phase inverter All three phases of the output terminal are equipped with fast bypass circuits. Fast bypass circuit for each phase All are connected across the series compensation transformer The corresponding primary winding of each phase is connected to the neutral point A. In this embodiment, the fast bypass circuits bridging the three-phase primary windings are respectively represented as follows: , and .

[0053] like Figure 2 As shown, the three-phase inverter It includes a three-phase full-bridge circuit and a current-limiting inductor, wherein the positive and negative input terminals of the three-phase full-bridge circuit are connected to the DC-DC regulated converter. The positive and negative output terminals are connected to each other via a DC bus. Each of the three output phases of the three-phase full-bridge circuit is connected in series with a corresponding current-limiting inductor and then to the series compensation transformer. The primary windings are connected in three phases. The current-limiting inductors connected in series on the three output phases of the three-phase full-bridge circuit in this embodiment are respectively represented as... , and Fast bypass circuit , and The input terminals are respectively connected to the current-limiting inductors of the corresponding phases. , and Output connection

[0054] The three-phase full-bridge circuit in this embodiment consists of six switching transistors and their anti-parallel diodes. Three-phase full-bridge circuits are common knowledge in the field, therefore, they will not be described in detail in this embodiment. In this embodiment, the six switching transistors and their anti-parallel diodes are respectively represented as follows: , , , , and .

[0055] like Figure 3 As shown, the fast bypass circuit Including the first anti-parallel thyristor group connected in series. and buffer reactance The first anti-parallel thyristor group The input terminal is connected to the corresponding current-limiting inductor output terminal, and the output terminal of the buffer reactor is... The first anti-parallel thyristor group is connected to the neutral point A of the three phases of the primary winding of the series compensation transformer. It includes two thyristors connected in parallel with opposite conduction directions. The fast bypass circuit... When turned on, the bypass is connected in series with the compensation transformer. The primary winding corresponding to the phase.

[0056] In this embodiment, the three output phases of the three-phase full-bridge circuit are connected in a star configuration with the series compensation transformer after being connected in series with current-limiting inductors. The primary winding is connected in three phases, and in some embodiments, a delta connection may also be used with the series compensation transformer. The primary winding of the transformer is connected in three phases; the series compensation transformer It is a three-phase transformer, the series compensation transformer It needs to have strong short-term overload capacity.

[0057] like Figure 1 and Figure 4 As shown, the load switching circuit is a three-phase circuit, and each phase circuit includes a second anti-parallel thyristor group, a first AC circuit breaker, and a second AC circuit breaker. The series compensation transformer... One end of each phase secondary winding is connected to the closing point via the corresponding phase's first AC circuit breaker and a tie switch. The original busbar on one side is connected, and the other end of each phase secondary winding is connected to the closing point via the corresponding phase's second AC circuit breaker and the tie switch. On the other side, the transfer bus is connected, and the two ends of the second anti-parallel thyristor group are respectively connected to the two ends of the secondary winding of the corresponding phase.

[0058] Furthermore, on a single-phase line, the second anti-parallel thyristor group and the series compensation transformer... The secondary winding and the connecting switch at the loop point The three are connected in parallel. Specifically, one end of the second anti-parallel thyristor group is connected to the first AC circuit breaker and the series compensation transformer. Between them, its other end is connected to the second AC circuit breaker and the series compensation transformer. between.

[0059] like Figure 1 As shown, this embodiment implements a series compensation transformer. The first AC circuit breakers connected to the original three phases of the power supply busbar are respectively denoted as: , and To realize series compensation transformer The second AC circuit breaker connected to the three phases of the transfer busbar is represented as follows: , and With series compensation transformer The three-phase second anti-parallel thyristor groups with their secondary windings connected in parallel are respectively represented as follows: , and .

[0060] Furthermore, the second anti-parallel thyristor group also includes two thyristors connected in parallel with opposite conduction directions.

[0061] Furthermore, the loop-connected power supply controller includes a sampling circuit and a microcontroller unit, wherein the sampling circuit is used to acquire the three-phase voltage of the original power supply bus. , and Three-phase voltage of the transfer bus , and Three-phase current at the loop closing point , and Three-phase inverter Output three-phase current , and Three-phase inverter Output three-phase voltage , and DC bus output voltage (i.e., DC-DC regulated converter) Output voltage and DC bus output current (i.e., DC-DC regulated converter) The microcontroller unit, based on the signal acquired by the sampling circuit, controls the DC-DC converter (output current). Three-phase inverter Fast bypass circuit The load switching circuit sends control signals to complete the closed-loop power supply.

[0062] In this embodiment, the microcontroller unit controls the loop-closing transfer device to complete the loop-closing transfer between the original supply bus and the transfer bus according to the following method:

[0063] Figure 4 middle The connecting switch at the loop closing point. This is the circuit breaker at the beginning of the original power supply bus. For the circuit breaker at the beginning of the power supply busbar, This is the transformer at the beginning of the original power supply bus. For the transformer at the beginning of the busbar side, This is the equivalent load on the original power supply bus side. This is the equivalent load on the power supply bus side. For example... Figure 5 As shown, the steps for controlling the loop-closing transfer device to complete the loop-closing transfer between the original supply bus and the transfer bus are as follows:

[0064] Connect the loop transfer device in parallel to the loop closing point via the tie switch. After connecting both ends, close the first AC circuit breaker S on the original power supply bus side of the load switching circuit. 1a S 1b S 1c ;

[0065] The sampling circuit collects the three-phase voltage of the original power supply bus, the three-phase voltage of the transfer power supply bus, the closed-loop three-phase current at the closing point, and the three-phase inverter. Output three-phase current, three-phase inverter The output three-phase voltage, DC bus output voltage, and DC bus output current;

[0066] The microcontroller unit, based on the sampled signal and the DC bus output voltage U, dc and DC bus output current I dc The DC voltage regulator circuit employs closed-loop output voltage control to adjust the DC bus voltage to its rated voltage. Voltage closed-loop control of DC voltage regulator circuits is widely known knowledge in the field of power electronics, and the specific control logic will not be described in detail in this embodiment.

[0067] The microcontroller unit acquires the voltage difference between the original power supply bus and the transfer power supply bus, as well as the series compensation transformer. The transformer ratio will change the original bus voltage. , and With the corresponding transfer bus voltage , and Difference divided by series compensation transformer The turns ratio generates voltage commands for the three-phase inverter and uses voltage-current dual closed-loop control to regulate the three-phase inverter. The output three-phase voltage is such that the three-phase voltage output by the three-phase inverter is the same as the value in the three-phase inverter voltage command; that is, the three-phase voltage output by the three-phase inverter is the voltage difference divided by the series compensation transformer. The quotient of the turns ratio makes the series compensation transformer The output voltage of the secondary winding can compensate for the voltage difference between the original power supply bus and the transfer power supply bus; voltage and current dual closed-loop control is the basic knowledge of power electronic converter control, and the specific control logic will not be described in this embodiment.

[0068] Close the second AC circuit breaker S on the side of the transfer bus in the load switching circuit. 2a S 2b S 2c Disconnect the contact switch This allows the series compensation circuit to be connected between the original power supply bus and the transfer power supply bus. In this case, the series compensation circuit only performs voltage compensation between the original power supply bus and the transfer power supply bus. If necessary, a series compensation transformer must be considered. The phase deviation caused by the series compensation transformer is compensated for by adjusting the phase deviation value in the three-phase inverter voltage command. Specifically, when the phase deviation of the series compensation transformer exceeds a threshold, the phase deviation value is used to compensate for the phase deviation value in the three-phase inverter voltage command. Then, the three-phase inverter is subjected to dual closed-loop control of voltage and current based on the compensated command. The specific compensation method is basic knowledge in this field and will not be described in detail in this embodiment.

[0069] When the three-phase inverter After the output stabilizes, the circuit breaker at the beginning of the original power supply busbar is activated. Disconnect the power supply to the original busbar side. At this time, the load on the original busbar side... The power supply is transferred to the power transfer bus via the closed-loop transfer device; three-phase inverter Output current surge;

[0070] When the three-phase inverter The output current of any one phase ( , and Exceeding the set current threshold At that time, the microcontroller unit controls the first anti-parallel thyristor group of the corresponding phase in the fast bypass circuit to conduct, while simultaneously blocking the three-phase inverter. The drive pulse causes the load current to be transferred to the fast bypass circuit; at this time, the three-phase inverter... Output current decreases, series compensation transformer The voltage at the input and output terminals begins to oscillate; since the power supply to the original bus is disconnected, the voltage of the original bus will drop slightly during the oscillation process, and no inrush current will be generated on the line.

[0071] When the voltage difference between the original supply bus and the transfer bus is less than the preset closed-loop operating voltage difference, the second anti-parallel thyristor group of the load switching circuit is turned on.

[0072] The communication switch will be closed after a delay of time T. Disconnect the first AC circuit breaker and the second AC circuit breaker, and the closed-loop power supply device is taken out of operation, completing the uninterrupted closed-loop power supply.

[0073] This embodiment simulates the loop-connection transfer process of the uninterrupted power distribution network transfer device and control method. The phase angle difference between the original supply bus and the transfer bus is 15 degrees. The active power of the load on the original supply bus side is 4 MW, the reactive power is 3 MVA, and the transformation ratio between the secondary winding and the primary winding of the series compensation transformer is 10kV / 380V.

[0074] Simulation results are as follows Figure 6 and Figure 7 As shown in the figure This refers to the phase a current in the original power supply bus. To transfer the a-phase current in the busbar, Three-phase inverter The output phase a current.

[0075] Initially, the original power supply busbar operates solely with its original load, while the transfer busbar carries a small local load. At 0.70 seconds, the loop-connecting transfer device in this embodiment has already been activated, compensating for the voltage difference between the original and transfer busbars, and an electrical connection has been established between them. At 0.70 seconds, the original power supply busbar disconnects, and the load on the original power supply busbar side is transferred to the transfer busbar side. rise, Rise. When Exceeding the threshold Subsequently, the first anti-parallel thyristor group conducts, and the three-phase inverter drive is locked; after a delay of T, the tie switch closes, and the loop transfer device is taken out of operation. Throughout the entire transfer process, there is no inrush current on either the original supply bus or the transfer bus, and the output current of the three-phase inverter is far less than the current required to transfer all the original supply side loads, proving the feasibility and advantages of the device in this embodiment.

[0076] The effect of applying the technical solution of this embodiment is:

[0077] The distribution network uninterruptible loop-connection and transfer device and control method in this embodiment, for loop-connection of lines with high phase angle difference, utilizes a small-capacity series compensation circuit to achieve minimum power loop-connection. When one side disconnects the loop, a fast bypass circuit is used in conjunction with a series compensation transformer with high short-time overload capacity. The three-phase inverter is switched off. In this embodiment, the series compensation circuit does not need to bear the entire load on the original power bus; it only needs to be designed according to the power required to generate the compensation voltage. Therefore, this embodiment can significantly reduce the required three-phase inverter capacity, requiring only a small amount of energy storage to support the DC bus voltage. This significantly reduces the cost and size of the device, making it more suitable for vehicle transportation and mobile installation scenarios.

[0078] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A power distribution network uninterrupted loop transfer device, characterized in that, It includes a loop-connected power supply controller and a DC voltage regulator circuit, a series compensation circuit, and a load switching circuit connected in sequence; the loop-connected power supply controller is used to acquire signals from the original power supply bus and the transfer power supply bus, the DC voltage regulator circuit, and the series compensation circuit at the loop-connection point, and control the loop-connected power supply device to complete the loop-connected power supply between the original power supply bus and the transfer power supply bus. The series compensation circuit includes a series compensation transformer, a three-phase inverter, and a fast bypass circuit. The input terminal of the three-phase inverter is connected to the output terminal of the DC voltage regulator circuit via a DC bus. The three phases of the output terminal of the three-phase inverter are connected to the three phases of the primary winding of the series compensation transformer. The three phases of the secondary winding of the series compensation transformer are connected to the primary power supply bus and the secondary power supply bus via a load switching circuit, so that the series compensation circuit can be connected or disconnected between the primary power supply bus and the secondary power supply bus through the load switching circuit. Each of the three phases of the output terminal of the three-phase inverter is equipped with a fast bypass circuit. When the fast bypass circuit is turned on, it bypasses the corresponding phase of the primary winding of the series compensation transformer. The DC voltage regulator circuit includes an energy storage battery, a DC voltage regulator converter, and a DC voltage regulator capacitor. The positive and negative input terminals of the DC voltage regulator converter are connected to the positive and negative terminals of the energy storage battery, respectively. The positive and negative output terminals of the DC voltage regulator converter are connected to the positive and negative input terminals of the three-phase inverter via a DC bus. The DC voltage regulator capacitor is connected in series between the positive and negative output terminals of the DC voltage regulator converter. Each phase of the load switching circuit includes a second anti-parallel thyristor group, a first AC circuit breaker, and a second AC circuit breaker. One end of the secondary winding of each phase of the series compensation transformer is connected to the original power supply bus on one side of the tie switch at the closing point through the first AC circuit breaker of the corresponding phase. The other end of the secondary winding of each phase is connected to the transfer power supply bus on the other side of the tie switch at the closing point through the second AC circuit breaker of the corresponding phase. The two ends of the second anti-parallel thyristor group are respectively connected to the two ends of the secondary winding of the corresponding phase.

2. The uninterrupted power supply loop transfer device for power distribution networks according to claim 1, characterized in that, The three-phase inverter includes a three-phase full-bridge circuit and a current-limiting inductor. The positive and negative input terminals of the three-phase full-bridge circuit are connected to the positive and negative output terminals of the DC voltage regulator circuit through a DC bus. The three output phases of the three-phase full-bridge circuit are connected in series with the corresponding current-limiting inductors and then connected to the three phases of the primary winding of the series compensation transformer. The fast bypass circuit is connected to the output terminal of the current-limiting inductor of the corresponding phase.

3. The uninterrupted power supply loop transfer device for power distribution networks according to claim 1, characterized in that, If the output voltage of the energy storage battery is higher than the rated voltage of the DC bus, the DC-DC converter adopts a buck DC-DC regulator circuit; if the output voltage of the energy storage battery is lower than the rated voltage of the DC bus, the DC-DC converter adopts a boost DC-DC regulator circuit.

4. The uninterrupted power supply loop transfer device for power distribution networks according to claim 2, characterized in that, The fast bypass circuit includes a first anti-parallel thyristor group and a buffer reactor connected in series. The input terminal of the first anti-parallel thyristor group is connected to the output terminal of the corresponding current-limiting inductor, and the output terminal of the buffer reactor is connected to the neutral point of the three phases of the primary winding of the series compensation transformer.

5. The uninterrupted power supply loop transfer device for power distribution networks according to claim 4, characterized in that, The first anti-parallel thyristor group and the second anti-parallel thyristor group each include two thyristors connected in parallel and the conduction directions of the two thyristors are opposite.

6. The uninterrupted power supply loop transfer device for power distribution networks according to claim 1, characterized in that, The loop-connection power transfer controller includes a sampling circuit and a microcontroller unit. The sampling circuit is used to collect the three-phase voltage of the original power supply bus, the three-phase voltage of the transfer power supply bus, the loop-connection three-phase current at the loop-connection point, the three-phase current output by the three-phase inverter, the three-phase voltage output by the three-phase inverter, the DC bus output voltage, and the DC bus output current. The microcontroller unit sends control signals to the DC-DC converter, the three-phase inverter, the fast bypass circuit, and the load switching circuit based on the signals collected by the sampling circuit to complete the loop-connection power transfer.

7. A control method for a power distribution network uninterruptible loop transfer device as described in any one of claims 1-6, characterized in that, include: After connecting the loop transfer device in parallel to both ends of the tie switch at the loop point, close the first AC circuit breaker in the load switching circuit. Collect the three-phase voltage of the original power supply bus, the three-phase voltage of the transfer power supply bus, the three-phase current of the loop connection point, the three-phase current output by the three-phase inverter, the three-phase voltage output by the three-phase inverter, the DC bus output voltage, and the DC bus output current. Based on the DC output voltage and the DC bus output current, the DC voltage regulator circuit performs closed-loop control of the output voltage to adjust the DC bus voltage to the rated voltage. Divide the three-phase voltage difference between the original supply bus and the transfer supply bus by the turns ratio of the series compensation transformer, and adjust the three-phase voltage output of the three-phase inverter according to the calculation results so that the output voltage of the secondary winding of the series compensation transformer can compensate for the voltage difference between the original supply bus and the transfer supply bus. Close the second AC circuit breaker in the load switching circuit so that the series compensation circuit can be connected between the original power supply bus and the transfer power supply bus to compensate for the voltage difference. Once the three-phase inverter output stabilizes, the power supply to the original supply bus is disconnected, and the load on the original supply bus is transferred to the transfer bus via the loop transfer device, causing a surge in the output current of the three-phase inverter. When the current of any one phase of the three-phase inverter output exceeds the set current threshold At this time, the first anti-parallel thyristor group in the control fast bypass circuit is turned on, and the drive pulse of the three-phase inverter is blocked, so that the load current is transferred to the fast bypass circuit; at this time, the output current of the three-phase inverter decreases, and the voltage at the input and output terminals of the series compensation transformer begins to oscillate. During the oscillation, the voltage of the original power supply bus decreases. When the voltage difference between the original supply bus and the transfer bus is less than the preset closed-loop operating voltage difference, the second anti-parallel thyristor group of the load switching circuit is turned on. After a delay of time T, the connecting switch at the loop connection point is closed, the first AC circuit breaker and the second AC circuit breaker are disconnected, the loop transfer device is taken out of operation, and the uninterrupted loop transfer is completed.

8. The control method for the uninterrupted power supply loop transfer device in the distribution network according to claim 7, characterized in that, When adjusting the three-phase voltage output of the three-phase inverter based on the calculation results, a three-phase inverter voltage command is generated based on the calculation results. When the phase deviation of the series compensation transformer exceeds the threshold, phase compensation is performed on the value in the three-phase inverter voltage command based on the value of the phase deviation. Then, the three-phase inverter is subjected to voltage and current dual closed-loop control so that the three-phase voltage output of the three-phase inverter is the same as the value in the three-phase inverter voltage command.

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