A multifunctional electric section switch for a substation and a control method thereof

Abstract

The application provides a multifunctional electric section switch for a transformer substation and a control method thereof, comprising a back-to-back three-phase full-bridge AC / AC converter and a parallel switch; voltage output ends of the three-phase full-bridge AC / AC converter are respectively connected with filter inductors and the parallel switch; the parallel switch comprises a plurality of anti-parallel controllable high-frequency switches; the three-phase full-bridge AC / AC converter comprises a plurality of anti-parallel diode controllable high-frequency switches; and the technical scheme can effectively solve the problem of long-time power failure of the electric equipment of the transformer substation caused by instantaneous faults.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sectionalizing switch, in particular to a multifunctional electric sectionalizing switch for transformer substation and a control method thereof. BACKGROUND

[0002] At present, the sectionalizing switch used in the power system of transformer substation is a traditional molded case circuit breaker. The molded case circuit breaker can only realize simple manual opening and closing function, and cannot realize automatic phase checking and automatic switching of standby power. When the operation mode of the power system of transformer substation needs to be adjusted from the split mode to the parallel mode, according to the "Operation Management Regulations of Transformer Substation", the operating personnel need to first disconnect the incoming line power switch of the parallel AC bus, and then close the sectionalizing switch after confirming that the bus has no voltage. The purpose of this operation is to prevent the voltage difference and phase difference between the two sections of AC bus, so as to avoid the phenomenon of non-synchronous closing. However, this operation will cause the short-time voltage loss of the parallel AC bus, thereby causing the power failure of the AC power equipment in the transformer substation and the inability to work. At the same time, the sectionalizing switch used in the transformer substation does not have the fault detection automatic switching function, and cannot realize the automatic detection and switching function of the sectionalizing switch due to the fault voltage loss of the bus, thereby causing the power failure of the power equipment in the transformer substation.

[0003] The disadvantages of the prior art are as follows:

[0004] Single function. At present, the sectionalizing switch used in the power system of transformer substation is a traditional molded case circuit breaker. The molded case circuit breaker can only realize simple manual opening and closing function, and cannot realize automatic phase checking and automatic switching of standby power.

[0005] Limited operation mode. When the operation mode of the power system of transformer substation needs to be adjusted from the split mode to the parallel mode, according to the "Operation Management Regulations of Transformer Substation", the operating personnel need to first disconnect the incoming line power switch of the parallel AC bus, and then close the sectionalizing switch after confirming that the bus has no voltage. This operation will cause the short-time voltage loss of the parallel AC bus, thereby causing the power failure of the AC power equipment in the transformer substation and the inability to work. SUMMARY

[0006] Therefore, the present application aims to provide a multifunctional electric sectionalizing switch for transformer substation and a control method thereof, which effectively solves the problem of long-time power failure of the power equipment in the transformer substation caused by transient faults.

[0007] To achieve the above object, the application adopts the following technical scheme: a multifunctional electric section switch for a substation, comprising a back-to-back three-phase full-bridge AC / AC converter and a parallel switch; voltage output ends of the three-phase full-bridge AC / AC converter are respectively connected with filter inductors and the parallel switch; the parallel switch comprises a first anti-parallel controllable high-frequency switch V1, a second anti-parallel controllable high-frequency switch V2 and a third anti-parallel controllable high-frequency switch V3; the three-phase full-bridge AC / AC converter comprises a first anti-parallel diode controllable high-frequency switch T a1 , a second anti-parallel diode controllable high-frequency switch T a2 , a third anti-parallel diode controllable high-frequency switch T b1 , a fourth anti-parallel diode controllable high-frequency switch T b2 , a fifth anti-parallel diode controllable high-frequency switch T c1 , a sixth anti-parallel diode controllable high-frequency switch T c2 , a seventh anti-parallel diode controllable high-frequency switch T a3 , an eighth anti-parallel diode controllable high-frequency switch T a4 , a ninth anti-parallel diode controllable high-frequency switch T b3 , a tenth anti-parallel diode controllable high-frequency switch T b4 , an eleventh anti-parallel diode controllable high-frequency switch T c3 , and a twelfth anti-parallel diode controllable high-frequency switch T c4 .

[0008] The first anti-parallel diode controllable high-frequency switch T a1 and the second anti-parallel diode controllable high-frequency switch T a2 , the third anti-parallel diode controllable high-frequency switch T b1 and the fourth anti-parallel diode controllable high-frequency switch T b2 , the fifth anti-parallel diode controllable high-frequency switch T c1 and the sixth anti-parallel diode controllable high-frequency switch T c2 are respectively connected with a first segment ABC three-phase bus;

[0009] The seventh anti-parallel diode controllable high-frequency switch T a3 and the eighth anti-parallel diode controllable high-frequency switch T a4 , the ninth anti-parallel diode controllable high-frequency switch T b3 and the tenth anti-parallel diode controllable high-frequency switch T b4 , the eleventh anti-parallel diode controllable high-frequency switch T c3 and the twelfth anti-parallel diode controllable high-frequency switch T c4 are respectively connected with a second segment ABC three-phase bus.

[0010] In a preferred embodiment, the operating principle is as follows:

[0011] (1) When busbars I and II are in separate operation, T ak T bk T ck Controllable high-frequency switches V1, V2, and V3 are in the off state, where k = 1, 2, 3, and 4; the entire segmented switch is in the non-operating state.

[0012] (2) When the DC bus sections I and II need to operate in parallel, the controller compares the voltage U of the DC bus section II. IIA U IIB U IIC and the output voltage U of the three-phase full-bridge AC / AC converter OA U OB U OC The phase and amplitude of the two values ​​are only considered when the difference between their phase and amplitude is less than the controller setpoint δ. set and U set Only when the time is right will the parallel switch be allowed to conduct, ultimately achieving parallel operation of DC buses I and II, where δ set and U set These are the maximum phase difference and amplitude difference allowed for the two bus segments to operate in parallel, as set by the controller.

[0013] This invention also provides a control method for a power sectionalizing switch used in a multifunctional substation, which employs the aforementioned power sectionalizing switch for a multifunctional substation. The specific steps are as follows:

[0014] When parallel operation is required, the controller acquires the voltage U of the second-section bus. IIA U IIB U IIC and the output voltage U of the three-phase full-bridge AC / AC converter OA U OB U OC Given the phase and amplitude, calculate the difference between them;

[0015] Phase difference

[0016] Δδ=|δ IIN -δ ON | (1)

[0017] In the formula δ IIN and δ ON These represent the phases of the three-phase voltages of the II section bus and the three-phase voltages of the converter output, respectively, N = A, B, C; amplitude difference.

[0018] ΔU=|U IIN -U ON | (2)

[0019] In the formula UIIN and U ON These are the amplitudes of the three-phase voltage of the II section bus and the three-phase voltage output of the converter, respectively, N = A, B, C;

[0020] When Δδ>δ set And ΔU>U set At this time, the controller continues to send disconnect commands to the parallel switches V1, V2, and V3, and the DC bus sections I and II operate separately at any point; at this time, the controller needs to continue to adjust to reduce Δδ and ΔU.

[0021] When Δδ>δ set And ΔU < U set At this time, the controller continues to send disconnect commands to the parallel switches V1, V2, and V3, and the DC bus sections I and II operate separately at any point; at this time, the controller needs to continue to adjust to make Δδ smaller;

[0022] When Δδ < δ set And ΔU>U set At this time, the controller continues to send disconnect commands to the parallel switches V1, V2, and V3, and the DC bus sections I and II operate separately at any point; at this time, the controller needs to continue to adjust to make ΔU smaller;

[0023] When Δδ < δ set And ΔU < U set At this time, the controller sends a conduction command to the parallel switches V1, V2, and V3, and the DC buses of section I and section II operate in parallel.

[0024] In a preferred embodiment, when the molded case switch of bus section I trips due to a short-circuit fault, the controller detects the voltage U of bus section I. IA U IB U IC The value; when the bus voltage is less than the unloaded set value:

[0025]

[0026] In the formula U WY The no-pressure setpoint for the controller;

[0027] At this time, the controller determines that the I-section busbar is undervoltage and injects a small 5th harmonic current I into the three phases (A, B, and C) of the I-section busbar. 5A I 5B I 5C Simultaneously, the 5th harmonic voltage value U generated on bus section I was collected. 5A U 5B U 5C ;

[0028]

[0029] In the formula Z A ZB Z C The controller calculates the three-phase impedance of bus section I using the 5th harmonic signal;

[0030] When Z A Z B Z C All are greater than the impedance setpoint Z of the controller. set If the fault occurs, the controller considers bus section I to be a transient short-circuit fault; otherwise, it considers bus section I to be a permanent short-circuit fault.

[0031] Transient fault criteria

[0032]

[0033] Permanent Fault Criteria

[0034] Z A ≤Z set or Z B ≤Z set or Z C ≤Z set (6)

[0035] When the controller determines that the fault on bus section I is a transient fault, the controller will close the sectionalizing switch after a 5-second delay to ensure normal power supply to the electrical equipment on bus section I of the substation; when the controller determines that the fault on bus section I is a permanent fault, the controller will not take any action.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] (1) Research a multi-functional substation power sectionalizing switch. The sectionalizing switch adopts a back-to-back three-phase full-bridge AC / AC topology and solves the problem that existing sectionalizing switches cannot meet the asynchronous parallel connection of two AC bus sections by means of voltage tracking.

[0038] (2) An impedance method involving the injection of a high-frequency small signal was proposed to achieve fault type assessment. When the fault is assessed as transient, the controller activates the automatic transfer switch and closes the sectionalizing switch to ensure normal power supply to the AC loads in the substation. When the fault is assessed as permanent, the controller disables the automatic transfer switch. This effectively solves the problem of prolonged power outage of substation equipment caused by transient faults. Attached Figure Description

[0039] Figure 1 This is a topology diagram of a segmented switch according to a preferred embodiment of the present invention;

[0040] Figure 2 This is a schematic diagram of the automatic switchover control principle for fault assessment according to a preferred embodiment of the present invention. Detailed Implementation

[0041] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0042] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, 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 application pertains.

[0043] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this application; as used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise; furthermore, it should be understood that when the terms “comprising” and / or “including” are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0044] A multifunctional substation power sectionalizing switch consists of a back-to-back three-phase full-bridge AC / AC converter and a parallel switch. By employing voltage tracking, it solves the problem that existing sectionalizing switches cannot meet the asynchronous parallel connection requirements of two AC bus sections. Simultaneously, by using an impedance method with injected high-frequency small signals, it enables fault type analysis, resolving the issue of prolonged power outages of substation equipment caused by transient faults. Figure 1 It is a segmented switch topology.

[0045] Figure 1 Middle U IA U IB U IC U IIA U IIB U IIC These are the three-phase bus voltages (A, B, and C) of sections I and II of the power system, respectively; U OA U OB U OC V1 is the output voltage of the three-phase full-bridge AC / AC converter; L is the filter inductor; C is the voltage regulator capacitor; V1, V2, and V3 are anti-parallel controllable high-frequency switches; T is the output voltage of the three-phase full-bridge AC / AC converter. ak T bk T ck It is a high-frequency switch controlled by an anti-parallel diode, where k = 1, 2, 3, 4.

[0046] Operating mode and working principle

[0047] 1. When busbars I and II are in separate operation, T ak T bk T ck Controllable high-frequency switches V1, V2, and V3 are in the off state, where k = 1, 2, 3, and 4. The entire segmented switch is in a non-operating state.

[0048] 2. When DC bus sections I and II need to operate in parallel, the controller compares the voltage U of bus section II. IIA U IIB U IIC and the output voltage U of the three-phase full-bridge AC / AC converter OA U OB U OC The phase and amplitude of the two values ​​are only considered when the difference between their phase and amplitude is less than the controller setpoint δ. set and U set Only when the time is right will the parallel switch be allowed to conduct, ultimately achieving parallel operation of DC buses I and II, where δ set and U set These are the maximum phase difference and amplitude difference allowed for the two bus segments to operate in parallel, as set by the controller.

[0049] The specific steps are as follows:

[0050] When parallel operation is required, the controller acquires the voltage U of the second-section bus. IIA U IIB U IIC and the output voltage U of the three-phase full-bridge AC / AC converter OA U OB U OC Given the phase and amplitude, calculate the difference between them.

[0051] Phase difference

[0052] Δδ=|δ IIN -δ ON | (1)

[0053] In the formula δ IIN and δ ON The phases of the three-phase voltages of the II section bus and the three-phase voltages of the converter output are respectively, N = A, B, C.

[0054] Amplitude difference

[0055] ΔU=|U IIN -U ON | (2)

[0056] In the formula U IIN and U ON These are the amplitudes of the three-phase voltage of section II bus and the three-phase voltage output of the converter, respectively, where N = A, B, and C.

[0057] When Δδ>δ set And ΔU>U set At this time, the controller continues to send disconnect commands to the parallel switches V1, V2, and V3, and the DC buses of sections I and II operate separately. The controller then needs to continue adjusting to reduce Δδ and ΔU.

[0058] When Δδ>δ set And ΔU < U set At this time, the controller continues to send disconnect commands to the parallel switches V1, V2, and V3, and the DC buses of sections I and II operate separately. The controller then needs to continue adjusting to reduce Δδ.

[0059] When Δδ < δ set And ΔU>U set At this time, the controller continues to send disconnect commands to the parallel switches V1, V2, and V3, and the DC buses of sections I and II operate separately. The controller needs to continue adjusting to reduce ΔU.

[0060] When Δδ < δ set And ΔU < U set At this time, the controller sends a command to turn on the parallel switches V1, V2, and V3, and the DC buses of sections I and II operate in parallel.

[0061] The working principle of automatic transfer switch for fault diagnosis, and its control principle diagram, are as follows: Figure 2 As shown.

[0062] Figure 2 Middle U IA U IB U IC U IIA U IIB U IIC These are the three-phase bus voltages of sections I and II of the power system, respectively; I 5A I 5B I 5C A small 5th harmonic current is injected into the controller.

[0063] 1. When the molded case switch of bus section I trips due to a short circuit fault, the controller detects the voltage U of bus section I. IA U IB U IC The value. When all bus voltages are less than the unloaded set value:

[0064]

[0065] In the formula U WY The no-pressure setpoint for the controller.

[0066] At this time, the controller determines that the I-section busbar is undervoltage and injects a small 5th harmonic current I into the three phases (A, B, and C) of the I-section busbar. 5A I 5B I 5C Simultaneously, the 5th harmonic voltage value U generated on bus section I was collected. 5A U 5B U 5C .

[0067]

[0068] In the formula Z A Z B Z C The controller calculates the three-phase impedance of bus section I using the 5th harmonic signal.

[0069] When Z A Z B Z C All are greater than the impedance setpoint Z of the controller. set If the fault occurs, the controller considers bus section I to be experiencing a transient short-circuit fault. Otherwise, it considers bus section I to be experiencing a permanent short-circuit fault.

[0070] Transient fault criteria

[0071]

[0072] Permanent Fault Criteria

[0073] Z A ≤Z set or Z B ≤Z set or Z C ≤Z set (6)

[0074] When the controller determines that the fault on bus section I is a transient fault, the controller will close the sectionalizing switch after a 5-second delay to ensure normal power supply to the equipment on bus section I of the substation. When the controller determines that the fault on bus section I is a permanent fault, the controller will not take any action.

[0075] 2. When the I-section busbar needs to be de-energized for maintenance, the maintenance personnel should manually disconnect the molded case switch 1. At this time, the maintenance personnel need to disable the automatic transfer function of the fault assessment in the controller in advance, so that the sectionalizing switch does not have the automatic closing function.

[0076] Similarly, the same applies to busbar section II, which will not be elaborated upon here.

[0077] This sectionalizing switch adopts a back-to-back three-phase full-bridge AC / AC topology and utilizes voltage tracking to achieve asynchronous parallel operation of two AC bus sections. By injecting high-frequency small signals, the fault type of the bus is determined. When a transient fault is identified, the controller activates the automatic transfer switch (ATS) function to close the sectionalizing switch, ensuring normal power supply to the AC loads within the substation. When a permanent fault is identified, the controller disables the ATS function. This effectively solves the problem of prolonged power outages of substation equipment caused by transient faults.

Claims

1. A multi-functional substation power sectionalizing switch, characterized in that... The system includes a back-to-back three-phase full-bridge AC / AC converter and parallel switches; the voltage output terminals of the three-phase full-bridge AC / AC converter are respectively connected to filter inductors and then to the parallel switches; the parallel switches include a first anti-parallel controllable high-frequency switch V1, a second anti-parallel controllable high-frequency switch V2, and a third anti-parallel controllable high-frequency switch V3; the three-phase full-bridge AC / AC converter includes a first anti-parallel diode controllable high-frequency switch T. a1 The second anti-parallel diode controllable high-frequency switch T a2 The third anti-parallel diode controllable high-frequency switch T b1 The fourth anti-parallel diode controllable high-frequency switch T b2 Fifth anti-parallel diode controllable high-frequency switch T c1 The sixth anti-parallel diode controllable high-frequency switch T c2 The seventh anti-parallel diode controllable high-frequency switch T a3 Eighth anti-parallel diode controllable high-frequency switch T a4 Ninth anti-parallel diode controllable high-frequency switch T b3 10th Anti-parallel Diode Controlled High-Frequency Switch T b4 Eleventh anti-parallel diode controllable high-frequency switch T c3 The twelfth anti-parallel diode controllable high-frequency switch T c4 ; First anti-parallel diode controllable high-frequency switch T a1 and the second anti-parallel diode controllable high-frequency switch T a2 Between, the third anti-parallel diode controllable high-frequency switch T b1 and the fourth anti-parallel diode controllable high-frequency switch T b2 Between, the fifth anti-parallel diode controllable high-frequency switch T c1 And the sixth anti-parallel diode controllable high-frequency switch T c2 Each of the three phase busbars (A, B, and C) is connected to a separate section. The seventh anti-parallel diode controllable high-frequency switch T a3 And the eighth anti-parallel diode controllable high-frequency switch T a4 Between, the ninth anti-parallel diode controllable high-frequency switch T b3 And the tenth anti-parallel diode controllable high-frequency switch T b4 Between, the eleventh anti-parallel diode controllable high-frequency switch T c3 and the twelfth anti-parallel diode controllable high-frequency switch T c4 The two sections are connected to the three-phase busbars ABC of section II respectively.

2. The multi-functional substation power sectionalizing switch according to claim 1, characterized in that... The operating principle is as follows: (1) When busbars I and II are in separate operation, T ak T bk T ck Controllable high-frequency switches V1, V2, and V3 are in the off state, where k = 1, 2, 3, and 4; the entire segmented switch is in the non-operating state. (2) When the DC bus sections I and II need to operate in parallel, the controller compares the voltage U of the DC bus section II. IIA U IIB U IIC and the output voltage U of the three-phase full-bridge AC / AC converter OA U OB U OC The phase and amplitude of the signal are only considered when the difference between their phase and amplitude is less than the control setpoint δ. set and U set Only when the time is right will the parallel switch be allowed to conduct, ultimately achieving parallel operation of DC buses I and II, where δ set and U set These are the maximum phase difference and amplitude difference allowed for the two bus segments to operate in parallel, as set by the controller.

3. A control method for a power sectionalizing switch in a multi-functional substation, characterized in that... The following are the specific steps for using a multifunctional substation power sectionalizing switch as described in any one of claims 1 or 2: When parallel operation is required, the controller acquires the voltage U of the second-section bus. IIA U IIB U IIC and the output voltage U of the three-phase full-bridge AC / AC converter OA U OB U OC Given the phase and amplitude, calculate the difference between them; Phase difference Δδ=|δ IIN -d ON |(1) In the formula δ IIN and δ ON The phases of the three-phase voltage of the II section bus and the three-phase voltage of the converter output are respectively, N = A, B, C; Amplitude difference ΔU=|U IIN -U ON |(2) In the formula U IIN and U ON These are the amplitudes of the three-phase voltage of the II section bus and the three-phase voltage output of the converter, respectively, N = A, B, C; When Δδ>δ set And ΔU>U set At this time, the controller continues to send disconnect commands to the parallel switches V1, V2, and V3, and the DC bus sections I and II operate separately at any point; at this time, the controller needs to continue to adjust to reduce Δδ and ΔU. When Δδ>δ set And ΔU < U set At this time, the controller continues to send disconnect commands to the parallel switches V1, V2, and V3, and the DC bus sections I and II operate separately at any point; at this time, the controller needs to continue to adjust to make Δδ smaller; When Δδ < δ set And ΔU>U set At this time, the controller continues to send disconnect commands to the parallel switches V1, V2, and V3, and the DC bus sections I and II operate separately at any point; at this time, the controller needs to continue to adjust to make ΔU smaller; When Δδ < δ set And ΔU < U set At this time, the controller sends a conduction command to the parallel switches V1, V2, and V3, and the DC buses of section I and section II operate in parallel.

4. The control method for a multi-functional substation power sectionalizing switch according to claim 3, characterized in that, When the molded case switch of bus section I trips due to a short circuit fault, the controller detects the voltage U of bus section I. IA U IB U IC The value; when the bus voltage is less than the unloaded set value: In the formula U WY The no-pressure setpoint for the controller; At this time, the controller determines that the I-section busbar is undervoltage and injects a small 5th harmonic current I into the three phases (A, B, and C) of the I-section busbar. 5A I 5B I 5C Simultaneously, the 5th harmonic voltage value U generated on bus section I was collected. 5A U 5B U 5C ; In the formula Z A Z B Z C The controller calculates the three-phase impedance of bus section I using the 5th harmonic signal; When Z A Z B Z C All are greater than the impedance setpoint Z of the controller. set If the fault occurs, the controller considers bus section I to be a transient short-circuit fault; otherwise, it considers bus section I to be a permanent short-circuit fault. Transient fault criteria Permanent Fault Criteria When the controller determines that the fault on bus section I is a transient fault, the controller will close the sectionalizing switch after a 5-second delay to ensure normal power supply to the electrical equipment on bus section I of the substation; when the controller determines that the fault on bus section I is a permanent fault, the controller will not take any action.

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