A low-voltage distribution area interconnection loop device

Abstract

The application discloses a kind of low-voltage distribution area's contact ring device. Wherein the device includes switch unit, contact ring controller and series voltage compensation unit;First transformer and second transformer respectively to first low-voltage bus and second low-voltage bus output first and second power supply voltage through series voltage compensation unit;Contact ring controller determines the voltage parameter at first low-voltage bus and second low-voltage bus;Based on the parameter deviation between the voltage parameter of first bus voltage and the voltage parameter of second bus voltage, determine the voltage to be compensated in first power supply voltage and second power supply voltage, and determine the target voltage parameter of compensation voltage;Control series voltage compensation unit generates the above-mentioned compensation voltage, and based on compensation voltage to voltage compensation to be compensated voltage;Control switch unit to turn on, to carry out contact ring operation to first low-voltage bus and second low-voltage bus. The above-mentioned scheme can improve the safety of area contact ring.

Description

Technical Field

[0001] This invention relates to the field of power supply control technology, and in particular to a connection and loop closing device for a low-voltage distribution substation. Background Technology

[0002] In power distribution network maintenance scenarios, connecting the low-voltage busbars of two low-voltage distribution substations via a loop enables uninterrupted load transfer between the two substations, ensuring continuous power supply to the equipment in each substation. However, if a voltage difference exists between the two low-voltage busbars at the moment of loop connection, a significant inrush current can be generated, potentially damaging the equipment. Therefore, strictly ensuring the safety of the loop connection operation is a prerequisite for uninterrupted power transfer operations in low-voltage power distribution networks.

[0003] However, most existing transformer substation interconnection loop control schemes only monitor the output voltage of the transformer supplying power to the low-voltage busbar, without synchronously detecting and comparing the actual operating voltages of the two low-voltage busbar sections. Since the voltage status of the two low-voltage busbar sections deviates from the transformer output voltage due to line voltage drop and real-time load, determining whether loop closing operation can be performed based solely on the transformer output voltage can easily lead to misjudgments of the voltage matching status of each low-voltage busbar, significantly increasing the safety risks of loop closing operation. Summary of the Invention

[0004] In view of this, this application provides a communication loop-closing device for a low-voltage distribution radio area, the main purpose of which is to solve the technical problem of high safety risks in loop-closing operation.

[0005] According to a first aspect of the present invention, a connection loop closing device for a low-voltage distribution substation is provided, the device comprising a series voltage compensation unit, a switching unit, and a loop closing controller; The first input terminal of the series voltage compensation unit is connected to an external first transformer, and the first output terminal of the series voltage compensation unit is connected to a first low-voltage bus to receive a first power supply voltage from the first transformer and supply power to the first low-voltage bus. The second input terminal of the series voltage compensation unit is connected to the external second transformer, and the second output terminal of the series voltage compensation unit is connected to the second low-voltage bus to receive the second power supply voltage from the second transformer and supply power to the second low-voltage bus. The switching unit is connected in series between the first low-voltage bus and the second low-voltage bus, and the loop controller is connected to the series voltage compensation unit and the switching unit respectively. The loop closing controller is configured to perform the following processes: The loop controller determines the voltage parameters of the first bus voltage at the first low-voltage bus and the voltage parameters of the second bus voltage at the second low-voltage bus. Based on the parameter deviation between the voltage parameters of the first bus voltage and the voltage parameters of the second bus voltage, the voltage to be compensated is determined between the first supply voltage and the second supply voltage, and the target voltage parameter of the compensation voltage is determined. The series voltage compensation unit is controlled to generate the compensation voltage having the target voltage parameters, and voltage compensation is performed on the voltage to be compensated based on the compensation voltage; The switching unit is controlled to turn on in order to perform a loop-closing operation on the first low-voltage bus and the second low-voltage bus.

[0006] In an optional embodiment, the high-voltage side of the first transformer is connected to an external first high-voltage bus, and the low-voltage side of the first transformer is connected to a first access terminal of the series voltage compensation unit; the high-voltage side of the second transformer is connected to an external second high-voltage bus, and the low-voltage side of the second transformer is connected to a second access terminal of the series voltage compensation unit.

[0007] In an optional embodiment, the voltage parameters include voltage amplitude and voltage phase; the loop controller, based on the parameter deviation between the voltage parameters of the first bus voltage and the second bus voltage, determines the voltage to be compensated from the first supply voltage and the second supply voltage, and determines the target voltage parameters of the compensation voltage, including: the loop controller, in the first bus voltage and the second bus voltage, determines the bus voltage with the lower voltage amplitude as the bus voltage to be adjusted, and determines the bus voltage with the higher voltage amplitude as the reference bus voltage; determines the first supply voltage or the second supply voltage corresponding to the bus voltage to be adjusted as the voltage to be compensated; and compares the voltage amplitude of the reference bus voltage with the voltage parameters of the second bus voltage. The difference in voltage amplitude between the bus voltages to be adjusted is determined as the target voltage amplitude in the target voltage parameters; the phase difference between the voltage phase of the bus voltage to be adjusted and the voltage phase of the reference bus voltage is determined, and twice the value of the phase difference is determined as the phase adjustment amount; when the voltage phase of the bus voltage to be adjusted leads the voltage phase of the reference bus voltage, the phase adjustment amount is subtracted from the voltage phase of the bus voltage to be adjusted to obtain the target voltage phase in the target voltage parameters; when the voltage phase of the bus voltage to be adjusted lags behind the voltage phase of the reference bus voltage, the voltage phase of the bus voltage to be adjusted is added to the phase adjustment amount to obtain the target voltage phase in the target voltage parameters.

[0008] In an optional embodiment, the loop controller controls the series voltage compensation unit to generate the compensation voltage having the target voltage parameters, and performs voltage compensation on the voltage to be compensated based on the compensation voltage, including: the loop controller controls the series voltage compensation unit to generate the compensation voltage, wherein the voltage amplitude of the compensation voltage is the target voltage amplitude, and the voltage phase of the compensation voltage is the target voltage phase; and the compensation voltage is superimposed on the voltage to be compensated to perform voltage compensation on the voltage to be compensated.

[0009] In an optional embodiment, the series voltage compensation unit includes a first series voltage compensation unit and a second series voltage compensation unit; the input terminal of the first series voltage compensation unit is connected to the first transformer, and the output terminal of the first series voltage compensation unit is connected to the first low-voltage bus; the input terminal of the second series voltage compensation unit is connected to the second transformer, and the output terminal of the second series voltage compensation unit is connected to the second low-voltage bus; the output terminal of the loop controller is connected to the control terminal of the first series voltage compensation unit and the control terminal of the second series voltage compensation unit respectively; when the first supply voltage is the voltage to be compensated, the loop controller is used to control the first series voltage compensation unit to generate the compensation voltage and to compensate the first supply voltage; when the second supply voltage is the voltage to be compensated, the loop controller is used to control the second series voltage compensation unit to generate the compensation voltage and to compensate the second supply voltage.

[0010] In an optional embodiment, the first series voltage compensation unit includes a first inverter and a first series-coupled transformer; the DC input terminal of the first inverter is connected to an external DC power supply, the control terminal of the first inverter is connected to the output terminal of the loop controller, the AC output terminal of the first inverter is connected to the first primary winding of the first series-coupled transformer, and the first secondary winding of the first series-coupled transformer is connected in series between the first transformer and the first low-voltage bus; the loop controller is used to control the first inverter to generate the compensation voltage when the first supply voltage is the voltage to be compensated, and to apply the compensation voltage to the first primary winding, so that the compensation voltage is superimposed on the voltage to be compensated on the branch where the first secondary winding is located, so as to perform voltage compensation on the voltage to be compensated.

[0011] In an optional embodiment, the second series voltage compensation unit includes a second inverter and a second series-coupled transformer; the DC input terminal of the second inverter is connected to an external DC power supply, the control terminal of the second inverter is connected to the output terminal of the loop controller, the AC output terminal of the second inverter is connected to the second primary winding of the second series-coupled transformer, and the second secondary winding of the second series-coupled transformer is connected in series between the second transformer and the second low-voltage bus; the loop controller is used to control the second inverter to generate the compensation voltage when the second supply voltage is the voltage to be compensated, and to apply the compensation voltage to the second primary winding, so that the compensation voltage is superimposed on the voltage to be compensated on the branch where the second secondary winding is located, so as to perform voltage compensation on the voltage to be compensated.

[0012] In an optional embodiment, the switching unit includes a first switch and a second switch; a first terminal of the first switch is connected to the first low-voltage bus, a second terminal of the first switch is connected to the first terminal of the second switch, and a second terminal of the second switch is connected to the second low-voltage bus; the control terminal of the loop controller is connected to the control terminal of the first switch and the control terminal of the second switch respectively to control the on / off state of the first switch and the second switch.

[0013] In an optional embodiment, the interconnection and loop-closing device of the low-voltage distribution substation further includes a rectifier unit; the AC side of the rectifier unit is connected between the first switch and the second switch, and the rectifier unit is used to obtain electrical energy from the first low-voltage bus or the second low-voltage bus and to supply power to the first series voltage compensation unit and the second series voltage compensation unit.

[0014] In an optional embodiment, the rectifier unit includes a transformer unit and a rectifier; the low-voltage side of the transformer unit is connected between the first switch and the second switch, and the high-voltage side of the transformer unit is connected to the AC input terminal of the rectifier; the transformer unit is used to obtain AC power supply voltage from the first low-voltage bus or the second low-voltage bus, and to step up the AC power supply voltage, sending the stepped-up AC power supply voltage to the rectifier; the DC terminal of the rectifier is connected to the power supply terminal of the first series voltage compensation unit and the power supply terminal of the second series voltage compensation unit, and is used to convert the AC power supply voltage into a DC power supply voltage to power the first series voltage compensation unit and the second series voltage compensation unit based on the DC power supply voltage.

[0015] This invention provides a low-voltage distribution substation interconnection loop closing device. By real-time acquisition of the actual voltage parameters of two low-voltage busbars, and by selecting the voltage to be compensated based on the actual voltage difference between the low-voltage busbars and performing voltage compensation, the device can eliminate the voltage deviation between the two busbars. It avoids misjudgments of the loop closing conditions caused by relying solely on the transformer outlet voltage, suppresses the inrush circulating current generated during closing, effectively reduces the probability of equipment damage, and significantly improves the reliability and safety of the distribution substation interconnection loop closing operation.

[0016] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0017] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings: Figure 1 This illustration shows one of the structural schematic diagrams of a communication loop-closing device for a low-voltage distribution radio area provided in an embodiment of the present invention; Figure 2 This is a second schematic diagram of the structure of a communication loop-closing device for a low-voltage distribution radio area provided in an embodiment of the present invention; Figure 3 This is shown as a third schematic diagram of the structure of a communication loop-closing device for a low-voltage distribution radio area provided in an embodiment of the present invention; Figure 4 The fourth schematic diagram shows the structure of a communication loop-closing device for a low-voltage distribution radio area provided in an embodiment of the present invention. Detailed Implementation

[0018] The present invention will be described in detail below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the present application can be combined with each other.

[0019] Currently, in power distribution network maintenance scenarios, connecting and looping the low-voltage busbars of two low-voltage distribution substations enables uninterrupted load transfer between the two substations, ensuring uninterrupted power supply to the equipment in each substation. However, if a voltage difference exists between the two low-voltage busbars at the moment of loop connection, a significant inrush current will be generated, potentially damaging the equipment. Therefore, strictly ensuring the safety of loop connection operations is a prerequisite for uninterrupted power transfer operations in low-voltage distribution networks. However, most existing substation interconnection loop connection control schemes only monitor the output voltage of the transformer supplying power to the low-voltage busbars, without synchronously detecting and comparing the actual operating voltages of the two low-voltage busbars. Furthermore, the voltage status of the two low-voltage busbars deviates significantly from the transformer output voltage due to line voltage drop and real-time load. If the loop connection operation is determined based solely on the transformer output voltage, it is easy to misjudge the busbar voltage matching status, significantly increasing the safety risks of the loop connection operation.

[0020] To address the above problems, in one embodiment, such as Figure 1 As shown, a connection loop closing device for a low-voltage distribution transformer area is provided. Taking the use of this device to perform loop closing operation on two low-voltage distribution transformer areas as an example, the connection loop closing device for the low-voltage distribution transformer area consists of a voltage compensation unit 100, a switching unit 200, and a loop closing controller 300 connected in series. Here, the loop closing controller 300 can be a computer device such as a microcontroller or a digital signal processor.

[0021] Specifically, the first input terminal of the series voltage compensation unit 100 is connected to the external first transformer T1, and the first output terminal of the series voltage compensation unit 100 is connected to the first low-voltage bus L1 to receive the first power supply voltage from the first transformer T1 and supply power to the first low-voltage bus L1.

[0022] Here, the high-voltage side winding coil of the first transformer T1 is connected to the external first high-voltage bus H1 that transmits 10kV high-voltage electricity to obtain high-voltage electricity. The low-voltage side winding coil of the first transformer T1 is connected to the first access terminal of the series voltage compensation unit 100. The first transformer T1 can convert 10kV high-voltage electricity into 0.4kV low-voltage electricity, and transmit the low-voltage electricity to the first low-voltage bus L1 of the first low-voltage distribution substation through the series voltage compensation unit 100, so that the electrical equipment in the first low-voltage distribution substation can obtain power from the first low-voltage bus L1.

[0023] Furthermore, the second input terminal of the series voltage compensation unit 100 is connected to the external second transformer T2, and the second output terminal of the series voltage compensation unit 100 is connected to the second low-voltage bus L2 to receive the second supply voltage from the second transformer T2 and supply power to the second low-voltage bus L2. Here, the high-voltage side winding of the second transformer T2 is connected to the external second high-voltage bus H2 to obtain high-voltage electricity, and the low-voltage side winding of the second transformer T2 is connected to the second input terminal of the series voltage compensation unit 100. The second transformer T2 can convert 10kV high-voltage electricity into 0.4kV low-voltage electricity, and transmit the low-voltage electricity to the second low-voltage bus L2 of the second low-voltage distribution substation via the second series voltage compensation unit 200, so that the electrical equipment in the second low-voltage distribution substation can obtain power from the second low-voltage bus L2.

[0024] Furthermore, the switching unit 200 is connected in series between the first low-voltage bus L1 and the second low-voltage bus L2, and the output terminal of the loop controller 300 is connected to the control terminal of the series voltage compensation unit 100 and the control terminal of the switching unit 200 respectively, so as to control the series voltage compensation unit and the switching unit 300. Furthermore, the loop-closing controller 300 is configured to perform the following processes: First, the loop controller 300 determines the voltage parameters of the first bus voltage at the first low-voltage bus L1 and the voltage parameters of the second bus voltage at the second low-voltage bus L2. Here, the series voltage compensation unit 100 generates the first bus voltage at the first low-voltage bus L1 by outputting a first supply voltage to the first low-voltage bus L1, and generates the second bus voltage at the second low-voltage bus L2 by outputting a second supply voltage to the second low-voltage bus L1.

[0025] Specifically, the loop controller 300 can acquire voltage parameters of the first bus voltage at the first low-voltage bus L1 based on a first voltage sensor (not shown in the figure) installed at the first low-voltage bus L1. These voltage parameters include voltage amplitude and voltage phase. Furthermore, the loop controller 300 can acquire voltage parameters of the second bus voltage at the second low-voltage bus L2 based on a second voltage sensor (not shown in the figure) installed at the second low-voltage bus L2. These voltage parameters include voltage amplitude and voltage phase.

[0026] Then, based on the parameter deviation between the voltage parameters of the first bus voltage and the voltage parameters of the second bus voltage, the voltage to be compensated is determined between the first supply voltage and the second supply voltage, and the target voltage parameter of the compensation voltage is determined. Specifically, the loop controller can determine the bus voltage with the lower voltage amplitude between the first bus voltage and the second bus voltage as the bus voltage to be adjusted, and the bus voltage with the higher voltage amplitude as the reference bus voltage. For example, the controller compares the first voltage amplitude of the first bus voltage with the second voltage amplitude of the second bus voltage. If the first voltage amplitude is higher than the second voltage amplitude, the second bus voltage is determined as the bus voltage to be adjusted, and the first bus voltage is determined as the reference bus voltage. Conversely, if the first voltage amplitude is lower than the second voltage amplitude, the first bus voltage is determined as the bus voltage to be adjusted, and the second bus voltage is determined as the reference bus voltage.

[0027] Furthermore, the first supply voltage or the second supply voltage corresponding to the bus voltage to be adjusted is determined as the voltage to be compensated; here, if the bus voltage to be adjusted is the first bus voltage, then the first supply voltage that generates the first bus voltage is determined as the voltage to be compensated; conversely, if the bus voltage to be adjusted is the second bus voltage, then the second supply voltage that generates the second bus voltage is determined as the voltage to be compensated.

[0028] Furthermore, the difference between the voltage amplitude of the reference bus voltage and the voltage amplitude of the bus voltage to be adjusted is determined as the target voltage amplitude in the target voltage parameter. For example, if the first bus voltage is the bus voltage to be adjusted and the second bus voltage is the reference bus voltage, then the difference between the second voltage amplitude and the first voltage amplitude is used as the target voltage amplitude in the target voltage parameter. Conversely, if the second bus voltage is the bus voltage to be adjusted and the first bus voltage is the reference bus voltage, then the difference between the first voltage amplitude and the second voltage amplitude is used as the target voltage amplitude in the target voltage parameter.

[0029] Furthermore, the phase difference between the voltage phase of the bus voltage to be adjusted and the voltage phase of the reference bus voltage is determined, and twice the value of the phase difference is determined as the phase adjustment amount; specifically, the voltage phase of the bus voltage to be adjusted can be subtracted from the voltage phase of the reference bus voltage, and the absolute value of the difference can be determined as the phase difference, and the phase difference value can be multiplied by two to obtain the phase adjustment amount.

[0030] As an example, if the first bus voltage is the bus voltage to be adjusted and the second bus voltage is the reference bus voltage, then the absolute value of the difference between the first voltage phase of the first bus voltage and the second voltage phase of the second bus voltage is determined as the phase difference; conversely, if the second bus voltage is the bus voltage to be adjusted and the first bus voltage is the reference bus voltage, then the absolute value of the difference between the second voltage phase of the second bus voltage and the first voltage phase of the first bus voltage is determined as the phase difference.

[0031] Furthermore, when the voltage phase of the bus voltage to be adjusted leads the voltage phase of the reference bus voltage, the phase adjustment amount is subtracted from the voltage phase of the bus voltage to be adjusted to obtain the target voltage phase in the target voltage parameters. For example, if the first bus voltage is the bus voltage to be adjusted and the second bus voltage is the reference bus voltage, the phase adjustment amount is subtracted from the first voltage phase of the first bus voltage to obtain the target voltage phase in the target voltage parameters. Conversely, if the second bus voltage is the bus voltage to be adjusted and the first bus voltage is the reference bus voltage, the phase adjustment amount is subtracted from the second voltage phase of the second bus voltage to obtain the target voltage phase in the target voltage parameters.

[0032] Furthermore, when the voltage phase of the bus voltage to be adjusted lags behind the voltage phase of the reference bus voltage, the voltage phase of the bus voltage to be adjusted is added to the phase adjustment amount to obtain the target voltage phase in the target voltage parameters. For example, if the first bus voltage is the bus voltage to be adjusted and the second bus voltage is the reference bus voltage, then the first voltage phase of the first bus voltage is added to the phase adjustment amount to obtain the target voltage phase in the target voltage parameters; conversely, if the second bus voltage is the bus voltage to be adjusted and the first bus voltage is the reference bus voltage, then the second voltage phase of the second bus voltage is added to the phase adjustment amount to obtain the target voltage phase in the target voltage parameters.

[0033] Then, the series voltage compensation unit 100 is controlled to generate the compensation voltage having the target voltage parameters, and voltage compensation is performed on the voltage to be compensated based on the compensation voltage; Specifically, the loop controller 300 can control the series voltage compensation unit 100 to generate the compensation voltage, wherein the voltage amplitude of the compensation voltage is the target voltage amplitude, and the voltage phase of the compensation voltage is the target voltage phase; further, the compensation voltage is superimposed on the voltage to be compensated to perform voltage compensation on the voltage to be compensated. Specifically, the compensation voltage and the voltage to be compensated are vector superimposed, and the vector formed by the superposition cancels out the amplitude deviation and phase deviation between the voltage to be compensated and the other low-voltage bus voltage, thus completing the real-time dynamic voltage compensation processing of the voltage to be compensated.

[0034] Finally, the loop-closing controller 300 can control the switching unit 200 to conduct a loop-closing operation on the first low-voltage bus L1 and the second low-voltage bus L2. Specifically, the loop-closing controller 300 can monitor the voltage parameters of the first bus voltage and the second bus voltage in real time, and when the voltage amplitude of the first bus voltage is the same as that of the second bus voltage, and the voltage phase of the first bus voltage is the same as that of the second bus voltage, the controller controls the switching unit 200 to conduct, so as to realize the loop closure between the low-voltage section where the first low-voltage bus L1 is located and the low-voltage section where the second low-voltage bus L2 is located.

[0035] The low-voltage distribution substation interconnection loop closing device provided in this embodiment collects the actual voltage parameters of two low-voltage busbars in real time, selects the voltage to be compensated based on the actual voltage difference between the low-voltage busbars, and performs voltage compensation accordingly. This eliminates the voltage deviation between the two busbars. It avoids misjudgment of loop closing conditions caused by relying solely on the transformer outlet voltage, suppresses the inrush circulating current generated during closing, effectively reduces the probability of equipment damage, and significantly improves the reliability and safety of the distribution substation interconnection loop closing operation.

[0036] In an optional embodiment, such as Figure 2 As shown, the series voltage compensation unit includes a first series voltage compensation unit 110 and a second series voltage compensation unit 120. Specifically, the input terminal of the first series voltage compensation unit 110 is connected to the low-voltage winding of the first transformer T1, and the output terminal of the first series voltage compensation unit 110 is connected to the first low-voltage bus L1. Further, the input terminal of the second series voltage compensation unit 120 is connected to the low-voltage winding of the second transformer T2, and the output terminal of the second series voltage compensation unit 120 is connected to the second low-voltage bus L2. Furthermore, the output terminal of the loop-closing controller 300 is connected to the control terminals of the first series voltage compensation unit 110 and the second series voltage compensation unit 120, respectively. When the first supply voltage is the voltage to be compensated, the loop-closing controller 300 controls the first series voltage compensation unit 110 to generate the compensation voltage and performs voltage compensation on the first supply voltage flowing through the first series voltage compensation unit 110. Conversely, when the second supply voltage is the voltage to be compensated, the loop-closing controller 300 controls the second series voltage compensation unit 120 to generate the compensation voltage and performs voltage compensation on the second supply voltage flowing through the second series voltage compensation unit 120. The embodiments provided in this application can perform voltage compensation on the first supply voltage and the second supply voltage based on the first series voltage compensation unit and the second series voltage compensation unit, respectively, improving the flexibility of voltage compensation.

[0037] In an optional embodiment, the first series voltage compensation unit includes a first inverter and a first series coupling transformer; specifically, the DC input terminal of the first inverter is connected to an external DC power supply to obtain a DC voltage; the control terminal of the first inverter is connected to the output terminal of the loop controller; the AC output terminal of the first inverter is connected to the first primary winding of the first series coupling transformer; the first secondary winding of the first series coupling transformer is connected in series between the first transformer and the first low-voltage bus; and the first supply voltage is sent to the first low-voltage bus via the first secondary winding. Furthermore, the loop-closed controller is used to control the first inverter to generate the compensation voltage when the first supply voltage is the voltage to be compensated, and to apply the compensation voltage to the first primary winding, so that the compensation voltage is superimposed on the voltage to be compensated on the branch where the first secondary winding is located, so as to perform voltage compensation on the voltage to be compensated. Here, the first inverter can be a sinusoidal pulse width modulation (SPWM) inverter, which includes multiple power switching devices. The loop-closed controller can output a pulse width modulation signal to the power switching devices of the SPWM inverter, adjust the output voltage amplitude by changing the amplitude of the modulation wave, and adjust the output voltage phase by changing the start trigger time of the modulation wave, thereby precisely controlling the first inverter to output a compensation voltage with specified amplitude and phase parameters.

[0038] Similarly, the second series voltage compensation unit includes a second inverter and a second series coupling transformer; specifically, the DC input terminal of the second inverter is connected to an external DC power supply to obtain DC voltage, the control terminal of the second inverter is connected to the output terminal of the closed-loop controller, the AC output terminal of the second inverter is connected to the second primary winding of the second series coupling transformer, the second secondary winding of the second series coupling transformer is connected in series between the second transformer and the second low-voltage bus, and the second supply voltage is sent to the second low-voltage bus via the second secondary winding; Furthermore, the loop-closed controller is used to control the second inverter to generate the compensation voltage when the second supply voltage is the voltage to be compensated, and to apply the compensation voltage to the second primary winding, so that the compensation voltage is superimposed on the voltage to be compensated on the branch where the second secondary winding is located, so as to perform voltage compensation on the voltage to be compensated. Here, the second inverter can also be a sinusoidal pulse width modulation inverter, which is equipped with multiple power switching devices; the loop-closed controller can send a pulse width modulation signal with a specific duty cycle to the power switching devices of the SPWM inverter, change the output voltage amplitude by adjusting the modulation wave amplitude, and change the output voltage phase by adjusting the trigger time of the modulation wave, thereby precisely controlling the second inverter to output a compensation voltage whose amplitude and phase both conform to the set values.

[0039] The embodiments provided in this application can select the corresponding compensation unit to engage voltage compensation based on the voltage difference between the two sides, flexibly generate the specified compensation voltage with the help of the inverter, and quickly synchronize the voltages on both sides through series superposition of the coupling transformer, so as to effectively suppress the loop current and improve the reliability of the interconnection closing of the transformer area.

[0040] In an optional embodiment, such as Figure 3 As shown, the switching unit includes a first switch S1 and a second switch S2. Specifically, the first end of the first switch S1 is connected between the first low-voltage bus L1 and the first series voltage compensation unit 110, the second end of the first switch S1 is connected to the first end of the second switch S2, and the second end of the second switch S2 is connected between the second low-voltage bus L2 and the second series voltage compensation unit 120. Here, the control terminal of the loop controller is connected to the control terminals of the first switch S1 and the second switch S2 respectively to control the on / off state of the first switch S1 and the second switch S2.

[0041] Furthermore, such as Figure 3As shown, the loop-closing device for the low-voltage distribution substation also includes a rectifier unit 400. Here, the AC side connection terminal of the rectifier unit 400 is connected between the first switch S1 and the second switch S2. The rectifier unit 400 is used to obtain electrical energy from the first low-voltage bus L1 or the second low-voltage bus L2 and to supply power to the first series voltage compensation unit 110 and the second series voltage compensation unit 120. When voltage compensation is required for the first low-voltage bus L1 and its corresponding first supply voltage, the loop-closing controller 300 can control the first switch S1 to open and the second switch S2 to open, allowing the rectifier unit 400 to obtain electrical energy from the second low-voltage bus L2 to supply power to the first series voltage compensation unit 110. Conversely, when voltage compensation is required for the second low-voltage bus L2 and its corresponding second supply voltage, the loop-closing controller 300 can control the first switch S1 to open and the second switch S2 to open, allowing the rectifier unit 400 to obtain electrical energy from the first low-voltage bus L1 to supply power to the second series voltage compensation unit 120.

[0042] Furthermore, the rectifier unit 400 includes a transformer unit T3 and a rectifier RE; specifically, the low-voltage side winding of the transformer unit T3 is connected between the first switch S1 and the second switch S2, and the high-voltage side winding of the transformer unit is connected to the AC input terminal of the rectifier RE. The transformer unit T3 is used to obtain AC power supply voltage from the first low-voltage bus L1 or the second low-voltage bus L2, and to step up the AC power supply voltage before sending the stepped-up AC power supply voltage to the rectifier RE. Furthermore, the DC terminal of the rectifier RE is connected to the power supply terminals of the first series voltage compensation unit 110 and the second series voltage compensation unit 120, for converting the AC supply voltage into a DC supply voltage, so as to supply power to the first series voltage compensation unit 110 and the second series voltage compensation unit 120 based on the DC supply voltage. The embodiments provided in this application can obtain electrical energy from a low-voltage distribution area and supply power to the first series voltage compensation unit or the second series voltage compensation unit, thereby improving the power supply stability of the device.

[0043] Furthermore, the first supply voltage is a three-phase supply voltage, including a first phase A supply voltage, a first phase B supply voltage, and a first phase C supply voltage; furthermore, as... Figure 4As shown, the first A-phase terminal of the first transformer T1 is connected to the first A-phase bus of the first low-voltage bus L1 via the first series voltage compensation unit 110 to output the first A-phase power supply voltage to the first A-phase bus; the first B-phase terminal of the first transformer T1 is connected to the first B-phase bus of the first low-voltage bus L1 via the first series voltage compensation unit 110 to output the first B-phase power supply voltage to the first B-phase bus; the first C-phase terminal of the first transformer T1 is connected to the first C-phase bus of the first low-voltage bus L1 via the first series voltage compensation unit 110 to output the first C-phase power supply voltage to the first C-phase bus; furthermore, the first neutral line terminal of the first transformer T1 is connected to the first neutral line bus of the first low-voltage bus L1 via the first series voltage compensation unit 110.

[0044] Furthermore, the second power supply voltage is a three-phase power supply voltage, including a second A-phase power supply voltage, a second B-phase power supply voltage, and a second C-phase power supply voltage. Specifically, the second A-phase terminal of the second transformer T2 is connected to the second A-phase bus of the second low-voltage bus L2 via the second series voltage compensation unit 120 to output the second A-phase power supply voltage to the second A-phase bus. Furthermore, the second B-phase terminal of the second transformer T2 is connected to the second B-phase bus of the second low-voltage bus L2 via the second series voltage compensation unit 120 to output the second B-phase power supply voltage to the second B-phase bus. Furthermore, the second C-phase terminal of the second transformer T2 is connected to the second C-phase bus of the second low-voltage bus via the second series voltage compensation unit 120 to output the second C-phase power supply voltage to the second C-phase bus. Furthermore, the second neutral line terminal of the second transformer T2 is connected to the second neutral line bus of the second low-voltage bus L2 via the second series voltage compensation unit 120.

[0045] Furthermore, the first series voltage compensation unit 110 includes a third inverter 111, a fourth inverter 112, a fifth inverter 113, a third series coupling transformer 114, a fourth series coupling transformer 115, and a fifth series coupling transformer 116. Specifically, the DC terminals of the third inverter 111, the fourth inverter 112, and the fifth inverter 113 are connected to the DC terminal of the rectifier RE to obtain DC power; the AC terminal of the third inverter 111 is connected to the third primary winding of the third series-coupled transformer 114, the AC terminal of the fourth inverter 112 is connected to the fourth primary winding of the fourth series-coupled transformer 115, and the AC terminal of the fifth inverter 113 is connected to the fifth primary winding of the fifth series-coupled transformer 116. Furthermore, the loop-closed controller (not shown in the figure) is connected to the third inverter 111, the fourth inverter 112, and the fifth inverter 113, and is used to control the third inverter 111 to output the A-phase compensation voltage to the third primary winding, control the fourth inverter 112 to output the B-phase compensation voltage to the fourth primary winding, and control the fifth inverter 113 to output the C-phase compensation voltage to the fifth primary winding. Here, when the first supply voltage is the voltage to be compensated, the loop-closed controller can control the third inverter 111, the fourth inverter 112, and the fifth inverter 113 to output the A-phase compensation voltage, the B-phase compensation voltage, and the C-phase compensation voltage, respectively.

[0046] Furthermore, the first A-phase terminal of the first transformer T1 is connected to the first A-phase bus of the first low-voltage bus L1 via the third secondary winding of the third series coupling transformer 114. The third series coupling transformer 114 is used to apply the A-phase compensation voltage at the third primary winding to the third secondary winding to compensate the first A-phase supply voltage. Furthermore, the first B-phase terminal of the first transformer T1 is connected to the first B-phase bus of the first low-voltage bus L1 via the fourth secondary winding of the fourth series coupling transformer 115. The fourth series coupling transformer 115 is used to apply the B-phase compensation voltage at the fourth primary winding to the fourth secondary winding to compensate the first B-phase power supply voltage. Furthermore, the first C-phase terminal of the first transformer T1 is connected to the first C-phase bus of the first low-voltage bus L1 via the fifth secondary winding of the fifth series coupling transformer 116. The fifth series coupling transformer is used to apply the C-phase compensation voltage at the fifth primary winding to the fifth secondary winding to compensate the first C-phase power supply voltage.

[0047] Furthermore, the second series voltage compensation unit 120 includes a sixth inverter 121, a seventh inverter 122, an eighth inverter 123, a sixth series coupling transformer 124, a seventh series coupling transformer 125, and an eighth series coupling transformer 126. Specifically, the DC terminals of the sixth inverter 121, the seventh inverter 122, and the eighth inverter 123 are connected to the DC terminal of the rectifier RE to obtain DC power supply; the AC terminal of the sixth inverter 121 is connected to the sixth primary winding of the sixth series-coupled transformer 124, the AC terminal of the seventh inverter 122 is connected to the seventh primary winding of the seventh series-coupled transformer 125, and the AC terminal of the eighth inverter 123 is connected to the eighth primary winding of the eighth series-coupled transformer 126. Furthermore, the loop controller (not shown in the figure) is connected to the sixth inverter 121, the seventh inverter 122, and the eighth inverter 123, and is used to control the sixth inverter 121 to output the A-phase compensation voltage to the sixth primary winding, control the seventh inverter 122 to output the B-phase compensation voltage to the seventh primary winding, and control the eighth inverter 123 to output the C-phase compensation voltage to the eighth primary winding. Here, when the second supply voltage is the voltage to be compensated, the loop controller can control the sixth inverter 121, the seventh inverter 122, and the eighth inverter 123 to output the A-phase compensation voltage, the B-phase compensation voltage, and the C-phase compensation voltage, respectively.

[0048] Furthermore, the second A-phase terminal of the second transformer T2 is connected to the second A-phase bus of the second low-voltage bus L2 via the sixth secondary winding of the sixth series coupling transformer 124. The sixth series coupling transformer 124 is used to apply the A-phase compensation voltage at the sixth primary winding to the sixth secondary winding to compensate the second A-phase supply voltage. Furthermore, the second B-phase terminal of the second transformer T2 is connected to the second B-phase bus of the second low-voltage bus via the seventh secondary winding of the seventh series coupling transformer 125. The seventh series coupling transformer 125 is used to apply the B-phase compensation voltage at the seventh secondary winding to the seventh secondary winding to compensate the second B-phase power supply voltage. Furthermore, the second C-phase terminal of the second transformer T2 is connected to the second C-phase bus of the second low-voltage bus L2 via the eighth secondary winding of the eighth series coupling transformer 126. The eighth series coupling transformer 126 is used to apply the C-phase compensation voltage at the eighth primary winding to the eighth secondary winding to compensate the second C-phase power supply voltage.

[0049] Furthermore, the first switch S1 has three sub-switches that are linked together to turn on and off. The second switch S2 also has three sub-switches that are linked together to turn on and off. The first sub-switch of the first switch S1 and the first sub-switch of the second switch S2 are connected in series between the first phase A bus and the second phase A bus. The second sub-switch of the first switch S1 and the second sub-switch of the second switch S2 are connected in series between the first phase B bus and the second phase B bus. The third sub-switch of the first switch S1 and the third sub-switch of the second switch S2 are connected in series between the first phase C bus and the second phase C bus. The first neutral bus and the second neutral bus are connected. This allows the loop closing controller to control the first low-voltage bus L1 and the second low-voltage bus L2 to close the loop.

[0050] The serial numbers in this application are for descriptive purposes only and do not represent the superiority or inferiority of any particular implementation scenario. The above disclosures are merely a few specific implementation scenarios of this application; however, this application is not limited thereto, and any variations conceived by those skilled in the art should fall within the protection scope of this application.

Claims

1. A communication loop closing device for a low-voltage distribution radio area, characterized in that, The device includes a series voltage compensation unit, a switching unit, and a loop controller. The first input terminal of the series voltage compensation unit is connected to an external first transformer, and the first output terminal of the series voltage compensation unit is connected to a first low-voltage bus to receive a first power supply voltage from the first transformer and supply power to the first low-voltage bus. The second input terminal of the series voltage compensation unit is connected to the external second transformer, and the second output terminal of the series voltage compensation unit is connected to the second low-voltage bus to receive the second power supply voltage from the second transformer and supply power to the second low-voltage bus. The switching unit is connected in series between the first low-voltage bus and the second low-voltage bus, and the loop controller is connected to the series voltage compensation unit and the switching unit respectively. The loop closing controller is configured to perform the following processes: The loop controller determines the voltage parameters of the first bus voltage at the first low-voltage bus and the voltage parameters of the second bus voltage at the second low-voltage bus. Based on the parameter deviation between the voltage parameters of the first bus voltage and the voltage parameters of the second bus voltage, the voltage to be compensated is determined between the first supply voltage and the second supply voltage, and the target voltage parameter of the compensation voltage is determined. The series voltage compensation unit is controlled to generate the compensation voltage having the target voltage parameters, and voltage compensation is performed on the voltage to be compensated based on the compensation voltage; The switching unit is controlled to turn on in order to perform a loop-closing operation on the first low-voltage bus and the second low-voltage bus.

2. The low-voltage distribution transformer area interconnection and loop-closing device according to claim 1, characterized in that, The high-voltage side of the first transformer is connected to the external first high-voltage bus, and the low-voltage side of the first transformer is connected to the first access terminal of the series voltage compensation unit. The high-voltage side of the second transformer is connected to the external second high-voltage bus, and the low-voltage side of the second transformer is connected to the second access terminal of the series voltage compensation unit.

3. The low-voltage distribution transformer area interconnection and loop-closing device according to claim 1, characterized in that, The voltage parameters include voltage amplitude and voltage phase; The loop controller, based on the parameter deviation between the voltage parameters of the first bus voltage and the second bus voltage, determines the voltage to be compensated from the first supply voltage and the second supply voltage, and determines the target voltage parameters of the compensation voltage, including: The loop controller determines the bus voltage with the lower voltage amplitude between the first bus voltage and the second bus voltage as the bus voltage to be adjusted, and determines the bus voltage with the higher voltage amplitude as the reference bus voltage. The first or second supply voltage corresponding to the bus voltage to be adjusted is determined as the voltage to be compensated. The difference between the voltage amplitude of the reference bus voltage and the voltage amplitude of the bus voltage to be adjusted is determined as the target voltage amplitude in the target voltage parameter; Determine the phase difference between the voltage phase of the bus voltage to be adjusted and the voltage phase of the reference bus voltage, and determine twice the value of the phase difference as the phase adjustment amount; When the voltage phase of the bus voltage to be adjusted leads the voltage phase of the reference bus voltage, the phase adjustment amount is subtracted from the voltage phase of the bus voltage to be adjusted to obtain the target voltage phase in the target voltage parameters. When the voltage phase of the bus voltage to be adjusted lags behind the voltage phase of the reference bus voltage, the voltage phase of the bus voltage to be adjusted is added to the phase adjustment amount to obtain the target voltage phase in the target voltage parameters.

4. The low-voltage distribution transformer area connection and closing device according to claim 3, characterized in that, The loop controller controls the series voltage compensation unit to generate the compensation voltage having the target voltage parameters, and performs voltage compensation on the voltage to be compensated based on the compensation voltage, including: The loop controller controls the series voltage compensation unit to generate the compensation voltage, wherein the voltage amplitude of the compensation voltage is the target voltage amplitude, and the voltage phase of the compensation voltage is the target voltage phase; The compensation voltage is superimposed on the voltage to be compensated to perform voltage compensation on the voltage to be compensated.

5. The low-voltage distribution transformer area interconnection and loop-closing device according to claim 1, characterized in that, The series voltage compensation unit includes a first series voltage compensation unit and a second series voltage compensation unit. The input terminal of the first series voltage compensation unit is connected to the first transformer, and the output terminal of the first series voltage compensation unit is connected to the first low-voltage bus. The input terminal of the second series voltage compensation unit is connected to the second transformer, and the output terminal of the second series voltage compensation unit is connected to the second low-voltage bus. The output terminal of the loop controller is connected to the control terminal of the first series voltage compensation unit and the control terminal of the second series voltage compensation unit, respectively. When the first supply voltage is the voltage to be compensated, the loop controller is used to control the first series voltage compensation unit to generate the compensation voltage and to compensate the first supply voltage. When the second supply voltage is the voltage to be compensated, the loop controller is used to control the second series voltage compensation unit to generate the compensation voltage and to perform voltage compensation on the second supply voltage.

6. The low-voltage distribution transformer area interconnection and loop-closing device according to claim 5, characterized in that, The first series voltage compensation unit includes a first inverter and a first series coupling transformer; The DC input terminal of the first inverter is connected to an external DC power supply, the control terminal of the first inverter is connected to the output terminal of the loop controller, the AC output terminal of the first inverter is connected to the first primary winding of the first series-coupled transformer, and the first secondary winding of the first series-coupled transformer is connected in series between the first transformer and the first low-voltage bus. The closed-loop controller is used to control the first inverter to generate the compensation voltage when the first supply voltage is the voltage to be compensated, and to apply the compensation voltage to the first primary winding so that the compensation voltage is superimposed on the voltage to be compensated on the branch where the first secondary winding is located, so as to perform voltage compensation on the voltage to be compensated.

7. The low-voltage distribution transformer area interconnection and loop-closing device according to claim 5, characterized in that, The second series voltage compensation unit includes a second inverter and a second series coupling transformer; The DC input terminal of the second inverter is connected to an external DC power supply, the control terminal of the second inverter is connected to the output terminal of the loop controller, the AC output terminal of the second inverter is connected to the second primary winding of the second series-coupled transformer, and the second secondary winding of the second series-coupled transformer is connected in series between the second transformer and the second low-voltage bus. The closed-loop controller is used to control the second inverter to generate the compensation voltage when the second supply voltage is the voltage to be compensated, and to apply the compensation voltage to the second primary winding so that the compensation voltage is superimposed on the voltage to be compensated on the branch where the second secondary winding is located, so as to perform voltage compensation on the voltage to be compensated.

8. The low-voltage distribution transformer area interconnection and loop-closing device according to claim 5, characterized in that, The switching unit includes a first switch and a second switch; The first end of the first switch is connected to the first low-voltage busbar, the second end of the first switch is connected to the first end of the second switch, and the second end of the second switch is connected to the second low-voltage busbar. The control terminal of the loop controller is connected to the control terminal of the first switch and the control terminal of the second switch respectively, so as to control the on / off state of the first switch and the second switch.

9. The low-voltage distribution transformer area interconnection and loop-closing device according to claim 8, characterized in that, The communication loop closing device of the low-voltage distribution radio area also includes a rectifier unit; The AC side of the rectifier unit is connected between the first switch and the second switch. The rectifier unit is used to obtain electrical energy from the first low-voltage bus or the second low-voltage bus and to supply power to the first series voltage compensation unit and the second series voltage compensation unit.

10. The low-voltage distribution transformer area interconnection and loop-closing device according to claim 9, characterized in that, The rectification unit includes a transformer unit and a rectifier; The low-voltage side of the transformer unit is connected between the first switch and the second switch, and the high-voltage side of the transformer unit is connected to the AC input terminal of the rectifier. The transformer unit is used to obtain AC power supply voltage from the first low-voltage bus or the second low-voltage bus, step up the AC power supply voltage, and send the step-up AC power supply voltage to the rectifier. The DC terminal of the rectifier is connected to the power supply terminals of the first series voltage compensation unit and the second series voltage compensation unit, and is used to convert the AC power supply voltage into a DC power supply voltage to supply power to the first series voltage compensation unit and the second series voltage compensation unit based on the DC power supply voltage.

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