阅读说明：本技术 一种特高压直流多馈入系统换相失败预防控制方法及系统 (Method and system for preventing and controlling commutation failure of extra-high voltage direct current multi-feed-in system ) 是由 饶宇飞 姚伟 李程昊 王骅 赵华 方舟 高昆 刘芳冰 谭阳琛 张伟晨 于 2019-10-31 设计创作，主要内容包括：本申请涉及一种特高压直流多馈入系统换相失败预防控制方法及系统,在交流系统发生故障后,距离交流故障点电气距离较近的逆变阀组的换相失败预防控制提前触发较大,可能导致距离交流故障点电气距离较远的逆变阀组发生换相失败。本申请的采用协调控制的方式,根据故障远区逆变阀组的关断角下降值自适应地调节故障近区逆变阀组的换相失败预防协调控制输出,从而达到避免故障远区逆变阀组发生换相失败的效果。(The application relates to a method and a system for preventing and controlling phase change failure of an extra-high voltage direct current multi-feed-in system. The method and the device adopt a coordinated control mode, and adaptively adjust the commutation failure prevention coordinated control output of the fault near-zone inversion valve bank according to the turn-off angle drop value of the fault far-zone inversion valve bank, so that the effect of avoiding the commutation failure of the fault far-zone inversion valve bank is achieved.)

1. A method for preventing and controlling commutation failure of an extra-high voltage direct current multi-feed-in system is characterized by comprising the following steps:

step 1, when an alternating current power grid fails, obtaining real-time measured values of turn-off angles of all inverter valve banks of a remote direct current system at a fault point;

step 2, subtracting the real-time measured value of the turn-off angle from the turn-off angle of each inverter valve group in stable operation to obtain a turn-off angle difference value corresponding to each inverter valve group;

step 3, taking the maximum value of the difference values of the turn-off angles, and selecting a self-adaptive commutation failure prevention control coefficient according to the maximum value;

step 4, acquiring the effective values of the voltage of the commutation bus during the actual operation of all the inversion valve groups, comparing the effective values with the effective values of the voltage of the commutation bus during the stable operation, judging whether the voltage drop condition of the alternating current power grid at the inversion side of the inversion valve group in the region close to the fault point is the most serious, and if so, entering step 5; otherwise, entering a step 8;

step 5, acquiring instantaneous values of the voltage of the current conversion bus when all the inverter valve banks actually operate, performing real-time fault detection on each direct current system inverter valve bank, and calculating independent trigger angle phase shift of each direct current system inverter valve bank;

step 6, judging whether the direct current system commutation failure prevention control is started due to voltage drop according to the trigger angle phase shift quantity, if so, entering step 7, otherwise, entering step 8;

step 7, selecting the adaptive commutation failure prevention control coefficient in the step 3, starting adaptive commutation failure prevention coordination control, and realizing the early triggering of the commutation failure prevention control on the inverter valve group in the near region of the fault point;

and 8, selecting a commutation failure prevention control coefficient when the inverter valve bank operates stably, and realizing the early triggering of the commutation failure prevention control on the inverter valve bank in the region close to the fault point.

2. The method according to claim 1, wherein in step 3, the determining of the adaptive commutation failure prevention control coefficient specifically comprises:

if the maximum value of the off-angle difference is greater than 5 electrical angles, the self-adaptive commutation failure prevention control coefficient is 0.05;

if the maximum value of the off-angle difference is greater than 2.5 electrical degrees and less than 5 electrical degrees, the adaptive commutation failure prevention control coefficient is 0.65;

otherwise, the adaptive commutation failure prevention control coefficient remains 0.1.

3. The method for preventing and controlling the commutation failure of the extra-high voltage direct current multi-feed-in system according to claim 1, wherein the step 4 specifically comprises:

subtracting the effective value of the converting bus voltage when all the inverter valve groups stably operate from the effective value of the converting bus voltage when all the inverter valve groups actually operate to obtain a voltage effective value difference value;

and if the obtained voltage effective value difference of the adjacent inversion valve banks at the fault point is larger than the voltage effective value difference of all the inversion valve banks at the remote area at the fault point, judging that the voltage drop condition of the alternating current power grid at the inversion side of the adjacent inversion valve banks at the fault point is the most serious.

4. The method for preventing and controlling the commutation failure of the extra-high voltage direct current multi-feed-in system according to claim 1, wherein the step 6 specifically comprises:

monitoring the trigger angle phase shift quantity of each inverter valve group in real time;

when the trigger angle phase shift amount of any one inverter valve group is monitored to be changed, judging that the direct current system phase change failure prevention control starting is caused by voltage drop, otherwise, judging that the direct current system phase change failure prevention control starting is caused by no voltage drop.

5. The method according to claim 1, wherein in step 5, the real-time fault detection comprises asymmetric fault detection and symmetric fault detection.

6. The method according to claim 5, wherein in step 5, the asymmetric fault detection specifically comprises:

through the zero sequence voltage of the instantaneous value of the three-phase voltage of the current conversion bus of the inverter valve group of the direct current system, whether the alternating current system has an asymmetric fault or not is judged, namely:

if the zero sequence voltage satisfies 3U₀＝U_a+U_b+U_cAnd 3U is₀If the value is less than the set threshold value, judging that no asymmetric fault occurs; otherwise, judging that an asymmetric fault occurs;

in the formula, 3U₀For zero-sequence voltage, U, of instantaneous values of three-phase voltage of converter bus_a、U_b、U_cThe instantaneous values of phase A, phase B and phase C voltages of the commutation bus are respectively.

7. The method according to claim 5, wherein in step 5, the symmetric fault detection specifically comprises:

converting the instantaneous value of the three-phase voltage of a converter bus of an inverter valve group of a direct current system into a two-phase static coordinate system, and judging an alternating current fault according to the root mean square of the two-phase static coordinate, namely:

first, the root mean square of the two-phase stationary coordinates is calculated according to the following formula:

in the formula of U_αIs α phase coordinate, U, under a two-phase stationary coordinate system_βIs β phase coordinate, U, under a two-phase stationary coordinate system_αβIs U_αAnd U_βRoot mean square of (d);

if U is_αβIf the value is larger than the set threshold value, judging that no symmetric fault occurs; otherwise, judging that the symmetric fault occurs.

8. The utility model provides an extra-high voltage direct current multi-feed system commutation failure prevention control system which characterized in that includes:

the system comprises a shutdown angle difference measuring module, a fault point remote area direct current system and a fault point remote area direct current system, wherein the shutdown angle difference measuring module is used for acquiring real-time measured values of shutdown angles of all inverter valve banks of the fault point remote area direct current system, and subtracting the real-time measured values of the shutdown angles of all the inverter valve banks in stable operation from the real-time measured values of the shutdown angles to obtain corresponding shutdown angle differences of all the inverter valve banks;

the commutation failure prevention control coefficient selection module is used for selecting a self-adaptive commutation failure prevention control coefficient according to the maximum value in each turn-off angle difference value;

the voltage enabling module is used for judging whether the voltage drop condition of the alternating current power grid at the inversion side of the inversion valve bank in the region near the fault point is the most serious or not according to the effective value of the voltage of the inversion bus when all the inversion valve banks actually operate;

the commutation failure prevention control enabling module is used for carrying out real-time fault detection on each direct-current system inversion valve group according to the instantaneous value of the commutation bus voltage when all the inversion valve groups actually operate, and calculating the independent trigger angle phase shift quantity of each direct-current system inversion valve group;

the commutation failure prevention control enabling module is used for judging whether commutation failure prevention control starting of the direct current system is caused by voltage drop according to independent trigger angle phase shift quantities of the inverter valve groups of the direct current system;

and the coordination control module is used for starting self-adaptive commutation failure prevention control when the voltage drop condition of the self-inverting side alternating current system of the inverting valve bank in the near area of the fault point is the most serious and the direct current system commutation failure prevention control is started due to the voltage drop, selecting the self-adaptive commutation failure prevention control coefficient and triggering the commutation failure prevention control on the inverting valve bank in the near area of the fault point in advance.

9. The system of claim 8, wherein the voltage enabling module comprises:

the subtraction unit is used for subtracting the effective value of the converting bus voltage during the stable operation of all the inverter valve groups from the effective value of the converting bus voltage during the actual operation to obtain a voltage effective value difference value;

and the comparison unit is used for comparing the voltage effective value difference of the fault point near-region inversion valve bank with the voltage effective value difference of the fault point far-region inversion valve bank, and if the voltage effective value difference of the fault point near-region inversion valve bank is greater than the voltage effective value differences of all the inversion valve banks in the fault point far-region, the situation that the voltage drop of the alternating current power grid at the inversion side of the fault point near-region inversion valve bank is the most serious is judged.

10. The system of claim 8, wherein the commutation failure prevention control enabling module comprises:

the commutation failure prevention control enabling subunit is used for detecting the change condition of the phase shift quantity of the trigger angle and outputting a step signal when detecting that the phase shift quantity of the trigger angle changes;

the monostable trigger holding unit is used for monostable trigger holding after detecting a step signal sent by the commutation failure prevention control enabling subunit;

or logic unit, which is used to receive the output signal of the monostable trigger holding unit and judge whether there is voltage drop to cause the commutation failure of the DC system to prevent the control starting.

Technical Field

The application belongs to the technical field of power systems, particularly relates to direct-current power transmission, and particularly relates to a method and a system for preventing and controlling commutation failure of an extra-high voltage direct-current multi-feed-in system.

Background

In recent years, with the continuous development of new energy power generation technology, ultra-high voltage direct current transmission becomes a mature and reliable technology capable of economically realizing large-capacity and long-distance transmission of electric energy, and is beneficial to realizing efficient utilization of large energy bases and clean energy such as photovoltaic and wind power in China. With successive operation of direct current projects in China, a power grid structure with multiple direct current accesses to the same area appears. These direct currents, which are electrically close together, form a multi-infeed direct current transmission system together with the fed-in alternating current network.

In an extra-high voltage direct current multi-feed-in system, after an alternating current system fails, the phase change failure prevention control of an inverter valve bank which is electrically close to an alternating current fault point is triggered greatly in advance, and the inverter valve bank which is electrically far from the alternating current fault point may fail to change phase.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: in order to solve the problem that in the prior art, after an alternating current system fails, the phase change failure prevention control of an inverter valve bank which is electrically close to an alternating current fault point is triggered greatly in advance, and the phase change failure of the inverter valve bank which is electrically far away from the alternating current fault point is possibly caused, a method and a system for preventing and controlling the phase change failure of an extra-high voltage direct current multi-feed-in system are provided.

The technical scheme adopted by the invention for solving the technical problems is as follows:

the invention provides a method for preventing and controlling commutation failure of an extra-high voltage direct current multi-feed-in system, which comprises the following steps:

step 1, when an alternating current power grid fails, obtaining real-time measured values of turn-off angles of all inverter valve banks of a remote direct current system at a fault point;

step 2, subtracting the real-time measured value of the turn-off angle from the turn-off angle of each inverter valve group in stable operation to obtain a turn-off angle difference value corresponding to each inverter valve group;

step 3, taking the maximum value of the difference values of the turn-off angles, and selecting a self-adaptive commutation failure prevention control coefficient according to the maximum value;

step 4, acquiring the effective values of the voltage of the commutation bus during the actual operation of all the inversion valve groups, comparing the effective values with the effective values of the voltage of the commutation bus during the stable operation, judging whether the voltage drop condition of the alternating current power grid at the inversion side of the inversion valve group in the region close to the fault point is the most serious, and if so, entering step 5; otherwise, entering a step 8;

step 5, acquiring instantaneous values of the voltage of the current conversion bus when all the inverter valve banks actually operate, performing real-time fault detection on each direct current system inverter valve bank, and calculating independent trigger angle phase shift of each direct current system inverter valve bank;

step 6, judging whether the direct current system commutation failure prevention control is started due to voltage drop according to the trigger angle phase shift quantity, if so, entering step 7, otherwise, entering step 8;

step 7, selecting the adaptive commutation failure prevention control coefficient in the step 3, and carrying out early triggering of commutation failure prevention control on the inverter valve group in the region near the fault point;

and 8, selecting a commutation failure prevention control coefficient when the inverter valve bank operates stably, and triggering the inverter valve bank in the region near the fault point in advance for commutation failure prevention control.

Further, according to the extra-high voltage direct current multi-feed-in system commutation failure prevention control method provided by the first aspect of the present invention, in step 3, the determining of the adaptive commutation failure prevention control coefficient specifically includes:

if the maximum value of the off-angle difference is greater than 5 electrical angles, the self-adaptive commutation failure prevention control coefficient is 0.05;

if the maximum value of the off-angle difference is greater than 2.5 electrical degrees and less than 5 electrical degrees, the adaptive commutation failure prevention control coefficient is 0.65;

otherwise, the adaptive commutation failure prevention control coefficient remains 0.1.

Further, according to the extra-high voltage direct current multi-feed-in system commutation failure prevention control method provided by the first aspect of the present invention, step 4 specifically includes:

subtracting the effective value of the converting bus voltage when all the inverter valve groups stably operate from the effective value of the converting bus voltage when all the inverter valve groups actually operate to obtain a voltage effective value difference value;

and if the obtained voltage effective value difference of the adjacent inversion valve banks at the fault point is larger than the voltage effective value difference of all the inversion valve banks at the remote area at the fault point, judging that the voltage drop condition of the alternating current power grid at the inversion side of the adjacent inversion valve banks at the fault point is the most serious.

Further, according to the extra-high voltage direct current multi-feed-in system commutation failure prevention control method provided by the first aspect of the present invention, step 6 specifically includes:

monitoring the trigger angle phase shift quantity of each inverter valve group in real time;

when the trigger angle phase shift amount of any one inverter valve group is monitored to be changed, judging that the direct current system phase change failure prevention control starting is caused by voltage drop, otherwise, judging that the direct current system phase change failure prevention control starting is caused by no voltage drop.

Further, according to the extra-high voltage direct current multi-feed-in system commutation failure prevention control method provided by the first aspect of the present invention, in step 5, the real-time fault detection includes asymmetric fault detection and symmetric fault detection.

Further, according to the extra-high voltage direct current multi-feed-in system commutation failure prevention control method provided by the first aspect of the present invention, in step 5, the asymmetric fault detection specifically includes:

through the zero sequence voltage of the instantaneous value of the three-phase voltage of the current conversion bus of the inverter valve group of the direct current system, whether the alternating current system has an asymmetric fault or not is judged, namely:

if the zero sequence voltage satisfies 3U₀＝U_a+U_b+U_cAnd 3U is₀If the value is less than the set threshold value, judging that no asymmetric fault occurs; otherwise, judging that an asymmetric fault occurs;

in the formula, 3U₀For zero-sequence voltage, U, of instantaneous values of three-phase voltage of converter bus_a、U_b、U_cThe instantaneous values of phase A, phase B and phase C voltages of the commutation bus are respectively.

Further, according to the extra-high voltage direct current multi-feed-in system commutation failure prevention control method provided by the first aspect of the present invention, in step 5, the symmetric fault detection specifically includes:

converting the instantaneous value of the three-phase voltage of a converter bus of an inverter valve group of a direct current system into a two-phase static coordinate system, and judging an alternating current fault according to the root mean square of the two-phase static coordinate, namely:

first, the root mean square of the two-phase stationary coordinates is calculated according to the following formula:

in the formula of U_αIs α phase coordinate, U, under a two-phase stationary coordinate system_βIs β phase coordinate, U, under a two-phase stationary coordinate system_αβIs U_αAnd U_βRoot mean square of (d);

if U is_αβIf the value is larger than the set threshold value, judging that no symmetric fault occurs; otherwise, judging that the symmetric fault occurs.

The invention provides a system for preventing and controlling commutation failure of an extra-high voltage direct current multi-feed-in system, which comprises:

the system comprises a shutdown angle difference measuring module, a fault point remote area direct current system and a fault point remote area direct current system, wherein the shutdown angle difference measuring module is used for acquiring real-time measured values of shutdown angles of all inverter valve banks of the fault point remote area direct current system, and subtracting the real-time measured values of the shutdown angles of all the inverter valve banks in stable operation from the real-time measured values of the shutdown angles to obtain corresponding shutdown angle differences of all the inverter valve banks;

the commutation failure prevention control coefficient selection module is used for selecting a self-adaptive commutation failure prevention control coefficient according to the maximum value in each turn-off angle difference value;

the voltage enabling module is used for judging whether the voltage drop condition of the alternating current power grid at the inversion side of the inversion valve bank in the region near the fault point is the most serious or not according to the effective value of the voltage of the inversion bus when all the inversion valve banks actually operate;

the commutation failure prevention control enabling module is used for carrying out real-time fault detection on each direct-current system inversion valve group according to the instantaneous value of the commutation bus voltage when all the inversion valve groups actually operate, and calculating the independent trigger angle phase shift quantity of each direct-current system inversion valve group;

the commutation failure prevention control enabling module is used for judging whether commutation failure prevention control starting of the direct current system is caused by voltage drop according to independent trigger angle phase shift quantities of the inverter valve groups of the direct current system;

and the coordination control module is used for starting self-adaptive commutation failure prevention control when the voltage drop condition of the self-inverting side alternating current system of the inverting valve bank in the near area of the fault point is the most serious and the direct current system commutation failure prevention control is started due to the voltage drop, selecting the self-adaptive commutation failure prevention control coefficient and triggering the commutation failure prevention control on the inverting valve bank in the near area of the fault point in advance.

Further, according to the extra-high voltage dc multi-feed-in system commutation failure prevention control system provided by the second aspect of the present invention, the voltage enabling module includes:

the subtraction unit is used for subtracting the effective value of the converting bus voltage during the stable operation of all the inverter valve groups from the effective value of the converting bus voltage during the actual operation to obtain a voltage effective value difference value;

and the comparison unit is used for comparing the voltage effective value difference of the fault point near-region inversion valve bank with the voltage effective value difference of the fault point far-region inversion valve bank, and if the voltage effective value difference of the fault point near-region inversion valve bank is greater than the voltage effective value differences of all the inversion valve banks in the fault point far-region, the situation that the voltage drop of the alternating current power grid at the inversion side of the fault point near-region inversion valve bank is the most serious is judged.

Further, according to the extra-high voltage dc multi-feed-in system commutation failure prevention control system provided by the second aspect of the present invention, the commutation failure prevention control enabling module includes:

the commutation failure prevention control enabling subunit is used for detecting the change condition of the phase shift quantity of the trigger angle and outputting a step signal when detecting that the phase shift quantity of the trigger angle changes;

the monostable trigger holding unit is used for monostable trigger holding after detecting a step signal sent by the commutation failure prevention control enabling subunit;

or logic unit, which is used to receive the output signal of the monostable trigger holding unit and judge whether there is voltage drop to cause the commutation failure of the DC system to prevent the control starting.

The invention has the beneficial effects that: the invention adaptively adjusts the commutation failure prevention coordination control output of the inverter valve bank in the near fault area according to the turn-off angle drop value of the inverter valve bank in the far fault area, thereby achieving the effect of avoiding the commutation failure of the inverter valve bank in the far fault area.

Drawings

The technical solution of the present application is further explained below with reference to the drawings and the embodiments.

FIG. 1 is a flow chart of a control method of an embodiment of the present application;

FIG. 2 is a block diagram of adaptive coordination control according to an embodiment of the present application;

fig. 3(a) is a comparison diagram of turn-off angles of the inverter valve bank 2 with or without coordination control after a near-zone ac system fault of the dc system 1 according to the embodiment of the present application;

fig. 3(b) is a comparison diagram of the turn-off angle of the inverter valve bank 3 with or without coordination control after a near-zone ac system fault of the dc system 1 according to the embodiment of the present application;

fig. 4(a) is a comparison diagram of the turn-off angle of the dc system 1 with or without coordination control after the near-zone ac system of the dc system 1 of the embodiment of the present application has a fault;

fig. 4(b) is a comparison graph of the dc power transmitted by the dc system 1 under the condition of no coordination control after the near-zone ac system of the dc system 1 has a fault according to the embodiment of the present application;

fig. 5 is a comparison graph of the dc power transmitted by the inverter valve banks 2 and 3 when there is no coordination control after the near ac system of the dc system 1 of the embodiment of the present application has failed.

Detailed Description

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.

The technical solutions of the present application will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.