WO2014201809A1 - 一种不停电直流融冰装置 - Google Patents

一种不停电直流融冰装置 Download PDF

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Publication number
WO2014201809A1
WO2014201809A1 PCT/CN2013/088474 CN2013088474W WO2014201809A1 WO 2014201809 A1 WO2014201809 A1 WO 2014201809A1 CN 2013088474 W CN2013088474 W CN 2013088474W WO 2014201809 A1 WO2014201809 A1 WO 2014201809A1
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WO
WIPO (PCT)
Prior art keywords
circuit
ice
switch
phase
melting
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PCT/CN2013/088474
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English (en)
French (fr)
Inventor
荆平
周飞
宋洁莹
邱宇峰
苏雪源
詹建荣
陈颖
Original Assignee
国家电网公司
国网智能电网研究院
国网福建省电力有限公司
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Application filed by 国家电网公司, 国网智能电网研究院, 国网福建省电力有限公司 filed Critical 国家电网公司
Publication of WO2014201809A1 publication Critical patent/WO2014201809A1/zh

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02G—INSTALLATION OF ELECTRIC CABLES OR LINES, OR OF COMBINED OPTICAL AND ELECTRIC CABLES OR LINES
    • H02G1/00—Methods or apparatus specially adapted for installing, maintaining, repairing or dismantling electric cables or lines
    • H02G1/02—Methods or apparatus specially adapted for installing, maintaining, repairing or dismantling electric cables or lines for overhead lines or cables
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02G—INSTALLATION OF ELECTRIC CABLES OR LINES, OR OF COMBINED OPTICAL AND ELECTRIC CABLES OR LINES
    • H02G7/00—Overhead installations of electric lines or cables
    • H02G7/16—Devices for removing snow or ice from lines or cables
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/02—Circuit arrangements for ac mains or ac distribution networks using a single network for simultaneous distribution of power at different frequencies; using a single network for simultaneous distribution of ac power and of dc power

Definitions

  • the invention belongs to the technical field of power electronics, and particularly relates to an uninterrupted DC ice melting device. Background technique
  • the problem of ice icing on power lines is often caused in winter, causing serious disasters to the power grid.
  • the methods for solving the problem of icing are divided into mechanical deicing or thermal melting ice, wherein the thermal melting ice is divided into two types: power-off melting and non-stopping ice melting.
  • Hot ice melting has been applied in the power grid, and the implementation methods include AC short circuit upflow melting ice and DC current melting ice.
  • the former connects 2 ⁇ 3 ice-melting lines through the knife gate, one end is manually short-circuited, and the other end is connected to the AC power source for short-circuit melting.
  • the advantage is that no special equipment is needed and the production site is practical.
  • the disadvantage is that the number of series lines needs to be calculated and selected. When the power supply is switched, the impact on the power grid is large.
  • the short-circuit up-flow process consumes a lot of reactive power and has a great influence on the grid voltage. It is not suitable for 500kV and above lines.
  • Another method of power-off and ice-melting is to use SVC as the ice-melting device.
  • SVC SVC type reactive static compensation device
  • the SVC type reactive static compensation device is added to the two phases of the first stage.
  • the output DC voltage is DC short-circuited to the two phases of the line, and then the third phase is melted.
  • the advantage is that the DC voltage output from the device is adjustable and can be adapted to any length and voltage level. Does not consume system failure.
  • As an ice melting device when icing it is usually used as a reactive static compensation device, and the equipment utilization rate is high.
  • the disadvantage is that it can only melt two phases at a time, the ice melting time is long, the knife gate operation and the manual setting of the short-circuit line have a large workload, and the power is cut off.
  • the current non-blackout thermal ice melting method is as follows: The ice melting station is constructed in the middle of the line, and the ice splitting circulation is added to each phase double splitting wire, and the thermal effect co-occurring with the load current is superimposed to realize non-stop electric melting ice.
  • an ice melting station should be built on each line, the investment is large, the equipment utilization rate is low, the object of use must be double-split conductor, the limitation is large, and the ice melting station is built in the middle of the line, which is difficult to maintain and difficult to promote and apply.
  • Embodiments include transferring the load of a plurality of lines to a line to melt the ice by scheduling the cut-off line. This method has certain feasibility for a line with a smaller cross-section of l lOkV and below, and for a line of a voltage level of 220 kV and above.
  • the line section is large, combined with system capacity and operating mode limitations, and system stability issues exist for all voltage grade lines.
  • the method of increasing the load and melting ice also includes adopting a back-to-back voltage source converter, which forms a unified power flow controller wiring form when there is a demand for melting ice, and the transformer flows into the ice melting line to widen the current of the line. Since the line reactance is much larger than the line resistance, the melting current is much larger than the line normal load current, and the melting power is basically provided by the voltage source converter. As the length of the line transmission line increases, the capacity demand for the ice melting device increases dramatically. At present, the large-capacity voltage source converter based on the full control device is very expensive, so the method is not practically feasible.
  • the power-off and ice-melting method affects the normal power supply of the line, and the manual connection of the short-circuit line and the power-off operation has a large workload and a long time; the existing ice-melting technology under the no-power-off mode is still in its present stage. Without universal promotion conditions, it is necessary to seek a new type of non-stop ice melting technology with high cost performance. Summary of the invention
  • the present invention proposes an uninterruptible DC ice melting device, which realizes the melting of the line under the state of no power failure, and the ice melting process does not affect the normal transmission of the current.
  • the invention provides an uninterruptible DC ice melting device, which is improved in that the device comprises a voltage regulating circuit, an AC-DC converting circuit, a resonant circuit I and a resonant circuit ⁇ ; one end of the voltage regulating circuit and the substation station The power supply busbar is connected, and the other end is connected to the AC-DC conversion circuit and the resonant circuit I in sequence; the resonant circuit is disposed in the segmented busbar where the non-melting ice line of the station is located and the segmented busbar where the ice melting circuit is located, which includes the serial connection. Inductance and capacitance.
  • the voltage regulating circuit is an on-load voltage regulating transformer
  • the primary side of the on-load tap-changer is connected to the power supply busbar in the station, and the secondary side thereof is connected to the AC-DC converter circuit.
  • the voltage regulating circuit comprises a transformer I, a power electronic converter and a transformer connected in sequence
  • the primary side of the transformer 1 is connected to the power supply busbar in the station, and the secondary side thereof is connected to one end of the power electronic conversion device; the other end of the power electronic conversion device is connected to the primary side of the transformer, the transformer
  • the secondary side of the ⁇ is connected to the AC-DC conversion circuit.
  • the power electronic conversion device is composed of an uncontrolled rectifier, capacitor and voltage source converter I connected in parallel; or The voltage source converter ⁇ , the capacitor and the voltage source converter m are sequentially connected in parallel.
  • the AC-DC conversion circuit includes an uncontrollable rectifier circuit or a controllable rectifier circuit; the AC terminal of the uncontrollable rectifier circuit or the controllable rectifier circuit is connected to the voltage regulation circuit, and the DC terminal and the power grid are divided.
  • the segment bus is connected to the bypass bus.
  • the resonant circuit is connected between the positive and negative terminals of the DC terminal of the AC-DC converting circuit
  • the resonant circuit 1 includes an inductor and a capacitor in series.
  • the device comprises a tap changer
  • the tap changer comprises a switch I, a switch ⁇ ; the switch I comprises a single-phase switch PA, a single-phase switch PB and a single-phase switch PC; the switch II comprises a single-phase switch NA, a single-phase switch NB and a single-phase switch NC;
  • the positive and negative poles of the DC terminal of the AC-DC converter circuit are respectively connected to the in-station segment bus and the bypass bus through the tap changer I and the tap changer ; when the positive pole is connected to the segment bus, the switch I is passed through The single-phase switch PA, the single-phase switch PB, and the single-phase switch PC are respectively connected to the three-phase of the segmented bus bar; when the negative pole is connected to the bypass bus, the single-phase switch NA in the switch ⁇
  • the single-phase switch NB and the single-phase switch NC are respectively connected to the three-phase of the bypass bus.
  • the invention realizes the melting of the line under the state of no power failure, and the ice melting process does not affect the normal transmission of the current flow.
  • the invention realizes the DC melting ice, significantly reduces the capacity of the ice melting device, and has application feasibility.
  • the melting ice current path of the invention is limited to the melting ice line, does not interfere with the important equipment in the substation, the power supply or load in the station, and the system runs safely and stably during the melting process.
  • the control method of the invention is relatively simple, high in reliability, strong in melting ice, small in interference to the system, suitable for 220kV and above power grids, and suitable for melting ice of single power lines.
  • FIG. 1 is a circuit diagram of a circuit of a non-power-off ice melting device provided by the present invention.
  • FIG. 2 is a diagram of a direct current direct current path of a phase A melting ice provided by the present invention.
  • FIG. 3 is a waveform diagram of current lines of transmission lines in various systems provided by the present invention.
  • FIG. 4 is a waveform diagram of power and load currents of various systems provided by the present invention.
  • FIG. 5 is a waveform diagram of bus voltages in various systems provided by the present invention.
  • FIG. 6 is a structural diagram of a main circuit of an ice melting device based on an on-load tap-changer according to the present invention.
  • FIG. 7 is a structural diagram of a main circuit of an ice melting device based on a power electronic voltage regulating circuit according to the present invention.
  • FIG. 8 is a schematic structural diagram of a main circuit of an ice melting device based on a power electronic voltage regulating circuit according to the present invention.
  • thermal melting ice it is the basic idea of thermal melting ice to superimpose the voltage source at both ends of the transmission line forming the loop to form a circulating current so that the current of the ice-melting line is significantly increased. Since the line resistance is much smaller than the line reactance, the efficiency of melting the ice using the DC voltage source is much higher than that of the AC voltage source without changing the line parameters. However, DC current can cause serious magnetic distortion in equipment such as power transformers, which makes the system unable to operate safely and stably. Effective measures must be taken.
  • the left side of the figure is a station
  • the right side is a station B
  • the non-stop power melting device is installed at station A.
  • the system power supply is the equivalent model of the transmission system connected to the station.
  • the power supply of the station system is connected to the I-segment bus, and the bus-coupled switches BRK1 and BRK2 are in the closed state.
  • the two busbars of station B can be combined or opened, and no requirements are required. That is, the substation without ice-melting device does not need to change the state of the busbar segmentation, and all the non-stop power-melting operations are carried out at station A.
  • the ice-melting line L2 is connected to the II-section busbar, and the ice-melting line L3 is connected to the parent side, and the system supplies power normally.
  • the three-phase AC current of the bus-coupled switch BRK1 is opened, and the three-phase AC current connected in parallel with the three-phase 50Hz series resonant branch does not affect the normal power supply.
  • a 50Hz series resonant branch is connected between the A-phase bus and the A-phase A phase, and then the A-phase of the bus-coupled switch BRK2 is opened, and the A-phase AC current passes through the 50Hz series resonant branch, which does not affect the normal power supply. .
  • An adjustable DC voltage source is connected in parallel with the 50Hz series resonant branch.
  • the DC current can be injected into the A phase of the ice melting circuit as needed.
  • the DC current flows from the A of the ice melting line L2 and the A phase of the melting ice line L3. Does not affect the normal power supply of the power supply and load.
  • the main function of the three-phase 50Hz series resonant branch is to isolate the DC from the power supply and the load, and does not affect the normal power supply of the line.
  • the branch current is equal to the sum of the normal supply currents of the ice melting lines L2 and L3.
  • the main function of the single-phase 50Hz series resonant branch is to bypass the power frequency current to prevent it from flowing into the rectifier circuit without affecting the normal power supply of the line.
  • the branch current is equal to the normal supply current of the ice melting line L3.
  • the DC current path is as shown in FIG. 2.
  • the ice melting device injects a direct current voltage into the phase A of the segment II bus and the bypass bus, and the direct current constitutes a closed loop through the phase A of the ice melting line L2 and the phase A line of the melting ice line L3. Since the LC resonant circuit isolates the DC component, the DC current does not flow to the power supply and load, which ensures normal power supply to the system.
  • the above steps are simulated and verified, and the current waveforms of the non-melting ice line L1 and the ice melting line L2, L3, and the equivalent system power supply on both sides are observed, as shown in FIG. 3, wherein the first waveform is a non-melting ice line.
  • the current waveform contains no DC component;
  • the second waveform is the waveform of the ice melting circuit 1,
  • the phase A contains the lower bias DC component;
  • the third waveform is the current waveform of the ice melting circuit 2, and the phase A contains the upward biased DC component.
  • the current waveforms of the loads of the non-melting ice line L1 and the melting ice lines L2, L3 are observed, as shown in Fig.
  • the three waveforms are the current waveforms of the power supply and the load transformer on both sides, and do not contain the DC component. It can be seen that the DC current only forms a loop between the ice melting lines L2 and L3, and the magnitude of the DC component can be adjusted online according to the line melting ice.
  • the voltage simulation waveforms of the relevant busbars and the resonant branch are shown in Figure 5.
  • the bus voltages of the I-segment of the station A and the busbars of the I and the slabs of the station B are normal and do not contain the DC component.
  • a station two-stage bus A phase voltage and bypass bus A phase voltage contains DC bias of the same size and opposite direction, which is half the DC melting voltage. Due to the small line resistance, the melting ice voltage of several thousand volts does not affect the normal operation of the substation bus.
  • the scheme can realize the melting of the A phase, the B phase and the C phase under the condition of ensuring no power failure. If three ice melting devices are installed in the station at the same time, simultaneous melting of the A phase, B phase and C phase lines can be achieved.
  • the ice melting device can adopt different main circuit structures, which will be described in detail below in conjunction with specific embodiments.
  • Example 1
  • the device comprises a voltage regulating circuit, an AC-DC converting circuit, a resonant circuit I and a resonant circuit ⁇ ; the voltage regulating circuit is an on-load voltage regulating transformer; the primary side is connected with the power supply busbar in the station, such as a 35kV bus bar in a typical 220kV substation, The secondary side is sequentially connected to the AC-DC conversion circuit and the resonance circuit 1.
  • the AC-DC conversion circuit includes an uncontrollable rectifier circuit or a controllable rectifier circuit.
  • a diode uncontrollable rectifier circuit is used, and the AC terminal is connected to the voltage regulation circuit, and the DC terminal is connected to the grid bus and the bypass bus, according to the wire parameters.
  • the melting current demand is injected into the line with a DC voltage to obtain a melting current.
  • a resonant circuit I is connected between the positive and negative terminals of the DC terminal of the AC-DC converting circuit, and two pairs of devices are arranged When the line A phase, B phase or C phase line is injected with DC current, it is used to provide a path for the AC current of the phase, and isolate the DC component, which does not affect the normal power supply of the system, and prevents the AC current of the transmission line from flowing into the AC-DC conversion.
  • the circuit realizes the purpose of not stopping electricity and melting ice. It includes inductors and capacitors in series.
  • the resonant circuit ⁇ (ie, the three-phase series resonant circuit) provided in this embodiment is disposed at the segment busbar and the ice melting circuit where the non-melting ice line is located in the station.
  • the segmented busbar prevents the DC ice-melting current from flowing into the non-melting ice line, the main transformer or the transmission system in the station, and provides a path for the three-phase AC current without affecting the normal power supply of the system.
  • the resonant circuit includes inductors and capacitors in series.
  • a tap changer is added for the ice-cooling current selection path;
  • the tap changer includes the switch I and the switch ⁇ ; the positive and negative terminals of the DC terminal of the AC-DC conversion circuit respectively pass
  • the tap changer I and the ⁇ are connected to the in-station segment bus and the bypass bus; when the positive pole is connected to the segment bus, the single-phase switches PA, PB and PC in the switch I are respectively connected to the three-phase of the segment bus
  • the single-phase switches NA, NB and NC in the switch ⁇ are connected to the three-phase of the bypass bus (ie, the A phase is connected to the PA and the NA, the B phase is connected to the PB and NB, Phase C connects PC and NC).
  • the switching is performed by the tap changer, and the DC voltage is injected in phases between the segment II bus and the bypass bus.
  • the DC voltage is superimposed on both ends of the melting ice circuit resistance, and a DC current is injected into the circuit.
  • the voltage at the regulator output can be varied depending on the melting demand to achieve the desired DC current.
  • This embodiment is basically the same as Embodiment 1, except that the main circuit structure is based on a power electronic voltage regulator circuit, as shown in FIG.
  • the rectifier transformer isolates the power bus, steps down and rectifies it through the diode, and then inverts the DC voltage to AC voltage through VSC. It is connected in series to the ice melting circuit through a step-up transformer and a diode rectifier bridge.
  • the VSC AC output voltage is flexible and fast adjustable, and the AC voltage can be changed in a wide range, and then the transformer is boosted and uncontrolled rectifier circuit AC-DC conversion is performed. Get the DC voltage required to melt the ice.
  • the input voltage of the voltage regulating circuit be Uvl
  • the first stage transformer ratio is kl
  • the first stage DC voltage is Udcl
  • the VSC modulation degree is m
  • the second stage transformer has a transformation ratio of k2
  • the output voltage is Uv2.
  • the voltage regulator circuit has the following relationship:
  • the advantage of this topology is that the DC voltage can be flexibly controlled by the modulation of the VSC to obtain a wide range of continuous DC voltage output without the need for the system to provide reactive power compensation. Applicable to the occasion of different ice melting line length or line shape in 220kV or 500kV substation.
  • This embodiment is basically the same as Embodiment 1, except that the main circuit structure is based on a power electronic voltage regulating circuit, a back-to-back connected voltage source converter is used, and a tap changer is added, as shown in FIG.
  • the rectifier transformer isolates the power bus and steps it down, then rectifies it through the voltage source converter VSC1, and then inverts the DC voltage to AC voltage through VSC2. Then, the step-up transformer and the diode rectification bridge are connected in series to the ice melting circuit.
  • the VSC AC output voltage is flexible and fast adjustable, and the AC voltage can be changed in a wide range, and then the transformer is boosted and uncontrolled rectifier circuit AC-DC conversion is performed. Get the DC voltage required to melt the ice.
  • the tap changer comprises a switch V and a switch VI; the switch V is connected between the AC terminal of the AC-DC converter circuit and the segment bus; the switch VI is connected between the AC terminal of the AC-DC converter circuit and the bypass bus.

Abstract

一种不停电的直流融冰装置，该融冰装置安装在线路一侧变电站内，在该变电站内可完成对该融冰装置的所有操作。该融冰装置包括调压电路、交直流变换电路、第一谐振电路和第二谐振电路；调压电路一端与变电站站内供电母线连接，另一端依次与交直流变换电路和第一谐振电路连接；第二谐振电路设置在变电站站内非融冰线路所在分段母线与融冰线路所在分段母线之间。该融冰装置在不影响正常供电的基础上，在融冰线路叠加直流融冰电流，并使融冰电流仅在融冰线路中循环，不干扰变电站内主变压器等重要设备。该融冰装置具有融冰效率高、装置容量小的优点。

Description

一种不停电直流融冰装置
技术领域
本发明属于电力电子技术领域， 具体涉及一种不停电直流融冰装置。 背景技术
一些地区冬季常现电力线路覆冰问题，给电网带来严重灾害。解决覆冰问题 的方法分为机械除冰或热力融冰，其中热力融冰又分为停电融冰和不停电融冰两 类。
停电热力融冰已在电网中应用，实施方式包括交流短路升流融冰和直流电流 融冰。前者将 2~3条待融冰线路通过刀闸操作串接， 一端人工短路， 另一端接入 交流电源进行短路融冰。其优点在于无需专用设备， 生产现场实用。缺点在于需 要对串联线路的条数进行计算、选定， 投切电源时对电网冲击较大， 短路升流过 程要消耗大量无功， 对电网电压影响大， 不适用于 500kV及以上线路。 另一种 停电融冰方式是利用 SVC兼作为融冰装置， 当线路发生覆冰后将线路停运， 线 路末端人工短路， 先在首段的两相上加入经 SVC型无功静补装置整流输出的直 流电压， 对线路的两相进行直流短路融冰， 结束后再对第三相融冰。其优点在于 装置输出的直流电压可调，可适应于任何长度和电压等级的线路。不消耗系统无 功。 覆冰时作为融冰设备， 平时作为无功静止补偿装置， 设备利用率高。 缺点是 一次只能融两相， 融冰时间长， 刀闸操作及人工设置短路线工作量大， 且要停电 进行。
目前使用的不停电热力融冰方法为： 在线路中部建设融冰站，给每相双分裂 导线加上融冰环流，和负荷电流共同发生的热效应叠加实现不停电融冰。但每条 线路上都要建一座融冰站，投入大，设备利用率低，使用对象必须是双分裂导线， 局限性大， 且融冰站建在线路中部， 维护困难， 难以推广应用。
不停电融冰的其他方式尚未在电网中实践，其中一种为基于电力变压器的高 压架空线自助式不停电融冰技术， 该种方式会引发变压器的偏磁问题。另外的设 计思路为加大融冰线路负荷，利用交流电流融冰。实施方式包括通过调度切除线 路， 将多条线路的负荷转移到一条线路使其融冰， 此方法对于截面较小的 l lOkV 及以下线路有一定的可行性， 对于 220kV及以上电压等级的线路而言， 由于导 线截面大，加之系统容量和运行方式的限制， 且所有电压等级线路都存在系统稳 定问题。增加负荷融冰的方式也包括采用背靠背电压源换流器，在有融冰需求时 构成统一潮流控制器接线形式，通过变压器串入融冰线路，拉大所在线路的潮流。 由于线路电抗远大于线路电阻， 融冰电流又远大于线路正常负荷电流， 融冰功率 基本全部由电压源换流器提供。随着线路输电线路长度增加，对融冰装置的容量 需求猛增。 目前， 基于全控器件的大容量电压源换流器成本很高， 因此该方法现 实可行性不高。
综上所述， 现有融冰技术中， 停电融冰方式影响线路正常供电， 且人工挂接 短路线及停电操作工作量大， 时间长； 现有不停电方式下的融冰技术现阶段尚不 具有普遍推广条件， 需要寻求性价比较高的新型不停电融冰技术。 发明内容
针对现有技术的不足，本发明提出一种不停电直流融冰装置， 实现了不停电 状态下的线路融冰， 融冰过程不影响潮流正常传输。
本发明提供的一种不停电直流融冰装置，其改进之处在于，所述装置包括调 压电路、交-直流变换电路、谐振电路 I和谐振电路 Π; 所述调压电路一端与变电 站站内供电母线连接， 另一端依次与所述交 -直流变换电路和谐振电路 I连接； 所述谐振电路 Π设置在站内非融冰线路所在分段母线与融冰线路所在分段 母线， 其包括串联的电感和电容。
其中， 所述调压电路为有载调压变压器；
所述有载调压变压器的原边与所述站内供电母线连接， 其副边与所述交-直 流变换电路连接。
其中， 所述调压电路包括依次连接的变压器 I、 电力电子变换装置和变压器
II；
所述变压器 I的原边与所述站内供电母线连接，其副边与所述电力电子变换 装置的一端连接； 所述电力电子变换装置的另一端与所述变压器 Π原边连接， 所述变压器 Π的副边与所述交-直流变换电路连接。
其中， 所述电力电子变换装置为- 由依次并联的不可控整流、 电容和电压源换流器 I构成； 或 由依次并联的电压源换流器 π、 电容和电压源换流器 m构成。
其中， 所述交-直流变换电路包括不可控整流电路或可控整流电路； 所述不可控整流电路或可控整流电路的交流端与所述调压电路连接，其直流 端与所述电网分段母线和旁路母线连接。
其中， 在所述交-直流变换电路的直流端的正负极之间连接有所述谐振电路
I；
所述谐振电路 I包括串联的电感和电容。
其中， 所述装置包括分接开关；
所述分接开关包括开关 I、 开关 Π; 开关 I包括单相开关 PA、 单相开关 PB 和单相开关 PC; 开关 II包括单相开关 NA、 单相开关 NB和单相开关 NC; 所述交-直流变换电路的直流端的正负极分别通过分接开关 I与分接开关 Π 与站内分段母线和旁路母线连接； 其正极与所述分段母线连接时，通过所述开关 I中的单相开关 PA、 单相开关 PB和单相开关 PC分别与所述分段母线的三相相 连； 其负极与所述旁路母线连接时， 通过所述开关 Π中的单相开关 NA、 单相开 关 NB和单相开关 NC分别与所述旁路母线的三相对应相连。
与现有技术比， 本发明的有益效果为：
本发明实现了不停电状态下的线路融冰， 融冰过程不影响潮流正常传输。 本发明实现了直流融冰， 显著降低融冰装置容量， 具备应用可行性。
本发明融冰电流通路仅限于融冰线路， 不对变电站内重要设备、站内电源或 负荷造成干扰， 融冰过程中系统安全稳定运行。
本发明的控制方法相对简单， 可靠性高， 融冰针对性强， 对系统的干扰小， 适用于 220kV及以上电网， 并且适用于单电源线路的融冰。 附图说明
图 1为本发明提供的不停电融冰装置电路接线图。
图 2为本发明提供的 A相融冰直流电流通路图。
图 3为本发明提供的系统各处输电线路电流波形图。
图 4为本发明提供的系统各处电源及负荷电流波形图。
图 5为本发明提供的系统各处母线电压波形图。 图 6为本发明提供的基于有载调压变压器的融冰装置主电路结构图。
图 7为本发明提供的基于电力电子调压电路的融冰装置主电路结构图 1。 图 8为本发明提供的基于电力电子调压电路的融冰装置主电路结构图 2。 具体实施方式
下面结合附图对本发明的具体实施方式作进一步的详细说明。
在形成环路的输电线路两端叠加电压源，形成环流电流使待融冰线路电流显 著增大是热力融冰的基本思路。 由于线路电阻远小于线路电抗，在不改变线路参 数的前提下，采用直流电压源融冰的效率远高于交流电压源融冰。但直流电流会 导致电力变压器等设备出现严重的偏磁现象，使系统无法安全稳定运行， 必须采 取有效措施。
如附图 1所示，图中左侧为甲站，右侧为乙站，不停电融冰装置安装在甲站。 系统电源为甲站所接输电系统的等值模型， 甲站系统电源接 I段母线， 母联开关 BRK1和 BRK2处于合闸状态。 乙站的两段母线可以合环， 也可以开环， 不作要 求， 即未装设融冰装置的变电站不需要改变母线分段状态，所有的不停电融冰操 作都在甲站进行。
首先， 通过倒闸， 将融冰线路 L2接 II段母线， 融冰线路 L3接旁母， 系统 正常供电。然后将母联开关 BRK1三相分闸，与其并联的三相交流电流通过三相 50Hz串联谐振支路，不影响正常供电。之后在 II段母线 A相和旁母 A相之间跨 接一个 50Hz串联谐振支路， 再将母联开关 BRK2的 A相分闸， A相交流电流通 过 50Hz串联谐振支路， 不影响正常供电。
50Hz串联谐振支路两端并联一个可调直流电压源， 可以根据需要向融冰线 路的 A相注入直流电流， 直流电流从融冰线路 L2的 A相进， 从融冰线路 L3的 A相出， 不影响电源和负载的正常供电。
三相 50Hz串联谐振支路的主要作用是隔离直流， 避免其流入电源和负载， 同时不影响线路正常供电。 支路电流等于融冰线路 L2和 L3的正常供电电流之 和。
单相 50Hz串联谐振支路的主要作用是旁路工频电流，避免其流入整流电路， 同时不会影响线路正常供电。 支路电流等于融冰线路 L3的正常供电电流。 以 A相融冰为例， 直流电流通路如附图 2所示。 融冰装置向 II段母线和旁 路母线的 A相注入直流电压， 直流电流通过融冰线路 L2的 A相和融冰线路 L3 的 A相线路构成闭合回路。 由于 LC谐振电路隔离了直流分量，直流电流不会流 向电源和负荷， 可以保证系统正常供电。
对上述步骤进行仿真验证， 观测到非融冰线路 L1和融冰线路 L2、 L3， 以 及两侧等值系统电源的电流波形， 如附图 3所示，其中第一个波形为非融冰线路 电流波形， 不含直流分量； 第二个波形为融冰线路 1的波形， A相含有下偏直流 分量； 第三个波形为融冰线路 2的电流波形， A相含有向上偏的直流分量。观测 到非融冰线路 L1和融冰线路 L2、 L3的负荷的电流波形， 如附图 4所示， 这三 个波形分别为两侧电源和负载变压器电流波形， 不含直流分量。可以看出， 直流 电流仅在融冰线路 L2和 L3之间构成回路， 直流分量的大小可根据线路融冰需 要在线调节。
相关母线和谐振支路的电压仿真波形如附图 5所示， 甲站 I段母线和乙站 I 段和 Π段母线电压都正常， 不含直流分量。 甲站二段母线 A相电压和旁路母线 A相电压含有大小相同、 方向相反的直流偏置， 大小为直流融冰电压的一半。 由 于线路电阻较小， 因此几千伏的融冰直流电压不会影响变电站母线正常操作。
通过倒闸操作， 本方案可以在保证不停电的条件下， 分别实现 A相、 B相 和 C相的融冰。如果同时在站内装设三台融冰装置， 则可实现对 A相、 B相和 C 相线路的同时融冰。
融冰装置可采用不同的主电路结构， 下面结合具体实施例进行详细说明。 实施例 1
基于有载调压变压器的不停电直流融冰装置，如附图 6所示。该装置包括调 压电路、交-直流变换电路、谐振电路 I和谐振电路 Π; 该调压电路为有载调压变 压器； 其原边与站内供电母线连接， 如典型 220kV变电站内的 35kV母线， 其副 边依次与交 -直流变换电路和谐振电路 I连接。
交 -直流变换电路包括不可控整流电路或可控整流电路， 本实施例采用二极 管不可控整流电路，其交流端与调压电路连接，其直流端与电网母线和旁路母线 连接， 依据导线参数和融冰电流需求向线路注入直流电压， 获得融冰电流。
在交 -直流变换电路的直流端的正负极之间连接有谐振电路 I，在装置对两条 线路的 A相、 B相或 C相线路注入直流电流时， 用来为该相的交流电流提供通 路， 并隔离直流分量， 不影响系统正常供电， 并防止输电线路的交流电流流入交 -直流变换电路， 实现不停电融冰的目的。 其包括串联的电感和电容。
为了隔离直流， 避免其流入电源和负载， 同时不影响线路正常供电， 本实施 例设置的谐振电路 Π (即三相串联谐振电路）设置在站内非融冰线路所在分段母 线与融冰线路所在分段母线， 防止直流融冰电流流入非融冰线路、站内主变或输 电系统， 同时为三相交流电流提供通路， 不影响系统正常供电。 谐振电路 Π包 括串联的电感和电容。
本实施例在上述的基础上， 为了方便控制， 为了融冰电流选择通路， 还添 加了分接开关； 分接开关包括开关 I、 开关 Π; 交-直流变换电路的直流端的正负 极分别通过分接开关 I和 Π与站内分段母线和旁路母线连接；其正极与所述分段 母线连接时， 通过开关 I中的单相开关 PA、 PB和 PC分别与分段母线的三相相 连； 其负极与所述旁路母线连接时， 通过开关 Π中的单相开关 NA、 NB和 NC 与旁路母线的三相对应相连（即 A相连接 PA和 NA、 B相连接 PB和 NB、 C相 连接 PC和 NC)。通过分接开关投切，轮流在 II段母线和旁路母线间分相注入直 流电压。该直流电压叠加在融冰线路电阻两端， 向回路注入直流电流。可依据融 冰需求改变调压器输出的电压， 获得所期望的直流电流。这种主电路结构的优点 是成本较低， 适用于 220kV或 500kV变电站不同融冰线路长度差别并非极其显 著的场合 。
实施例 2
本实施例基本与实施例 1相同，但区别在于该种主电路结构基于电力电子调 压电路， 如附图 7所示。 整流变压器将供电母线隔离、 降压后通过二极管整流， 之后经过 VSC将直流电压逆变为交流电压。 再通过升压变压器和二极管整流桥 串联接入融冰线路中。通过二极管不控整流和 VSC有源逆变， 利用 VSC交流输 出电压灵活、快速可调的特点， 获取能够较大范围变化的交流电压， 进而通过变 压器升压、 不控整流电路交 -直流变换， 获取融冰所需的直流电压。
设调压电路的输入电压为 Uvl， 第一级变压器变比为 kl， 第一级直流电压 为 Udcl， VSC的调制度为 m， 第二级变压器的变比为 k2， 输出电压为 Uv2， 则 调压电路有如下关系成立：
Figure imgf000009_0001
直流融冰电压: u
Figure imgf000009_0002
(2)
π 2π k k
这种拓扑结构的优点在于直流电压可以通过 VSC的调制度灵活控制， 获得 大范围的连续直流电压输出，不需要系统提供无功补偿。适用于 220kV或 500kV 变电站不同融冰线路长度或线形差别的场合。
实施例 3
本实施例基本与实施例 1相同，但区别在于，该种主电路结构基于电力电子 调压电路，采用背靠背连接的电压源换流器，并增设了分接开关，如附图 8所示。 有融冰需求时， 整流变压器将供电母线隔离、 降压后通过电压源换流器 VSC1整 流， 之后经过 VSC2将直流电压逆变为交流电压。再通过升压变压器和二极管整 流桥串联接入融冰线路中。通过二极管不控整流和 VSC有源逆变， 利用 VSC交 流输出电压灵活、快速可调的特点， 获取能够较大范围变化的交流电压， 进而通 过变压器升压、 不控整流电路交 -直流变换， 获取融冰所需的直流电压。
分接开关包括开关 V和开关 VI； 开关 V连接在交-直流变换电路的交流端 和分段母线之间； 开关 VI连接在交-直流变换电路的交流端和旁路母线之间。无 融冰需求时， 通过断开所有分接开关， 闭合开关 BRKU1、 BRKU2, 将逆变变压 器串联接入到 Π段母线和旁路母线中， 此时融冰装置调压电路中的背靠背电压 源换流器构成 UPFC结构， 可以发挥无功补偿、潮流调节等作用。使装置功能更 加强大。
最后应当说明的是： 以上实施例仅用以说明本发明的技术方案而非对其限 制，尽管参照上述实施例对本发明进行了详细的说明，所属领域的普通技术人员 应当理解： 依然可以对本发明的具体实施方式进行修改或者等同替换， 而未脱离 本发明精神和范围的任何修改或者等同替换，其均应涵盖在本发明的权利要求范 围当中。

Claims

权 利 要 求
1、 一种不停电直流融冰装置， 其特征在于， 所述装置包括调压电路、 交 - 直流变换电路、 谐振电路 I和谐振电路 Π; 所述调压电路一端与变电站站内供 电母线连接， 另一端依次与所述交 - 直流变换电路和谐振电路 I连接；
所述谐振电路 Π设置在站内非融冰线路所在分段母线与融冰线路所在分段 母线。
2、 如权利要求 1所述的不停电直流融冰装置， 其特征在于， 所述调压电路 为有载调压变压器；
所述有载调压变压器的原边与所述站内供电母线连接， 其副边与所述交-直 流变换电路连接。
3、 如权利要求 1所述的不停电直流融冰装置， 其特征在于， 所述调压电路 包括依次连接的变压器 I、 电力电子变换装置和变压器 Π;
所述变压器 I的原边与所述站内供电母线连接，其副边与所述电力电子变换 装置的一端连接； 所述电力电子变换装置的另一端与所述变压器 Π原边连接， 所述变压器 Π的副边与所述交-直流变换电路连接。
4、 如权利要求 3所述的不停电直流融冰装置， 其特征在于， 所述电力电子 变换装置为：
由依次并联的不可控整流、 电容和电压源换流器 I构成； 或
由依次并联的电压源换流器 II、 电容和电压源换流器 III构成。
5、 如权利要求 2 - 4任一所述的不停电直流融冰装置， 其特征在于， 所述交 -直流变换电路包括不可控整流电路或可控整流电路；
所述不可控整流电路或可控整流电路的交流端与所述调压电路连接，其直流 端与所述电网分段母线和旁路母线连接。
6、 如权利要求 5所述的不停电直流融冰装置， 其特征在于， 在所述交 -直流 变换电路的直流端的正负极之间连接有所述谐振电路 I；
所述谐振电路 I包括串联的电感和电容。
7、 如权利要求 1所述的不停电直流融冰装置， 其特征在于， 所述装置包括 分接开关；
所述分接开关包括开关 I、 开关 Π; 开关 I包括单相开关 PA、 单相开关 PB 和单相开关 PC; 开关 II包括单相开关 NA、 单相开关 NB和单相开关 NC; 所述交-直流变换电路的直流端的正负极分别通过分接开关 I与分接开关 Π 与站内分段母线和旁路母线连接； 其正极与所述分段母线连接时，通过所述开关 I中的单相开关 PA、 单相开关 PB和单相开关 PC分别与所述分段母线的三相相 连； 其负极与所述旁路母线连接时， 通过所述开关 Π中的单相开关 NA、 单相开 关 NB和单相开关 NC分别与所述旁路母线的三相对应相连。
8、 如权利要求 1所述的不停电直流融冰装置， 其特征在于， 所述谐振电路 II包 括串联的电感和电容。
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