Power distribution network non-power-outage loop closing transfer device and control method

Abstract

The invention provides a power distribution network non-power-outage loop-closing power transfer device and a control method. The device comprises a loop-closing power transfer controller, and a direct-current voltage stabilizing circuit, a series compensation circuit and a load switching circuit which are connected in sequence, the direct-current voltage stabilizing circuit serves as direct-current input of the series compensation circuit and is used for providing voltage support; the series compensation circuit is connected in series between the original supply bus and the transfer supply bus during working and is used for compensating the voltage difference between the original supply bus and the transfer supply bus; the load switching circuit is used for controlling the connection and disconnection of the series compensation circuit between the original supply bus and the transfer supply bus; and the closed-loop transfer controller is used for performing signal acquisition on the original supply bus, the transfer bus, the direct-current voltage stabilizing circuit and the series compensation circuit, and controlling the closed-loop transfer device to complete closed-loop transfer between the original supply bus and the transfer bus. The series compensation circuit does not need to bear all loads on an original supply bus, and only needs to be designed according to the power required for generating the compensation voltage, so that the capacity of the required power electronic converter is reduced.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of power distribution network operation, and particularly relates to a power distribution network non-power-off loop closing and power supply device and a control method. BACKGROUND

[0002] The 110kV and below power grid in China is usually in an open loop radial power supply mode. When the power supply of the power grid needs to be adjusted due to reasons such as fault elimination and planned maintenance of the power grid line, in order to avoid the influence on the power supply of users, a short-time loop closing and power supply is usually adopted. However, due to the unbalanced load current between different power supply areas (different equivalent impedance), different main transformer winding connection modes (‘△' connection and ‘Y' connection), and different power supply from different 220kV lines, there may be a high phase angle difference between the voltage phase quantities on both sides of the loop closing point. Direct loop closing under high phase angle difference may generate a large loop closing impact current, which may cause serious consequences such as protection tripping, power grid line disconnection and equipment burning, and must be limited.

[0003] A Chinese patent with the publication number CN112803407B discloses a low-voltage power distribution network seamless loop closing and power supply method and system based on a parallel converter. The principle is to first realize flexible interconnection between the original supply bus and the transferred supply bus by using a parallel converter; then adjust the output power of the parallel converter so that the output power of the original supply bus is zero; then cut off the power supply of the original supply bus, at this time the load on the original supply bus is supplied by the transferred supply bus through the parallel converter; next, adjust the voltage of the parallel converter so that the voltage vector difference between the transferred supply bus and the original supply bus is within the loop closing range; then close the switch between the transferred supply bus and the original supply bus, since the voltage difference on both sides has been controlled within the loop closing range, the impact current is very low; finally, the parallel converter is exited to realize non-power-off loop closing and power supply. In this scheme, the parallel converter needs to bear all the loads on the original supply bus for a long time, and a large-capacity power electronic converter is needed, which has problems such as large size, high cost and complex control.

[0004] A Chinese patent application with the publication number CN119695866A discloses a power distribution network non-power-off load transfer control method, system, device and storage medium based on series compensation. The difference between this scheme and the Chinese patent with the publication number CN112803407B is that this scheme realizes flexible interconnection between the original power supply bus and the transferred power supply bus by using a series compensation voltage source. After realizing full load transfer through the series compensation voltage source, the series compensation voltage is adjusted to be within the loop closing allowable range, the switch between the transferred supply bus and the original supply bus is closed, and the series compensation voltage source is exited. Although the series compensation voltage source in this scheme requires smaller device capacity than the parallel converter, the device capacity required by the series compensation voltage source is still large because the full load on the original supply bus flows through the branch where the series compensation voltage source is located for a long time, and the cost and size are still high.

[0005] Therefore, there is an urgent need for a power distribution network non-power-off loop transfer device and control method to solve the problems in the prior art. SUMMARY

[0006] The application aims to provide a power distribution network non-power-off loop transfer device, and aims to solve the problems in the prior art that power electronic devices need to bear the entire load on the original supply bus for a long time, need large-capacity power electronic devices, and have problems such as large size, high cost, and complex control. The application aims to provide a power distribution network non-power-off loop transfer device, and aims to solve the problems in the prior art that power electronic devices need to bear the entire load on the original supply bus for a long time, need large-capacity power electronic devices, and have problems such as large size, high cost, and complex control. The DC voltage stabilizing circuit is used as a DC input of the series compensation circuit and is used to provide voltage support. The series compensation circuit is connected in series between the original supply bus and the transfer bus when working, and is used to compensate for 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 from the original supply bus at the loop point, the transfer bus at the loop point, 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.

[0007] Preferably, the series compensation circuit comprises 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 stabilizing circuit through a DC bus, the output three-phase of the three-phase inverter is connected to the primary winding three-phase of the series compensation transformer, the secondary winding three-phase of the series compensation transformer is connected to the original supply bus and the transfer bus through the load switching circuit, and the output three-phase of the three-phase inverter is provided with the fast bypass circuit, which bypasses the corresponding phase of the primary winding of the series compensation transformer when conducting.

[0008] Preferably, the three-phase inverter comprises 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 stabilizing circuit through a DC bus, the output three-phase of the three-phase full-bridge circuit is connected to the primary winding three-phase of the series compensation transformer after being connected to the corresponding current-limiting inductor in series, and the fast bypass circuit is connected to the output terminal of the corresponding current-limiting inductor.

[0009] Preferably, the direct current stabilizing circuit comprises an energy storage battery, a direct current stabilizing converter and a direct current stabilizing capacitor, the positive and negative input terminals of the direct current stabilizing converter are connected to the positive and negative terminals of the energy storage battery, the positive and negative output terminals of the direct current stabilizing converter are connected to the positive and negative input terminals of the three-phase inverter through a direct current bus, and the direct current stabilizing capacitor is connected in series between the positive and negative output terminals of the direct current stabilizing converter.

[0010] Preferably, if the output voltage of the energy storage battery is higher than the rated voltage of the direct current bus, the direct current stabilizing converter adopts a step-down direct current stabilizing circuit; if the output voltage of the energy storage battery is lower than the rated voltage of the direct current bus, the direct current stabilizing converter adopts a step-up direct current stabilizing circuit.

[0011] Preferably, the fast bypass circuit comprises a first anti-parallel thyristor group and a buffer reactance connected in series, the input terminal of the first anti-parallel thyristor group is connected to the output terminal of a corresponding current-limiting inductor, and the output terminal of the buffer reactance is connected to the neutral point of the three-phase primary winding of the series compensation transformer.

[0012] Preferably, each phase of the load switching circuit comprises a second anti-parallel thyristor group, a first AC circuit breaker and a second AC circuit breaker, one end of each phase of the secondary winding of the series compensation transformer is connected to the original supply bus through the first AC circuit breaker of the corresponding phase and the contact switch of the loop-through point on one side, the other end of each phase of the secondary winding is connected to the transfer supply bus through the second AC circuit breaker of the corresponding phase and the contact switch of the loop-through point on the other side, and the two ends of the second anti-parallel thyristor group are connected to the two ends of the corresponding phase of the secondary winding.

[0013] Preferably, the first anti-parallel thyristor group and the second anti-parallel thyristor group each comprise two thyristors connected in parallel, and the conduction directions of the two thyristors are opposite.

[0014] Preferably, the loop-through transfer control device comprises a sampling circuit and a micro control unit, the sampling circuit is used to collect the three-phase voltage of the original supply bus, the three-phase voltage of the transfer supply bus, the loop-through three-phase current of the loop-through point, the three-phase current output by the three-phase inverter, the three-phase voltage output by the three-phase inverter, the output voltage of the direct current bus and the output current of the direct current bus, and the micro control unit sends control signals to the direct current stabilizing converter, the three-phase inverter, the fast bypass circuit and the load switching circuit according to the signals collected by the sampling circuit to complete the loop-through transfer.

[0015] The application also provides a control method of the power distribution network loop-through transfer device without power interruption, which comprises the following steps: After connecting the loop transfer device in parallel with the two ends of the tie switch at the loop point, closing the first AC circuit breaker on the side of the original supply bus in the load switching circuit, collecting 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; According to the DC output voltage and the DC bus output current, the output voltage of the DC voltage stabilizing circuit is controlled in a closed loop, and the voltage of the DC bus is adjusted to the rated voltage. The three-phase voltage difference between the original supply bus and the transfer bus is divided by the transformation ratio of the series compensation transformer, and the three-phase voltage output by the three-phase inverter is adjusted according to the calculation result, 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 bus. The second AC circuit breaker on the side of the transfer bus in the load switching circuit is closed, so that the series compensation circuit is connected between the original supply bus and the transfer bus to compensate for the voltage difference. When the three-phase inverter output is stable, the power supply on the side of the original supply bus is disconnected, the load on the side of the original supply bus is transferred to the transfer bus through the loop transfer device, and the output current of the three-phase inverter increases sharply. When any one of the three-phase inverter output currents exceeds the set current threshold , the first anti-parallel thyristor group in the fast bypass circuit is turned on, and the driving pulse of the three-phase inverter is blocked at the same time, 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 ends of the series compensation transformer begins to oscillate, and the voltage of the original supply bus decreases during the oscillation process. When the voltage difference between the original supply bus and the transfer bus is less than the preset loop operation voltage difference, the second anti-parallel thyristor group of the load switching circuit is turned on. After a delay of T time, the tie switch is closed, the first AC circuit breaker and the second AC circuit breaker are disconnected, the loop transfer device exits the operation, and the loop transfer without power interruption is completed.

[0016] Further, when adjusting the three-phase voltage output by the three-phase inverter according to the calculation result, the three-phase inverter voltage instruction is generated according to the calculation result, and when the phase deviation of the series compensation transformer exceeds the threshold, the value in the three-phase inverter voltage instruction is phase compensated according to the value of the phase deviation, and then the voltage and current of the three-phase inverter are controlled in a double closed loop, so that the three-phase voltage output by the three-phase inverter is the same as the value in the three-phase inverter voltage instruction.

[0017] The technical scheme of the application has the following beneficial effects: The application utilizes the fast bypass circuit in the series compensation circuit, and the working principle is that: at the beginning, the closing device is closed, the series compensation device only compensates the phase difference of the two sides, and the current is very small; then the switch on one side is pulled open, the load current is transferred from the original power supply side to the transfer power supply side, the current of the series compensation device increases, and after reaching a certain threshold, the fast bypass circuit acts, bypassing the series compensation circuit, so that it will not bear the entire load current of the original power supply side. The three-phase inverter is cut out. In the scheme of 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 a compensation voltage. Therefore, the scheme of the application can greatly reduce the required capacity of the three-phase inverter, only needs a small energy storage to support the DC bus voltage, and thus can significantly reduce the device cost and volume, and is more suitable for vehicle transportation and mobile installation scenes.

[0018] In addition to the purposes, features and advantages described above, the application has other purposes, features and advantages. The application will be further described below with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0019] The drawings that form a part of this application are used to provide a further understanding of the application, and the illustrative embodiments of the application and their description serve to explain the application, and do not constitute an improper limitation on the application. In the drawings: Figure 1 is a structural schematic diagram of the power distribution network non-stop closing and transfer supply device of the application; Figure 2 is Figure 1 a structural schematic diagram of the series compensation circuit in the application; Figure 3 is Figure 2 a structural schematic diagram of the fast bypass circuit in the application; Figure 4 is a working state schematic diagram of the power distribution network non-stop closing and transfer supply device of the application; Figure 5 is a control method flow chart of the power distribution network non-stop closing and transfer supply device of the application; Figure 6 is a schematic diagram of current changes in the original supply bus, the transfer supply bus and the series compensation circuit when the device of the application is in closing and transfer supply; Figure 7 is a schematic diagram of three-phase voltage changes of the load on the original supply bus when the device of the application is in closing and transfer supply. DETAILED DESCRIPTION

[0020] 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.

[0021] 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.

[0022] Example: 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. The DC voltage regulator circuit serves as the DC input of the series compensation circuit, providing voltage support. 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. 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; 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.

[0023] like Figure 1 As shown, the DC voltage regulator circuit includes an energy storage battery. DC-DC regulated converter and DC voltage regulator 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.

[0024] 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 voltage stabilizing converter A buck or a boost type DC voltage stabilizing circuit can be adopted. Further, if the energy storage battery outputs a voltage higher than the rated voltage of the DC bus , the DC voltage stabilizing converter adopts a buck type DC voltage stabilizing circuit; if the energy storage battery outputs a voltage lower than the rated voltage of the DC bus , the DC voltage stabilizing converter adopts a boost type DC voltage stabilizing circuit. The buck type DC voltage stabilizing circuit and the boost type DC voltage stabilizing circuit are both prior arts, which will not be described in detail in the present embodiment.

[0025] Further preferably, the input port and the output port of the DC voltage stabilizing converter are connected to the energy storage battery and the series compensation circuit respectively by using a circuit with isolation capability, so as to protect the energy storage battery.

[0026] As shown in Figures 1-3 , the series compensation circuit comprises 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 stabilizing circuit (i.e. the positive and negative input terminals of the three-phase inverter are connected to the positive and negative output terminals of the DC voltage stabilizing converter through the DC bus), the output three-phase of the three-phase inverter is connected to the primary winding three-phase of the series compensation transformer , the secondary winding three-phase of the series compensation transformer is connected to or cut off from the original DC bus and the transferred DC bus through a load switching circuit; the output three-phase of the three-phase inverter is provided with a fast bypass circuit , and the fast bypass circuit of each phase is connected across the corresponding primary winding of the series compensation transformer and the neutral point A. The fast bypass circuits of the three-phase primary windings in the present embodiment are respectively represented as , and .

[0027] As shown in Figure 2 , 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 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 .

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] like Figure 1 As shown, this embodiment implements a series compensation transformer. The first AC circuit breakers connected to the original three-phase 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 bus 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 .

[0033] Furthermore, the second anti-parallel thyristor group also includes two thyristors connected in parallel with opposite conduction directions.

[0034] 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.

[0035] 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: 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: 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 ; 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; 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. 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. 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. 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; 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. 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. 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] The effect of applying the technical solution of this embodiment is: 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.

[0040] 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 transfer 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 transfer 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.

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, 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.

4. The uninterrupted power supply loop transfer device for power distribution networks according to claim 3, 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.

5. 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.

6. The uninterrupted power supply loop transfer device for power distribution networks according to claim 5, characterized in that, 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.

7. The uninterrupted power supply loop transfer device for power distribution networks according to claim 6, 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.

8. 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.

9. A control method for a power distribution network uninterruptible loop transfer device as described in any one of claims 1-8, 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.

10. The control method for the uninterrupted power supply loop transfer device in the distribution network according to claim 9, 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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