A series compensation device

Abstract

The present application provides a series compensation device. The series compensation device includes a steel structure platform, a series compensation main equipment unit, and a high-frequency damping circuit. The two ends of the series compensation main equipment unit are respectively connected to the high-voltage busbar and low-voltage busbar of the series compensation device. The series compensation main equipment unit, the high-voltage busbar, and the low-voltage busbar are supported by at least two insulators fixed to the steel structure platform. The high-frequency damping circuit is connected between the low-voltage busbar and the steel structure platform, and the low-voltage busbar and the steel structure platform are connected only at one point through the high-frequency damping circuit.

Description

Technical Field

[0001] The present application relates to the technical field of flexible AC transmission systems (FACTS), and in particular to a series compensation device. Background Art

[0002] With economic development, the power load continues to grow, placing higher demands on the transmission capacity of the power grid. In particular, there is an increasing demand for power system flow control and voltage control, resulting in the increasing application of flexible AC transmission devices in power systems.

[0003] Structurally, flexible AC transmission devices can be divided into series, parallel and hybrid types. Figure 1 This is a schematic diagram of a series FACTO connected to a power system. Reference numerals 11 and 16 represent the busbars of the substations on either side, 12 and 15 represent the switches on either side of the line, 13 represents the transmission line, and 17 and 18 represent capacitor voltage transformers (CVTs) used to measure the line-to-ground voltage. Reference numeral 14 represents the series FACTO (also known as series compensation device), which includes fixed or thyristor-controlled series capacitor compensation devices (hereinafter referred to as series compensation), series resonant fault current limiters, distribution-type power flow controllers, and other FACTO devices. Its ground voltage is generally the transmission line voltage. Equipment-to-ground insulation requirements are high, so to reduce this level, the series FACTO is typically mounted on a steel platform. The steel platform is supported by support insulators and secured by diagonal insulators. These support insulators and diagonal insulators ensure that the equipment on the steel platform meets ground insulation requirements. One end of the series compensation device installed on the steel platform is connected to the steel platform, and all equipment on the steel platform has no electrical connection to the ground. During normal operation, the steel structure platform and the ground are equivalent to a flat-plate capacitor. Its stray capacitance is inversely proportional to the distance to the ground and directly proportional to the area of ​​the steel structure platform. The length, width and height of the UHV series-compensated steel structure platform are 27m×12m×10.5m, and its stray capacitance to the ground is about 1400pF. When the UHV series-compensated steel structure platform is charged, a large transient overcurrent flows through the adjacent capacitive voltage transformer, causing damage.

[0004] Typical 1000kV UHV large capacity fixed series compensation single line diagram is as follows Figure 2As shown, its capacitor compensation capacity reaches up to 3000 Mvar / three-phase (two segments, 1500 Mvar / segment / three-phase). The two-segment series compensation utilizes isolation switches 1081 and 1082, as well as a bypass isolation switch 107, in conjunction with bypass switches 104 and 204 for activation and deactivation. The single-segment series compensation capacitor 101 (corresponding to the other segment 201) utilizes a double H-bridge arrangement. A metal oxide voltage limiter (MOV) 102 (corresponding to the other segment 202) is connected in parallel across the capacitor. A spark gap 103 (corresponding to the other segment 203) is connected in series with a damping device (consisting of a linear resistor 1052 and a nonlinear resistor 1052 connected in series with a damping reactor 1051 in parallel) and then connected in parallel across the capacitor. The bypass switch 104 is connected in parallel with the spark gap 103. In addition, current transformers 1091, 1092, 1093, 1094, 1095, 1096, 1097, 1098, and 1099 are configured to implement corresponding protection functions. The capacitor bank, metal oxide voltage limiter, damping device, and spark gap are all installed on the high-voltage insulated steel structure platform and isolated from the platform by insulators. One end of these devices is directly connected to the steel structure platform 106 (corresponding to the other section, 206) via a single pipe mother or aluminum busbar. When charging the steel structure platform for the first time, grounding switches 10811 and 10822 are opened, isolation switch 107 is closed, bypass switches 104 and 204 are closed, and isolation switch 1081 or 1082 is closed and opened to complete the charging and discharging of the steel structure platform.

[0005] The drawback of the existing technical solution is that due to the large stray capacitance of the steel structure platforms 106 and 206 to the ground, when the isolation switch 1081 or 1082 is used to charge and discharge the series-compensated steel structure platform for the first time, the adjacent capacitive voltage transformer will be damaged due to excessive fast transient current. The public document "Fast transient test of capacitive voltage transformer using ultra-high voltage disconnector to connect fixed series-compensated platform" (High Voltage Technology, 2014, 40(12): 3972-3978) points out that when the ultra-high voltage series compensation is put into operation, the adjacent capacitive voltage transformer will be damaged during the charging and discharging operations of the series-compensated steel structure platform. Subsequently, to analyze the cause of the accident, the testing unit conducted tests directly on the UHV series compensation platform. The test results showed that when the disconnector engaged the series compensation platform, a fast transient current flowed through the adjacent CVT, accompanied by a fast transient overvoltage, with an oscillation center frequency of 0.5 MHz. The above-mentioned literature proposed the use of a current-limiting reactance or resistor in series with the high-voltage end of the CVT, but this approach would affect the measurement accuracy of the CVT. The transformer manufacturer needs to compensate for the voltage division of the damping reactance or resistor to ensure that the accuracy of the CVT meets the original design requirements. To maintain the original design parameters of the CVT and avoid damage to the CVT, the present invention proposes a series compensation device topology structure, namely, a high-frequency damping circuit is connected in series with the only connecting wire between the low-voltage busbar and the steel structure platform in the series compensation device, thereby suppressing fast transient overvoltage and overcurrent, avoiding damage to the CVT during the initial charging and discharging of the series compensation device, and also reducing fast transient overcurrent and overvoltage on the electronic equipment on the steel structure platform. Summary of the Invention

[0006] An embodiment of the present application provides a series compensation device, including a steel structure platform, a series compensation main equipment unit and a high-frequency damping circuit, wherein the two ends of the series compensation main equipment unit are respectively connected to the high-voltage busbar and the low-voltage busbar of the series compensation device, and the series compensation main equipment unit, the high-voltage busbar and the low-voltage busbar are supported by at least two insulators fixed on the steel structure platform; the high-frequency damping circuit is connected between the low-voltage busbar and the steel structure platform, and the low-voltage busbar and the steel structure platform are connected at only one point through the high-frequency damping circuit.

[0007] According to some embodiments, the series compensation main equipment unit includes a series compensation module and a protection module. The series compensation module is used to change the equivalent impedance of the access line or insert a compensation voltage in series into the access line to adjust the active and reactive power of the system; the protection module is used to protect the series compensation module.

[0008] According to some embodiments, the series compensation module includes at least one of a fixed series compensation capacitor, a thyristor controlled series compensation capacitor, a thyristor protected series capacitor, and a series resonant fault current limiter composed of a series capacitor and a reactor.

[0009] According to some embodiments, the high-frequency damping circuit includes at least one of a linear resistor, a damping inductor, a linear resistor and a damping inductor connected in parallel, a linear resistor and a nonlinear resistor connected in series and connected in parallel with a damping inductor, a linear resistor and a micro-gap connected in series and connected in parallel with a damping inductor, a ferrite, an amorphous magnetic ring, and a high-frequency filter.

[0010] According to some embodiments, the series compensation device also includes a rapid closing device and a damping device, one end of the rapid closing device is connected to the low-voltage bus; one end of the damping device is connected to the high-voltage bus, and the other end of the damping device is connected to the other end of the rapid closing device, and the damping device is supported by at least two insulators fixed on the steel structure platform.

[0011] According to some embodiments, the damping device includes a linear resistor, a nonlinear resistor, and a damping inductor, wherein the nonlinear resistor is connected in series with the linear resistor; and the damping inductor is connected in parallel with the linear resistor and the nonlinear resistor connected in series.

[0012] According to some embodiments, the fast closing device includes at least one of a spark gap and a bypass switch connected in parallel, a plasma gap and a bypass switch connected in parallel, a closed gap and a fast vacuum switch and a bypass switch connected in parallel, a power electronic switch and a bypass switch connected in parallel, a spark gap and a fast vacuum switch connected in parallel, a plasma gap and a fast vacuum switch connected in parallel, and a closed gap and a fast vacuum switch connected in parallel.

[0013] According to some embodiments, the spark gap, plasma gap, sealed gap, fast vacuum switch, and power electronic switch are supported by at least two insulators fixed on the steel structure platform.

[0014] According to some embodiments, the connection point between the low-voltage busbar and the steel structure platform, which is connected only by the high-frequency damping loop, is the midpoint of the total length of the low-voltage busbar on the steel structure platform.

[0015] According to some embodiments, the series compensation device further includes a current transformer, and the current transformer is used to implement overcurrent protection.

[0016] The technical solution provided in the embodiment of the present application is that the entire steel structure platform is connected to other equipment at only one point through a high-frequency damping circuit, which effectively reduces the rapid transient overvoltage and transient overcurrent generated when the steel structure platform of the series compensation device is charged and discharged using an isolation knife switch; the electromagnetic interference on the control cables and electronic equipment on the platform will also be suppressed and reduced to a certain extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0018] Figure 1 It is a structural diagram of a series flexible AC transmission device connected to a power system.

[0019] Figure 2 It is a typical UHV segmented large-capacity fixed series compensation single line diagram.

[0020] Figure 3 This is a topological diagram of a series compensation device provided in this application.

[0021] Figure 4a-4f It is a schematic diagram of the composition of the high-frequency damping circuit provided by this application.

[0022] Figure 5 This is a schematic diagram of a series compensation device provided by this application. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without making creative efforts are within the scope of protection of this application.

[0024] It should be understood that the terms "include" and "comprising" used in the description and claims of this application indicate the presence of described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0025] Figure 3 This is a topological diagram of a series compensation device provided in this application. The series compensation device includes a steel structure platform 309, a series compensation main equipment unit 301 and a high-frequency damping circuit 308.

[0026] The steel structure platform 309 supports the series compensation main unit 301 and the high-frequency damping circuit 308. The two ends of the series compensation main unit 301 are connected to the high-voltage busbar 307 and low-voltage busbar 306 of the series compensation device, respectively. The series compensation main unit 301, high-voltage busbar 307, and low-voltage busbar 306 are supported by at least two insulators fixed to the steel structure platform 309.

[0027] The high-frequency damping loop 308 is connected between the low-voltage busbar 306 and the steel structure platform 309 , and the low-voltage busbar 306 and the steel structure platform 309 are connected at only one point via the high-frequency damping loop 308 .

[0028] According to some embodiments, the series compensation device further includes a rapid closing device 302 and a damping device 303. One end of the rapid closing device 302 is connected to a low-voltage busbar 306. One end of the damping device 303 is connected to a high-voltage busbar 307, and the other end is connected to the other end of the rapid closing device 302. The damping device 303 is supported by at least two insulators fixed to a steel structure platform 309. The rapid closing device 302 and the damping device 303 are connected in series and then connected in parallel to the series compensation main device unit 301.

[0029] The series compensation main equipment unit 301 includes a series compensation module and a protection module. The series compensation module is used to perform reactive power compensation on the connected line. The protection module is used to protect the series compensation module.

[0030] The series compensation module includes but is not limited to at least one of a fixed series compensation capacitor, a thyristor controlled series compensation capacitor, a thyristor protected series capacitor, and a series resonant fault current limiter composed of a series capacitor and a reactor.

[0031] The high-frequency damping circuit 308 includes but is not limited to at least one of a linear resistor, a damping inductor, a linear resistor and a damping inductor connected in parallel, a linear resistor and a nonlinear resistor connected in series and then connected in parallel with a damping inductor, a linear resistor and a micro-gap connected in series and then connected in parallel with a damping inductor, ferrite, an amorphous magnetic ring, and a high-frequency filter.

[0032] A preferred embodiment of the damping device 303 is a type in which a nonlinear resistor and a linear resistor are connected in series and then connected in parallel with a damping inductor, but the present invention is not limited thereto.

[0033] When the series compensation main equipment unit 301 has a relatively high closing time requirement for the fast closing device 302 (e.g., a closing time ≤ 1ms), the fast closing device 302 can be combined. The fast closing device 302 includes, but is not limited to, at least one of a spark gap and a bypass switch connected in parallel, a plasma gap and a bypass switch connected in parallel, a sealed gap and a fast vacuum switch and a bypass switch connected in parallel, a power electronic switch and a bypass switch connected in parallel, a spark gap and a fast vacuum switch connected in parallel, a plasma gap and a fast vacuum switch connected in parallel, or a sealed gap and a fast vacuum switch connected in parallel. The spark gap, plasma gap, sealed gap, fast vacuum switch, and power electronic switch are supported by at least two insulators fixed to the steel structure platform 309.

[0034] The rapid closing device 302 is connected to the low-voltage bus 306 via an isolating switch 3051 with a single or dual earthing switch. The rapid closing device 302 is connected to the high-voltage bus 307 via an isolating switch 3052 with a single or dual earthing switch. A bypass isolating switch 304 is connected in series with the transmission line and is connected to the other ends of the isolating switches 3051 and 3052. The coordination between the isolating switches 3051, 3052, the bypass isolating switch 304, and the rapid closing device 302 enables the series compensation device to be activated and deactivated.

[0035] The low-voltage busbar 306 and the steel structure platform 309 are connected only through the high-frequency damping loop 308 , and the preferred connection point is the midpoint of the total length of the low-voltage busbar 306 on the steel structure platform 309 .

[0036] During normal operation, close the fast closing device 302, close the bypass isolation knife gate 304, open the isolation knife gate 30511 and the isolation knife gate 30522, and then close the isolation knife gate 3051 (or 3052). At this time, because the capacitance of the adjacent capacitor voltage transformer is charged by the isolation knife gate 3051 (or 3052) and the ground stray capacitance of the steel structure platform 309, a fast transient overvoltage and overcurrent will be generated in the loop. Then the bypass isolation knife gate 304 is opened, and finally the fast closing device 302 is opened, and the series compensation device is put into operation. At this time, the current in the transmission line only flows through the series compensation main equipment unit 301, and no current flows in the high-frequency damping circuit 308.

[0037] The high frequency damping circuit 308 is composed as follows: Figure 4a-4f shown. Figure 4a It is a damping inductor method. Figure 4b It is a damping resistor method. Figure 4c The damping inductor 403 and the damping resistor 404 are connected in parallel. Figure 4d The nonlinear resistor 407 is connected in series with the linear resistor 406 and then connected in parallel with the damping inductor 405 . Figure 4e The micro spark gap 409 is connected in series with the linear resistor 410 , and then connected in series with the damping inductor 408 . Figure 4f It is a ferrite or amorphous magnetic ring 411.

[0038] In addition to the above-mentioned high-frequency damping circuit types, other high-frequency damping devices such as high-frequency electromagnetic interference filters can also be selected. Various high-frequency damping circuit methods can be specifically simulated and studied based on the size of the actual series compensation device's stray capacitance to ground and the discharge circuit, and the appropriate method can be selected based on the cost of various high-frequency damping circuits. The preferred solution is Figure 4d The nonlinear resistor 407 is connected in series with the linear resistor 406 and then connected in parallel with the damping inductor 405. Figure 4f Ferrite ring 411 type.

[0039] The technical solution provided in this embodiment is that the entire steel structure platform is connected to other equipment at only one point through a high-frequency damping circuit, which effectively reduces the rapid transient overvoltage and transient overcurrent generated when the steel structure platform of the series compensation device is charged and discharged using an isolation knife switch; the electromagnetic interference on the control cables and electronic equipment on the platform will also be suppressed and reduced to a certain extent.

[0040] Figure 5 This is a schematic diagram of a series compensation device provided by this application.

[0041] The series compensation device includes a steel structure platform 506 , a series compensation main equipment unit and a high-frequency damping loop 510 .

[0042] The steel structure platform 506 supports the main series compensation unit and high-frequency damping circuit 510. The two ends of the main series compensation unit are connected to the high-voltage busbar 512 and low-voltage busbar 511 of the series compensation device, respectively. The main series compensation unit, high-voltage busbar 512, and low-voltage busbar 511 are supported by at least two insulators fixed to the steel structure platform 309.

[0043] The high-frequency damping loop 510 is connected between the low-voltage busbar 511 and the steel structure platform 506 , and the low-voltage busbar 511 and the steel structure platform 506 are connected at only one point via the high-frequency damping loop 510 .

[0044] The series compensation main equipment unit includes a series compensation module and a protection module. The series compensation module is used to compensate for the equivalent impedance of the access line. The protection module is used to protect the series compensation module.

[0045] The series compensation module includes a capacitor bank 501. The protection module includes a metal oxide voltage limiter 502. The capacitor bank 501 adopts a double H-bridge arrangement, and the metal oxide voltage limiter 502 is connected in parallel with the capacitor bank 501.

[0046] According to some embodiments, the series compensation device also includes a rapid closing device and a damping device. One end of the rapid closing device is connected to the low-voltage busbar 511. One end of the damping device is connected to the high-voltage busbar 512, and the other end of the damping device is connected to the other end of the rapid closing device. The damping device is supported by at least two insulators fixed to the steel structure platform 506. The rapid closing device and the damping device are connected in series and then connected in parallel to the series compensation main unit.

[0047] The rapid closing device includes a spark gap 503 and a bypass switch 504 connected in parallel. Spark gap 503 is connected in series with a damping device and then in parallel with capacitor bank 501. Bypass switch 504 is connected in parallel with spark gap 503. Busbar 511 on the platform connected to isolating switch 5081 is defined as a low-voltage busbar, and busbar 512 on the platform connected to isolating switch 50822 is defined as a high-voltage busbar. Low-voltage busbar 511 and high-voltage busbar 512 are supported by at least two insulators fixed to a steel structure platform 506. The two ends of capacitor bank 501 are connected to low-voltage busbar 511 and high-voltage busbar 512, respectively. Bypass isolating switch 507 is connected in series with the transmission line and connected to the other ends of isolating switches 5081 and 5082.

[0048] The damping device includes a nonlinear resistor 5052 , a linear resistor 5053 and a damping reactor. The nonlinear resistor 5052 and the linear resistor 5053 are connected in series and then connected in parallel with the damping reactor 5051 .

[0049] The series compensation device also includes isolation switches 5081 and 5082 , corresponding ground switches 50811 and 50822 , and a bypass isolation switch 507 .

[0050] Current transformers 5093 and 5094 are installed in the middle branch of the capacitor double H-bridge. Current transformers 5095 and 5096 are installed on the conductor connecting the metal oxide voltage limiter 502 to the low-voltage busbar 511. Current transformer 5097 is installed on the conductor connecting the spark gap 503 to the low-voltage busbar 511. Current transformer 5098 is installed on the conductor connecting the bypass switch to the low-voltage busbar 511. Current transformer 5091 is arranged on the incoming side of the transmission line. A high-frequency damping circuit 510 is connected in series between the low-voltage busbar 511 and the steel structure platform 506, and current transformer 5099 is installed on the connecting conductor. Current transformers are used to implement overcurrent protection.

[0051] Capacitor bank 501, metal oxide voltage limiter 502, spark gap 503, damping equipment, and all current transformers are mounted on a steel structure platform 506 and supported by support insulators (or alternatively, air gap insulation or other insulating media) to achieve electrical isolation from the steel structure platform. The entire steel structure platform 506 is connected to other equipment only through a high-frequency damping circuit 510. The preferred installation location for the steel structure platform 506 and high-frequency damping circuit 510 is midway along the total length of the low-voltage busbar 511 on the steel structure platform 506.

[0052] The technical solution provided in this embodiment is that the entire steel structure platform is connected to other equipment at only one point through a high-frequency damping loop. The preferred installation location of the connection is the midpoint of the total length of the low-voltage busbar on the steel structure platform. This further effectively reduces the rapid transient overvoltage and transient overcurrent generated when the steel structure platform of the series compensation device is charged and discharged using an isolation knife switch; the electromagnetic interference on the control cables and electronic equipment on the platform will also be suppressed and reduced to a certain extent.

[0053] The above embodiments are only for illustrating the technical ideas of the present application and cannot be used to limit the scope of protection of the present application. Any changes made on the basis of the technical solutions in accordance with the technical ideas proposed in the present application shall fall within the scope of protection of the present application.

Claims

1. A series compensation device comprising: Steel structure platform; A series compensation main equipment unit, with two ends respectively connected to the high-voltage busbar and the low-voltage busbar of the series compensation device, and the series compensation main equipment unit, the high-voltage busbar and the low-voltage busbar are supported by at least two insulators fixed on the steel structure platform; A high-frequency damping circuit is connected between the low-voltage busbar and the steel structure platform, and the low-voltage busbar and the steel structure platform are connected at only one point through the high-frequency damping circuit; The series compensation main equipment unit includes: Series compensation module, used to change the equivalent impedance of the access line or insert a compensation voltage in series into the access line to adjust the active power and reactive power of the system; Protection module, used to protect the series compensation module; The high-frequency damping circuit includes at least one of a linear resistor, a damping inductor, a linear resistor and a damping inductor connected in parallel, a linear resistor and a nonlinear resistor connected in series and connected in parallel with a damping inductor, a linear resistor and a micro-gap connected in series and connected in parallel with a damping inductor, a ferrite, an amorphous magnetic ring, and a high-frequency filter.

2. The series compensation device according to claim 1, wherein: The series compensation module includes at least one of a fixed series compensation capacitor, a thyristor controlled series compensation capacitor, a thyristor protected series capacitor, and a series resonant fault current limiter composed of a series capacitor and a reactor.

3. The series compensation device according to claim 1, further comprising: A fast closing device, one end of which is connected to the low-voltage busbar; A damping device has one end connected to the high-voltage busbar and the other end connected to the other end of the rapid closing device. The damping device is supported by at least two insulators fixed on the steel structure platform.

4. The series compensation device according to claim 3, wherein: The damping device comprises: Linear resistor, a nonlinear resistor connected in series with the linear resistor; A damping inductor is connected in parallel with the series-connected linear resistor and nonlinear resistor.

5. The series compensation device according to claim 3, wherein: The fast closing device includes at least one of a spark gap and a bypass switch connected in parallel, a plasma gap and a bypass switch connected in parallel, a sealed gap and a fast vacuum switch and a bypass switch connected in parallel, a power electronic switch and a bypass switch connected in parallel, a spark gap and a fast vacuum switch connected in parallel, a plasma gap and a fast vacuum switch connected in parallel, and a sealed gap and a fast vacuum switch connected in parallel.

6. The series compensation device according to claim 5, wherein: The spark gap, plasma gap, sealed gap, fast vacuum switch and power electronic switch are supported by at least two insulators fixed on the steel structure platform.

7. The series compensation device according to claim 1, wherein: The connection point between the low-voltage busbar and the steel structure platform, which is connected only by the high-frequency damping loop, is the midpoint of the total length of the low-voltage busbar on the steel structure platform.

8. The series compensation device according to claim 1, further comprising: Current transformer, used for overcurrent protection.

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