阅读说明：本技术 一种站间通讯故障时三端混合直流阀组故障退出方法 (Method for quitting fault of three-terminal hybrid direct-current valve bank during inter-station communication fault ) 是由 黄剑湘 杨涛 付天乙 鞠翔 龙磊 刘航 李晓霞 韩建伟 朱旭东 李少森 陈诺 于 2019-11-18 设计创作，主要内容包括：本发明涉及特高压多端混合直流输电故障处理的领域,具体而言,涉及一种站间通讯故障时三端混合直流阀组故障退出方法。整流侧LCC站的一个阀组发生故障极停运后,应确保逆变侧定功率VSC站先极停运,逆变侧定直流电压VSC站最后停运,这样才能确保各站退出时,直流电压能维持稳定,避免直流系统发生振荡,直流系统失去稳定。在三端站间通讯故障下,阀组故障退出时,对应站均采用极停运的方法,可以有效避免故障阀组闭锁后非故障阀组由于过压造成保护再次动作。LCC站的阀组故障,在整流侧极停运后,采用低电流闭锁方法可以确保逆变侧定直流功率VSC站和逆变侧定直流电压VSC站先后平稳闭锁,有效避免VSC站发生失控。(The invention relates to the field of extra-high voltage multi-terminal hybrid direct-current transmission fault processing, in particular to a fault quitting method of a three-terminal hybrid direct-current valve bank during inter-station communication fault. A valves of rectification side LCC station breaks down and extremely shuts down the back, should ensure that contravariant side decides power VSC station extremely shutdown earlier, and contravariant side decides direct current voltage VSC station and stops down at last, just so can ensure that when each station withdraws from, direct current voltage can remain stable, avoids direct current system to take place the oscillation, and direct current system loses stably. Under the communication fault between the three terminals, when the valve group fault exits, the corresponding stations all adopt the extreme shutdown method, so that the protection action again caused by overvoltage on the non-fault valve group after the fault valve group is locked can be effectively avoided. The valve group fault of the LCC station can ensure that the inversion side fixed direct current power VSC station and the inversion side fixed direct current voltage VSC station are stably locked successively by adopting a low current locking method after the rectification side is extremely stopped, and the condition that the VSC station is out of control is effectively avoided.)

1. A three-terminal hybrid direct-current valve group fault exit method during inter-station communication fault is disclosed, wherein a three-terminal hybrid direct-current transmission system comprises an LCC transmitting terminal station and two VSC receiving terminal stations; the two VSC receiving end stations are respectively a fixed direct-current voltage VSC receiving end station and a fixed direct-current power VSC receiving end station; each pole of the LCC sending end station comprises two LCC converter valve groups connected in series; each pole of the constant direct-current voltage VSC receiving end station and the constant direct-current power VSC receiving end station comprises two MMC converter valve groups which are connected in series; the method is characterized in that: the following three valve group fault exit conditions are provided under the condition of communication fault between three stations:

A. when a valve bank fault exits at the LCC sending end station:

step 1: if the valve bank protection sends an emergency stop command, the failed valve bank immediately shifts the phase, and simultaneously sends a protective locking command to the other valve bank, and the other valve bank immediately shifts the phase after receiving the protective locking command of the valve bank; the fault valve group converts the valve group emergency shutdown command into an extreme emergency shutdown command, and the valve group is extremely shutdown after 20 ms;

if the valve group protection sends a locking pulse command, the fault valve group is locked immediately, and simultaneously sends a protective locking command to the other valve group of the local pole, and the other valve group receives the protective locking command of the local valve group and immediately shifts the phase; the fault valve group converts the valve group protective locking trigger pulse command into an extreme emergency shutdown command, and the extreme emergency shutdown command is carried out after 20 ms;

step 2: after the LCC sending end station is extremely stopped, the fixed direct current power VSC receiving end station maintains the direct current power, and the voltage of a direct current port is reduced; when the voltage of a port of a constant direct-current voltage VSC receiving end station is larger than the voltage of a direct-current port of a constant direct-current power VSC receiving end station, the constant direct-current voltage VSC receiving end station transmits power back to the constant direct-current power VSC receiving end station;

and step 3: configuring a minimum direct-current voltage reference value limit value of the valve group operation and maximum feedback power limit values of two VSC receiving end stations when communication faults of a fixed direct-current power VSC receiving end station and the fixed direct-current voltage VSC receiving end station occur;

and 4, step 4: setting minimum current locking logic of a constant direct-current voltage VSC receiving terminal; when the actual current of the VSC receiving terminal station with constant direct current power is less than I _ SET, the pole is stopped by the direct current low-current locking action after T1 is delayed, and the pole quitting is finished;

and 5: when the actual current of the VSC receiving terminal is less than I _ SET, the pole is stopped by the direct-current low-current locking action after T2 is delayed, and the pole quitting is finished;

B. when a valve bank fault of a fixed direct-current voltage VSC receiving end station exits:

step 1: the fault valve group immediately locks a trigger pulse and simultaneously sends a zero pressure control command to the other valve group, the fault valve group converts the valve group emergency shutdown command into an extreme emergency shutdown command, the valve group is extremely shutdown after 20ms, and the extreme exit is completed;

step 2: if the valve group of the fixed direct current power VSC receiving end station does not have a fault, the direct current system is maintained in the constant current control of the LCC sending end station; determining the direct current power VSC receiving end station to continuously control the direct current power;

if the valve bank of the fixed direct current power VSC receiving end station fails; the fixed direct current power VSC receives a locking trigger pulse of the terminal station and simultaneously sends a zero pressure control instruction to enable the other valve group of the local pole to control zero pressure; the fault valve group converts the valve group emergency shutdown command into an extreme emergency shutdown command, and the valve group is extremely shutdown after 20 ms;

and step 3: increasing the direct-current voltage of the LCC sending end station to a voltage control reference value, and enabling the LCC sending end station to enter constant voltage control and run in no-load;

and 4, step 4: c, the LCC sending end station stops running with low direct current, the LCC sending end station stops running with extreme, and the LCC sending end station stops running with three stations;

C. when a valve bank fault of a fixed direct current power VSC receiving end station exits:

step 1: the fault valve group immediately locks a trigger pulse and simultaneously sends a zero pressure control command to the other valve group, the fault valve group converts the valve group emergency shutdown command into an extreme emergency shutdown command, the valve group is extremely shutdown after 20ms, and the extreme exit is completed;

step 2: if the valve group of the fixed direct-current voltage VSC receiving end station does not have a fault, the direct-current system is maintained in the constant current control of the LCC sending end station; the fixed direct-current voltage VSC receiving terminal station continuously controls the direct-current voltage;

if the valve bank of the fixed direct-current voltage VSC receiving end station fails; the constant direct-current voltage VSC receives a terminal station locking trigger pulse and simultaneously sends a zero pressure control instruction to enable the other valve group of the current pole to control zero pressure; the fault valve group converts the valve group emergency shutdown command into an extreme emergency shutdown command, and the valve group is extremely shutdown after 20 ms;

and step 3: increasing the direct-current voltage of the LCC sending end station to a voltage control reference value, and enabling the LCC sending end station to enter constant voltage control and run in no-load;

and 4, step 4: and C, the LCC sending end station stops running at low direct current, the LCC sending end station stops running at an extreme, and the LCC sending end station stops running at three stations.

2. The method for exiting the fault of the three-terminal hybrid direct-current valve bank during the inter-station communication fault as claimed in claim 1, wherein the method comprises the following steps: setting the minimum direct-current voltage limit value of a fixed direct-current voltage VSC receiving end station within the range of 0.6-0.7 p.u.; setting the maximum back transmission power limit value of a fixed direct-current voltage VSC receiving end station within the range of 0.05-0.06 p.u.; the setting range of the I _ SET is 0.05-0.07 p.u.; the value range of T1 is 120-150 s, and the value range of T2 is 0.5-1 s greater than that of T1; the value range of the voltage control reference value is 1.03-1.04 p.u.

3. The method for quitting the fault of the three-terminal hybrid direct-current valve bank during the inter-station communication fault as claimed in claim 2, wherein the method comprises the following steps: i _ SET is 0.07 p.u.; t1 is 120 s; t2 was 120.5 s.

4. The method for quitting the fault of the three-terminal hybrid direct-current valve bank during the inter-station communication fault as claimed in claim 2, wherein the method comprises the following steps: and when the two VSC receiving end stations stop running, the actual current value of the LCC sending end station is less than I _ SET, the direct-current low-current locking action stops running after the delay time is 15-20 s, and the three-station electrode stops running.

5. The method for exiting the fault of the three-terminal hybrid direct-current valve bank during the inter-station communication fault as claimed in claim 1, wherein the method comprises the following steps: MMC transverter valves are formed by half-bridge submodule piece and full-bridge submodule piece mixture, and the component proportion of full-bridge submodule piece and half-bridge submodule piece is not less than 50%.

6. The method for exiting the fault of the three-terminal hybrid direct-current valve bank during the inter-station communication fault as claimed in claim 1, wherein the method comprises the following steps: each converter valve bank is provided with a bypass switch Q93, a bypass isolation knife switch Q3, an anode isolation switch Q2 and a cathode isolation switch Q1.

7. The method for exiting the fault of the three-terminal hybrid direct-current valve bank during the inter-station communication fault as claimed in claim 1, wherein the method comprises the following steps: each pole is provided with a pole bus isolating switch Q9 and a high-speed neutral bus switch HSNBS; the VSC receiving end station is also provided with a high-speed parallel switch HSS.

Technical Field

The invention relates to the field of extra-high voltage multi-terminal hybrid direct-current transmission fault processing, in particular to a fault quitting method of a three-terminal hybrid direct-current valve bank during inter-station communication fault.

Background

The ultra-high voltage three-terminal hybrid direct-current transmission technology is a new power technology, only one ultra-high voltage three-terminal hybrid direct-current transmission project in China is in construction in the world at present, and no ultra-high voltage three-terminal hybrid direct-current transmission project is put into operation.

In an extra-high voltage three-terminal hybrid direct-current transmission project, a transmitting terminal station S1 adopts a power grid commutation converter-based LCC-HVDC, and a receiving terminal station S2 and a receiving terminal station S3 adopt a hybrid direct-current transmission system which is based on a modular multilevel converter MMC-HVDC and operates in parallel at three terminals.

When the communication between stations is normal and the valve group is failed to exit, the converter station where the failed valve group is located can quickly transmit a valve group protection exit instruction to the other two stations, and the three stations can quickly and safely realize the protection exit of the valve group through the sequence control and the coordination of the voltage controller and the current controller.

Under the condition of communication faults between stations, data interaction between the three-terminal control protection systems cannot be carried out, and the original direct-current control protection function cannot finish the coordination quitting of the valve bank between the three stations. For a conventional LCC extra-high voltage three-terminal direct current system, when one converter station valve group fails to exit in inter-station communication failure, the other two stations respectively exit one valve group through direct current low voltage protection 27DC action under the regulation of respective voltage and current controllers. However, for mixed three-terminal direct current adopting LCC and MMC, after one valve bank of the LCC station at the rectification side is locked, the direct current voltage can still be controlled to be about 800kV by the inverter station fixed direct current voltage VSC station, and therefore the non-fault valve bank can not be overvoltage guaranteed only by actively stopping the operation electrode when the valve bank has a fault. For the valve group faults of the VSC station, the fault characteristics of the direct current system are different, the abnormal phenomena of direct current voltage, sudden change of direct current, long-time oscillation and the like easily occur, and even the whole direct current system is unstable. Therefore, the research on a valve group fault exit method under the condition of communication fault is a key technology and a difficulty of an extra-high voltage three-terminal hybrid direct current control protection system.

Disclosure of Invention

The invention aims to provide a method for quitting the fault of a three-terminal hybrid direct-current valve group during the inter-station communication fault, which can ensure that a current converter is safely quitted, and simultaneously control the influence on the direct-current operation within the minimum range, and ensure the safe and stable operation of a direct-current transmission system.

The embodiment of the invention is realized by the following steps:

a three-terminal hybrid direct-current valve group fault exit method during inter-station communication fault is disclosed, wherein a three-terminal hybrid direct-current transmission system comprises an LCC transmitting terminal station and two VSC receiving terminal stations; the two VSC receiving end stations are respectively a fixed direct-current voltage VSC receiving end station and a fixed direct-current power VSC receiving end station; the LCC sending terminal station comprises two LCC converter valve banks which are connected in series; the constant direct-current voltage VSC receiving end station and the constant direct-current power VSC receiving end station respectively comprise two MMC converter valve groups which are connected in series; the method is characterized in that: the following three valve group fault exit conditions are provided under the condition of communication fault between three stations:

A. when a valve bank fault exits at the LCC sending end station:

step 1: if the valve bank protection sends an emergency stop command, the failed valve bank immediately shifts the phase, and simultaneously sends a protective locking command to the other valve bank, and the other valve bank immediately shifts the phase after receiving the protective locking command of the valve bank; the fault valve group converts the valve group emergency shutdown command into an extreme emergency shutdown command, and the valve group is extremely shutdown after 20 ms;

if the valve group protection sends a locking pulse command, the fault valve group is locked immediately, and simultaneously sends a protective locking command to the other valve group of the local pole, and the other valve group receives the protective locking command of the local valve group and immediately shifts the phase; the fault valve group converts the valve group protective locking trigger pulse command into an extreme emergency shutdown command, and the extreme emergency shutdown command is carried out after 20 ms;

step 2: after the LCC sending end station is extremely stopped, the voltage of a direct current port is reduced by the fixed direct current power VSC receiving end station; when the voltage of a port of a fixed direct-current voltage VSC receiving end station is larger than the voltage of a direct-current port of a fixed direct-current power VSC receiving end station, the fixed direct-current voltage VSC receiving end station sends back power to the fixed direct-current power VSC receiving end station;

and step 3: configuring a minimum direct current voltage reference value limit value UREF-MIN when communication faults of a fixed direct current power VSC receiving end station and the fixed direct current voltage VSC receiving end station occur, and configuring a maximum feedback power limit value PMAX of the fixed direct current voltage VSC receiving end station and the fixed direct current power VSC receiving end station;

and 4, step 4: setting minimum current locking logic of a constant direct-current voltage VSC receiving terminal; when the actual current of the VSC receiving terminal station with constant direct current power is less than I _ SET, the pole is stopped by the direct current low-current locking action after T1 is delayed, and the pole quitting is finished;

and 5: when the actual current of the VSC receiving terminal is less than I _ SET, the pole is stopped by the direct-current low-current locking action after T2 is delayed, and the pole quitting is finished;

B. when a valve bank fault of a fixed direct-current voltage VSC receiving end station exits:

step 1: the fault valve group immediately locks a trigger pulse and simultaneously sends a zero pressure control command to the other valve group, the fault valve group converts the valve group emergency shutdown command into an extreme emergency shutdown command, the valve group is extremely shutdown after 20ms, and the extreme exit is completed;

step 2: if the valve group of the fixed direct current power VSC receiving end station does not have a fault, the direct current system is maintained in the constant current control of the LCC sending end station; determining the direct current power VSC receiving end station to continuously control the direct current power;

if the valve bank of the fixed direct current power VSC receiving end station fails; the fixed direct current power VSC receives a locking trigger pulse of the terminal station and simultaneously sends a zero pressure control instruction to enable the other valve group of the local pole to control zero pressure; the fault valve group converts the valve group emergency shutdown command into an extreme emergency shutdown command, and the valve group is extremely shutdown after 20 ms;

and step 3: increasing the direct-current voltage of the LCC sending end station to a voltage control reference value, and enabling the LCC sending end station to enter constant voltage control and run in no-load;

and 4, step 4: c, the LCC sending end station stops running with low direct current, the LCC sending end station stops running with extreme, and the LCC sending end station stops running with three stations;

C. when a valve bank fault of a fixed direct current power VSC receiving end station exits:

step 1: the fault valve group immediately locks a trigger pulse and simultaneously sends a zero pressure control command to the other valve group, the fault valve group converts the valve group emergency shutdown command into an extreme emergency shutdown command, the valve group is extremely shutdown after 20ms, and the extreme exit is completed;

step 2: if the valve group of the fixed direct-current voltage VSC receiving end station does not have a fault, the direct-current system is maintained in the constant current control of the LCC sending end station; the fixed direct-current voltage VSC receiving terminal station continuously controls the direct-current voltage;

if the valve bank of the fixed direct-current voltage VSC receiving end station fails; the constant direct-current voltage VSC receives a terminal station locking trigger pulse and simultaneously sends a zero pressure control instruction to enable the other valve group of the current pole to control zero pressure; the fault valve group converts the valve group emergency shutdown command into an extreme emergency shutdown command, and the valve group is extremely shutdown after 20 ms;

and step 3: increasing the direct-current voltage of the LCC sending end station to a voltage control reference value U _ LCC _ REF, and enabling the LCC sending end station to enter constant voltage control and run in no-load;

and 4, step 4: and C, the LCC sending end station stops running at low direct current, the LCC sending end station stops running at an extreme, and the LCC sending end station stops running at three stations.

Further, the setting range of the UREF _ MIN is 0.6-0.7 p.u.; the setting range of PMAX is 0.05-0.06 p.u.; the setting range of the I _ SET is 0.05-0.07 p.u.; the value range of T1 is 120-150 s, and the value of T2 is 0.5-1 s more than that of T1; the value range of U _ LCC _ REF is 1.03-1.04 p.u.

Further, I _ SET is 0.07 p.u.; t1 is 120 s; t2 was 120.5 s.

Further, when the poles of the two VSC receiving end stations are both stopped, the actual current value of the LCC sending end station is less than I _ SET, the poles are stopped by the direct-current low-current locking action after the delay time is 15-20 s, and the poles of the three stations are stopped.

Further, the MMC transverter valve bank is formed by mixing a half-bridge submodule and a full-bridge submodule, and the proportion of the full-bridge submodule and the half-bridge submodule is not lower than 50%.

Further, each converter valve group is provided with a bypass switch Q93, a bypass isolation knife switch Q3, an anode isolation switch Q2 and a cathode isolation switch Q1.

Further, each pole is provided with a pole bus isolating switch Q9 and a high-speed neutral bus switch HSNBS; the VSC receiving end station is also provided with a high-speed parallel switch HSS.

The invention has the beneficial effects that:

under the condition of communication failure among the three terminals, the invention provides that the extra-high voltage three-terminal hybrid direct-current series valve banks are all in an unlocked state, and when the valve banks fail to exit, the corresponding stations all adopt an extreme shutdown method, so that the problem that the non-failed valve banks are protected to act again due to overvoltage after the failed valve banks are locked can be effectively avoided. Meanwhile, aiming at the characteristics of the ultra-high voltage three-terminal mixed direct current, the invention designs a direct current low-current locking method which comprises the following steps: for the valve group fault of the rectification side LCC sending end station, after the rectification side pole is stopped, the inversion side fixed direct current power VSC receiving end station and the inversion side fixed direct current voltage VSC receiving end station can be ensured to be stably locked successively, and the condition that the VSC receiving end station is out of control is effectively avoided; meanwhile, after a valve group of a VSC receiving end station is extremely stopped due to fault, the other VSC receiving end station also has the working condition after the valve group is extremely stopped due to fault, the rectification side can be locked by low current, the LCC sending end station on the rectification side is prevented from long-time no-load operation, and the impact on the whole direct current system is reduced while the converter is guaranteed to safely exit.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

FIG. 1 is a schematic diagram of a connection mode of a series connection double-valve-group extra-high voltage three-terminal hybrid direct-current power transmission system;

FIG. 2 is a circuit diagram of a transmitting LCC type converter 6 ripple converter;

fig. 3 is a detailed circuit diagram of the ripple converter of the transmitting-end LCC type converter 12;

fig. 4 is a simplified circuit diagram of a ripple converter of the transmitting-end LCC type converter 12;

FIG. 5 is a diagram of a receive-side hybrid MMC circuit configuration;

FIG. 6 is a schematic diagram of half-bridge sub-modules of a receive-side hybrid MMC circuit;

FIG. 7 is a schematic diagram of a full bridge sub-module of the receiving-side hybrid MMC circuit;

fig. 8 is a flowchart of a failure exit of a valve group of an LCC sending end station according to an embodiment of the present invention;

fig. 9 is a flowchart of a fault exit of a valve block of a constant direct-current voltage VSC receiving terminal according to an embodiment of the present invention;

fig. 10 is a flowchart of a failure exit of a constant dc power VSC receiving end station valve group according to an embodiment of the present invention;

fig. 11 is a schematic diagram of a VSC receiving terminal dc low current blocking logic according to an embodiment of the present invention;

fig. 12 is a schematic diagram of a low-current blocking logic of the LCC transmitting station according to an embodiment of the present invention.

Icon: the system comprises a 1-LCC sending end station, an 11-LCC converter valve bank, a 2-VSC receiving end station and a 21-MMC converter valve bank.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.

Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.