CN114825356B

CN114825356B - Reactive exchange limit value optimization method, device, computer equipment and storage medium

Info

Publication number: CN114825356B
Application number: CN202210601761.7A
Authority: CN
Inventors: 黄聪; 郝志杰; 刘彬; 黄松强; 李晓霞; 胡付有; 孙上元; 张越帆; 王靓; 宋阳; 汤安琪; 田越宇; 夏武; 申狄秋; 王荣超; 尹忠葵; 张文鹏; 李洪坤; 荣军; 卢雯兴
Original assignee: Liuzhou Bureau of Extra High Voltage Power Transmission Co
Current assignee: Liuzhou Bureau of Extra High Voltage Power Transmission Co
Priority date: 2022-05-30
Filing date: 2022-05-30
Publication date: 2023-06-09
Anticipated expiration: 2042-05-30
Also published as: CN114825356A

Abstract

The application relates to a reactive exchange limit value optimization method, a reactive exchange limit value optimization device, computer equipment and a storage medium. The method comprises the following steps: acquiring bus voltage of an alternating current bus and direct current of a converter station under the condition that gear adjustment of a tap of a converter transformer is completed; determining the valve side voltage of the converter transformer according to the bus voltage and the gear after the adjustment is completed; determining the first active power consumed by the converter transformer according to the direct current and the valve side voltage; determining a second reactive power provided by the alternating current filter according to the bus voltage and the rated reactive power of the alternating current filter; according to the first reactive power and the second reactive power, determining a reactive exchange actual value between the converter station and the alternating current system; and adjusting an initial upper limit value and an initial lower limit value of the reactive exchange limit value according to the reactive exchange actual value, and correspondingly obtaining a target upper limit value and a target lower limit value. By adopting the method, the accuracy of the reactive exchange limit value can be improved, and the service life of equipment in the converter station is prolonged.

Description

Reactive exchange limit value optimization method, device, computer equipment and storage medium

Technical Field

The present application relates to the field of power technologies, and in particular, to a method, an apparatus, a computer device, and a storage medium for optimizing reactive exchange limits.

Background

The hvdc transmission system may also need to absorb a lot of reactive power and emit a lot of harmonics to the ac system while transmitting dc power. Therefore, a converter station of a high-voltage direct-current transmission system (except for a flexible direct-current transmission system) is provided with a plurality of groups of alternating-current filters for limiting the characteristic harmonic size in the converter station and providing reactive power required for converting direct-current power into alternating-current power. As reactive power occupies the capacity of an ac system, the larger the reactive power, the less the ac active power, and the lower the transmission efficiency. In order to reduce the reactive power transmitted by the ac system, the reactive power needs to be balanced in situ. When the converter station transmits different direct current power, the reactive power exchange between the converter station and the alternating current system is ensured to be within an allowable range by carrying out switching control on each group of alternating current filters in the converter station, so that the requirement of on-site balance of the reactive power is met.

Currently, when setting the reactive exchange limit between the converter station and the ac system, the ac system is usually default to be a strong ac system, the lower limit of the reactive exchange limit is usually set to-230, and the upper limit of the reactive exchange limit is usually set to 0, i.e. reactive power is not absorbed from the ac system, and a certain level of reactive support can be provided to the ac system. When a weak alternating current system (such as an alternating current system with a lack of reactive power or a low power level) is connected with the converter station, if the reactive power exchange limit value set in the above is adopted to realize the in-situ balance of the reactive power, frequent switching of equipment in the converter station is easily caused, and the service life of the equipment in the converter station is further reduced.

Disclosure of Invention

In view of the foregoing, it is desirable to provide a method, an apparatus, a computer device, and a storage medium for optimizing reactive exchange limits that can improve the service life of devices in a converter station.

In a first aspect, the present application provides a method for optimizing reactive exchange limits, applied to a power transmission system, the power transmission system comprising a converter station and an ac system, the converter station comprising a converter transformer, a converter transformer tap, an ac busbar and an ac filter, the method comprising:

acquiring bus voltage of the alternating current bus and direct current of the converter station under the condition that gear adjustment of the converter transformer tap is completed;

determining the valve side voltage of the converter transformer according to the bus voltage and the gear after the adjustment is completed;

determining a first passive power consumed by the converter transformer according to the direct current and the valve side voltage;

determining a second reactive power provided by the alternating current filter according to the bus voltage and the rated reactive power of the alternating current filter;

determining an actual value of reactive exchange between the converter station and the ac system according to the first reactive power and the second reactive power;

And adjusting an initial upper limit value and an initial lower limit value of the reactive exchange limit value according to the reactive exchange actual value, and correspondingly obtaining a target upper limit value and a target lower limit value.

In one embodiment, the adjusting the initial upper limit value and the initial lower limit value of the reactive exchange limit value according to the reactive exchange actual value correspondingly obtains a target upper limit value and a target lower limit value, including:

comparing the reactive exchange actual value with the initial upper limit value and the initial lower limit value respectively;

determining a candidate upper limit variation according to a difference value between the reactive exchange actual value and the initial upper limit value under the condition that the reactive exchange actual value is larger than the initial upper limit value;

under the condition that the reactive exchange actual value is smaller than the initial lower limit value, determining a candidate lower limit variation according to a difference value between the reactive exchange actual value and the initial lower limit value;

determining a plurality of candidate upper limit variable amounts and a plurality of candidate lower limit variable amounts of the converter station under different direct current conditions;

determining a maximum value of the plurality of candidate upper limit variation amounts as a target upper limit variation amount;

determining a maximum value of the plurality of candidate lower limit variation amounts as a target lower limit variation amount;

Determining the sum of the initial upper limit value and the target upper limit variation as a target upper limit value of the reactive exchange limit value;

and determining the difference between the initial lower limit value and the target lower limit variation as a target lower limit value of the reactive exchange limit value.

In one embodiment, the target upper limit variation and the target lower limit variation are less than or equal to 30MVar.

In one embodiment, the valve side voltage is calculated based on a first formula;

wherein the first formula comprises:

wherein ,U_di0 For the valve side voltage, U _{di0_norm} For the nominal value of the valve-side voltage, U _{ac_1} For the bus voltage, U _{ac_norm} T being the nominal value of the bus voltage _c Tap adjustment for said converter transformerAnd (5) a gear after completion.

In one embodiment, the first passive power is calculated based on a second formula;

wherein the second formula comprises:

wherein ,Q_conv For the first passive power, I _d And for the direct current, mu is a commutation overlap angle of the converter transformer, and alpha is a trigger angle of a converter valve of the converter transformer.

In one embodiment, the determining the second reactive power provided by the ac filter according to the bus voltage and the rated reactive power of the ac filter includes:

Obtaining rated values of the bus voltage, rated frequencies of the alternating current system and operating frequencies of the alternating current system;

and determining the second reactive power according to the bus voltage, the rated value of the bus voltage, the rated reactive power, the rated frequency and the operating frequency.

In one embodiment, the determining the actual value of the reactive exchange between the converter station and the ac system based on the first reactive power and the second reactive power comprises:

determining the number of the alternating current filters which the converter station is connected to under the condition of transmitting the direct current;

determining the actual value of the reactive exchange according to the product of the number of the alternating current filters and the second reactive power and the first reactive power.

In a second aspect, the present application also provides an optimization device for reactive exchange limits, applied to a power transmission system, the power transmission system including a converter station and an ac system, the converter station including a converter transformer, a converter transformer tap, an ac bus and an ac filter, the device comprising:

the data acquisition module is used for acquiring bus voltage of the alternating current bus and direct current of the converter station under the condition that gear adjustment of the converter transformer tap is completed;

The valve side voltage determining module is used for determining the valve side voltage of the converter transformer according to the bus voltage and the gear after the adjustment is completed;

the power determining module is used for determining first passive power consumed by the converter transformer according to the direct current and the valve side voltage;

the power determining module is further used for determining second reactive power provided by the alternating current filter according to the bus voltage and rated reactive power of the alternating current filter;

the actual value determining module is used for determining an actual value of reactive exchange between the converter station and the alternating current system according to the first reactive power and the second reactive power;

and the limit value optimization module is used for adjusting the initial upper limit value and the initial lower limit value of the reactive exchange limit value according to the reactive exchange actual value, and correspondingly obtaining a target upper limit value and a target lower limit value.

In a third aspect, the present application also provides a computer device for use in a power transmission system comprising a converter station and an ac system, the converter station comprising a converter transformer, a converter transformer tap, an ac busbar and an ac filter. The computer device comprises a memory storing a computer program and a processor which when executing the computer program performs the steps of:

In a fourth aspect, the present application also provides a computer readable storage medium for use in a power transmission system comprising a converter station and an ac system, the converter station comprising a converter transformer, a converter transformer tap, an ac busbar and an ac filter. The computer readable storage medium having stored thereon a computer program which when executed by a processor performs the steps of:

The reactive exchange limit value optimizing method, the reactive exchange limit value optimizing device, the computer equipment and the storage medium acquire the bus voltage of the alternating current bus and the direct current of the converter station under the condition that the gear adjustment of the tap of the converter transformer is completed; determining the valve side voltage of the converter transformer according to the bus voltage and the gear after the adjustment is completed; determining a first passive power consumed by the converter transformer according to the direct current and the valve side voltage; determining a second reactive power provided by the alternating current filter according to the bus voltage and the rated reactive power of the alternating current filter; determining an actual value of reactive exchange between the converter station and the ac system according to the first reactive power and the second reactive power; and adjusting an initial upper limit value and an initial lower limit value of the reactive exchange limit value according to the reactive exchange actual value, and correspondingly obtaining a target upper limit value and a target lower limit value. According to the characteristics that the reactive power provided by an alternating current filter can be influenced by the bus voltage in a converter station connected with a weak alternating current system and the power generation consumed by a converter transformer can be influenced by the gear change of a converter transformer tap, the gear and the bus voltage of the converter transformer tap are added as parameters when the reactive exchange limit value is optimized, so that the reactive exchange limit value is suitable for the converter station connected with the weak alternating current system, the continuous switching of the alternating current filter and the frequent adjustment of the converter transformer tap due to the inaccuracy of the reactive exchange limit value calculation are avoided, the service life of equipment in the converter station is prolonged, and the stability of the alternating current/direct current system is maintained.

Drawings

FIG. 1 is an application environment diagram of a reactive exchange limit optimization method in one embodiment;

FIG. 2 is a flow diagram of a method of optimizing reactive exchange limits in one embodiment;

FIG. 3 is a flow chart of a method of optimizing reactive exchange limits in another embodiment;

FIG. 4 is a block diagram of an optimization device for reactive exchange limits in one embodiment;

fig. 5 is an internal structural diagram of a computer device in one embodiment.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the present application will be further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the present application.

The method for optimizing the reactive exchange limit value can be applied to an application environment shown in fig. 1. The power transmission system comprises a converter station 100 in a direct current system and an alternating current system 200, the converter station 100 comprising a converter transformer 102, a converter transformer tap 104, an alternating current bus (not shown), an alternating current filter 106 and a control module 108. Where the consumers of reactive power of the converter station 100 are mainly the converter transformers 102 and the providers of reactive power are mainly the ac filters 106. The control module 108 provides reactive exchange limits between the converter station 100 and the ac system 200, and when the actual value of the reactive exchange between the converter station 100 and the ac system 200 exceeds the upper limit of the reactive exchange limits, reactive power needs to be absorbed from the ac system 200, at which point the control module 108 controls the input of a set of ac filters 106; if the actual value of the reactive exchange is below the lower value of the reactive exchange limit, reactive power needs to be transferred to the ac system 200, at which point the control module 108 controls the removal of a set of ac filters 106.

In the prior art, when setting the reactive exchange limit value, it is not considered that in a converter station connected with a weak ac system, the bus voltage of an ac bus, reactive power of reactive equipment and other electrical parameters are easy to fluctuate due to the change of running condition, power generation power or power consumption load, so that the set reactive exchange limit value is inaccurate. When the converter station is connected to a weak ac system, once the delivered dc power changes, the reactive power consumed by the converter transformer and the bus voltage both fluctuate, resulting in frequent switching of the ac filter 106 by the control module 108. If the reactive power exchange limit value is set unreasonably, the phenomenon of 'oscillation switching' of the ac filters 106 will occur, that is, after the control module 108 inputs a group of ac filters 106, the reactive power exchange actual value exceeds the lower limit value, the control module 108 immediately cuts off a group of ac filters 106, and after the cut-off reactive power exchange actual value exceeds the upper limit, the control module 108 inputs a group of ac filters 106, the ac filters 106 are frequently switched, so that the service life of the ac filters is rapidly reduced, and even the ac filters are easy to explode due to overheat of equipment. To ensure the safety of the equipment, the control module 108 typically needs to be put into operation again after cutting out a set of ac filters 106, for ten minutes after they have cooled down and discharged. Because the ac filter 106 provides reactive power, once the ac filter 106 fails to meet the reactive power consumption of the converter transformer 102 due to too small number, the control module 108 reduces the transmission of dc power for the stability of the ac system, resulting in a loss of generated power. Therefore, the influence of the weak ac system needs to be taken into account when calculating the reactive exchange limit between the converter station 100 and the ac system 200.

It should be appreciated that the strength of the ac system 200 is a relative concept that varies with seasonal variations, on-off variations in thermal and hydroelectric plants, and variations in electrical loads. In considering the impact of weak ac systems, it is necessary to find the intrinsic relation of reactive power within the converter station 100 and the electrical characteristics of the ac system 200 from physical phenomena, i.e. to quantify the weak ac system by building a reasonable mathematical model or expression. A large feature of weak ac systems is that the voltage varies with reactive power. For the converter station 100, the converter transformer tap 104 is used as an adjusting tool of the hvdc system, and by adjusting the trigger angle or the turn-off angle to operate at a reasonable angle value, the stability of the transmission power of the hvdc system is reduced due to external disturbance. Once the converter transformer tap 104 is adjusted, the valve side voltage of the converter transformer 102 must change, which is ultimately transferred to the reactive consumption of the converter transformer 102. Meanwhile, the ac filter 106 acts as a capacitive device that provides reactive power directly related to the level of the bus voltage of the ac bus. Therefore, a mathematical expression of the reactive power exchange limit value can be established according to the gear change of the converter transformer tap 104 and the change condition of the bus voltage, so that the reactive power exchange limit value is set more accurately, the operation requirement of a weak alternating current system can be met, and the purpose of dynamically adjusting the reactive power exchange limit value is achieved.

According to the embodiment of the application, in the calculation of the reactive power exchange limit value, the influence of the gear change of the converter transformer tap 104 on the reactive power consumed by the converter transformer 102 and the influence of the bus voltage of the alternating current bus on the reactive power in the converter station 100 are considered, and the mathematical expressions of the converter transformer tap, the bus voltage and the reactive power are established, so that the reactive power exchange limit value is more suitable for the converter station connected with a weak alternating current system, and the continuous switching of the alternating current filter 106 and the continuous adjustment of the converter transformer tap 104 caused by inaccurate calculation of the reactive power exchange limit value are avoided.

In one embodiment, as shown in fig. 2, a method for optimizing reactive exchange limit is provided, and the method is applied to the control module 108 in fig. 1 for illustration, and includes the following steps:

step 201, when the gear adjustment of the tap of the converter transformer is completed, the bus voltage of the ac bus and the dc current of the converter station are obtained.

The gear range of the tap of the converter transformer is generally-3 to 18, and the gear of the tap of the converter transformer can be different for different high-voltage direct current projects, but the tap of the converter transformer generally has positive values and negative values, and the positive value is more than 15.

Specifically, the bus voltage of the ac bus and the dc current of the converter station may be obtained by a real-time simulation system or by measuring operation data in the converter station. Wherein, the bus voltage can pass through formula U after the gear adjustment of the tap joint of the converter transformer is completed _{ac_1} ＝U _{ac_0} +△U _ac Calculated, where U _{ac_0} For bus voltage prior to tap adjustment of converter transformer DeltaU _ac For the change of bus voltage during the dynamic adjustment of the tap of the converter transformer, U _{ac_1} The bus voltage of the converter transformer tap after the first gear is adjusted up or down. The direct current delivered by the converter station will vary with the direct current power delivered by the converter station, and the value is generally 160A to 5000A.

Step 202, determining the valve side voltage of the converter transformer according to the bus voltage and the gear after the adjustment.

The converter transformer is a power transformer connected between the converter bridge and the alternating current system, can be connected with an alternating current bus by adopting the converter transformer, and provides a three-phase converter voltage with a neutral point which is not grounded for the converter bridge. The valve side voltage refers to the voltage at the output side of the transformer.

It will be appreciated that the valve side voltage of the converter transformer must change when the gear of the converter transformer tap changes. In a specific implementation, after the gear after the adjustment is completed and the bus voltage after the adjustment is completed are determined, the valve side voltage of the converter transformer can be calculated according to the bus voltage, the rated value of the valve side voltage of the converter transformer and the gear after the adjustment is completed.

Step 203, determining the first passive power consumed by the converter transformer according to the direct current and the valve side voltage.

Specifically, the first reactive power may be determined according to various manners, and in one example, the first reactive power may be calculated according to a product of the direct current and the valve side voltage, and in another example, the commutation overlap angle of the converter transformer and the trigger angle of the converter valve may be obtained, and the first reactive power is determined together according to the direct current, the valve side voltage, the commutation overlap angle, and the trigger angle. Since the situation of dynamic adjustment of the tap of the converter transformer and the change of the bus voltage are considered in calculation, compared with the prior art, the first reactive power consumed by the converter transformer is more accurate.

Step 204, determining a second reactive power provided by the alternating current filter according to the bus voltage and the rated reactive power of the alternating current filter.

The rated reactive power of the alternating current filter can be determined according to the type of the alternating current filter, and the second reactive power refers to reactive power provided by a group of alternating current filters in the converter station.

Specifically, the second reactive power may be determined according to a variety of manners, and in one example, the ratio of the second reactive power to the rated reactive power may be calculated according to the ratio of the bus voltage to the rated value of the bus voltage, the ratio of the actual operating frequency of the ac system to the rated frequency, and the second reactive power may be calculated according to the ratio and the rated reactive power.

Step 205, determining an actual value of reactive exchange between the converter station and the ac system according to the first reactive power and the second reactive power.

It should be understood that the first reactive power is the reactive power consumed by the converter transformer, the second reactive power is the reactive power provided by a set of ac filters, and the actual reactive exchange value between the converter station and the ac system can be calculated according to the total reactive power provided by a plurality of sets of ac filters in the converter station and the reactive power consumed by the converter transformer.

And step 206, adjusting the initial upper limit value and the initial lower limit value of the reactive exchange limit value according to the actual reactive exchange value, and correspondingly obtaining the target upper limit value and the target lower limit value.

Wherein the initial upper limit value of the reactive exchange limit value refers to a preset upper limit value, the initial lower limit value refers to a preset lower limit value, the lower limit value is generally set to-230, and the upper limit value is set to 0, and the reactive exchange limit value can meet the condition that the converter station does not absorb reactive power from the alternating current system and can provide a certain level of reactive support for the alternating current system. According to the method, the initial upper limit value and the initial lower limit value are adjusted according to the reactive power exchange actual value, so that the target upper limit value and the target lower limit value of the reactive power exchange limit value can be applied to a strong alternating current system and a weak alternating current system, and meanwhile, dynamic adjustment can be carried out by matching with the running mode change of the alternating current system, the safe and efficient running of the whole alternating current-direct current system is facilitated, the input use of additional reactive power equipment is reduced, and the construction cost of high-voltage direct current engineering is indirectly reduced.

According to the reactive exchange limit optimization method, according to the characteristics that the bus voltage can influence reactive power provided by an alternating current filter and the gear change of a converter transformer tap can influence power generation consumed by the converter transformer in a converter station connected with a weak alternating current system, the gear and the bus voltage of the converter transformer tap are added as parameters when the reactive exchange limit is optimized, so that the reactive exchange limit is suitable for the converter station connected with the weak alternating current system, continuous switching of the alternating current filter and frequent adjustment of the converter transformer tap due to inaccurate calculation of the reactive exchange limit are avoided, the service life of equipment in the converter station is prolonged, and the stability of the alternating current/direct current system is maintained.

In one embodiment, the step of adjusting the initial upper limit value and the initial lower limit value of the reactive exchange limit value according to the reactive exchange actual value, correspondingly obtaining a target upper limit value and a target lower limit value, includes:

comparing the reactive exchange actual value with an initial upper limit value and an initial lower limit value respectively; under the condition that the actual value of reactive power exchange is larger than the initial upper limit value, determining a candidate upper limit variation according to the difference value between the actual value of reactive power exchange and the initial upper limit value; under the condition that the actual value of reactive power exchange is smaller than the initial lower limit value, determining a candidate lower limit variation according to the difference value between the actual value of reactive power exchange and the initial lower limit value; determining a plurality of candidate upper limit variable amounts and a plurality of candidate lower limit variable amounts of the converter station under different direct current conditions; determining a maximum value of the plurality of candidate upper limit variation amounts as a target upper limit variation amount; determining the maximum value of the plurality of candidate lower limit variation amounts as a target lower limit variation amount; determining the sum of the initial upper limit value and the target upper limit variation as a target upper limit value of the reactive exchange limit value; and determining the difference between the initial lower limit value and the target lower limit variation as a target lower limit value of the reactive exchange limit value.

Specifically, when the reactive power exchange actual value is larger than the initial upper limit value, a difference between the reactive power exchange actual value and the initial upper limit value may be used as the candidate upper limit variation amount, or the candidate upper limit variation amount may be determined together from the margin of the weak ac system and the difference. In one example, assuming that the reactive exchange actual value is Qexp, the initial upper limit value is qexp_up, if Qexp > qexp_up, the candidate upper limit change amount Δqexp_up= |qexp_up-qexp| (1+10%) is a margin suitable for various weak ac systems.

When the reactive power exchange actual value is smaller than the initial lower limit value, a difference between the reactive power exchange actual value and the initial lower limit value may be used as the candidate lower limit variation, or the candidate lower limit variation may be determined together according to the margin of the weak ac system and the difference. In one example, assuming that the reactive exchange actual value is Qexp, the initial lower limit value is qexp_down, if Qexp > qexp_down, the candidate lower limit variation Δqexp_down= |qexp_down-qexp| (1+10%) is a margin suitable for various weak ac systems.

It should be appreciated that since the dc current is constantly changing when the converter station transmits each dc power, after the candidate upper limit variation and the candidate lower limit variation of one dc current are determined, a plurality of candidate upper limit variations and a plurality of candidate lower limit variations in the case of different dc currents may be determined in the same manner, and the maximum values Δqexp_up_max and Δqexp_down_max may be selected therefrom as the target upper limit variation and the target lower limit variation, respectively.

The target upper limit value of the reactive exchange limit value can be calculated by the formula qexp_up '=qexp_up+ [ delta ] qexp_up_max, and the target lower limit value of the reactive exchange limit value can be calculated by the formula qexp_down' =qexp_down- [ delta ] qexp_down_max.

It is emphasized that considering that weak ac systems are more sensitive to variations in reactive power, the range of the reactive exchange limit is not necessarily too large, and in one example, the values of the target upper limit variation and the target lower limit variation are not necessarily more than 30MVar, i.e. Δqexp_up_max is less than or equal to 30MVar, and Δqexp_down_max is less than or equal to 30MVar.

In the embodiment, the initial upper limit value and the initial lower limit value of the reactive exchange limit value are optimized, so that frequent switching of an alternating current filter and frequent adjustment of a tap of a converter transformer caused by disturbance fine adjustment of a direct current system can be effectively avoided, and the service life of equipment in a converter station is prolonged.

wherein the first formula comprises:

wherein ,U_di0 For valve side voltage, U _{di0_norm} For the nominal value of the valve-side voltage, U _{ac_1} Is the bus voltage, U _{ac_norm} For the nominal value of the bus voltage, T _c The gear is the gear after the tap of the converter transformer is adjusted.

According to the embodiment, by introducing the electrical parameter of the valve side voltage of the converter transformer, the physical phenomenon of how the fluctuation of the bus voltage affects the reactive power of the converter station is established, a detailed mathematical calculation process is established, so that a relation between the reactive exchange limit value and the bus voltage is established, and a theoretical calculation basis is provided for dynamic adjustment of the reactive exchange limit value.

In one embodiment, the first reactive power is calculated based on a second formula;

wherein the second formula comprises:

wherein ,Q_conv For the first passive power, U _di0 For valve side voltage, I _d And (3) taking the direct current as the current, wherein mu is the commutation overlap angle of the converter transformer, and alpha is the trigger angle of a converter valve of the converter transformer.

In this embodiment, the accuracy of the first active power is further improved due to factors such as the commutation overlap angle of the converter transformer and the trigger angle of the converter valve added when the first active power is calculated.

In one embodiment, determining the second reactive power provided by the ac filter based on the bus voltage and the rated reactive power of the ac filter includes: obtaining rated value of bus voltage, rated frequency of an alternating current system and operating frequency of the alternating current system; and determining the second reactive power according to the bus voltage, the rated value of the bus voltage, the rated reactive power, the rated frequency and the operating frequency.

Specifically, the second reactive power may be calculated based on a third formula, wherein the third formula comprises:

Q _filt ＝Q _{_norm} *(U _{ac_1} /U _{ac_norm} ) ² *(f/f _n )；

wherein ,Q_filt For the second reactive power, U _{ac_1} Is the bus voltage, U _{ac_norm} Is the rated value of bus voltage, f is the operating frequency, f _n For nominal frequency, Q _{_norm} Rated reactive power provided to a set of ac filters.

In the embodiment, the ac filter is considered as a capacitive device, the reactive power provided by the ac filter is directly related to the level of the bus voltage, and the parameter of the bus voltage is added when the second reactive power is calculated, so that the accuracy of the second reactive power is improved.

In one embodiment, determining the actual value of the reactive exchange between the converter station and the ac system from the first reactive power and the second reactive power comprises: determining the number of alternating current filters which are connected to the converter station under the condition of transmitting direct current; and determining the actual reactive exchange value according to the product of the number of the alternating current filters and the second reactive power and the first reactive power.

Specifically, the reactive exchange actual value may be calculated based on a fourth formula, wherein the fourth formula comprises:

Q _exp ＝2*Q _conv -N*Q _filt ；

wherein ,Q_exp For reactive exchange of actual values, Q _conv N is the first passive power, Q _filt For the second reactive power, N is the direct current I transmitted by the converter station _d The number of ac filters required to be put into operation.

According to the method and the device for determining the reactive power exchange actual value, the situation that a plurality of groups of alternating current filters exist in the converter station is considered, the reactive power exchange actual value is determined according to the first reactive power, the second reactive power and the number of the alternating current filters, and the calculation accuracy of the reactive power exchange actual value is improved.

In one embodiment, as shown in fig. 3, the method of optimizing reactive exchange limits may include the steps of:

step 301, obtaining a bus voltage of an alternating current bus and a direct current of a converter station when gear adjustment of a tap of a converter transformer is completed.

Step 302, determining the valve side voltage of the converter transformer according to the bus voltage and the gear after the adjustment.

Step 303, determining the first passive power consumed by the converter transformer according to the direct current and the valve side voltage.

Step 304, determining a second reactive power provided by the ac filter according to the bus voltage and the rated reactive power of the ac filter.

Step 305, determining an actual value of reactive exchange between the converter station and the ac system based on the first reactive power and the second reactive power.

And 306, comparing the reactive power exchange actual value with an initial upper limit value and an initial lower limit value respectively, determining a candidate upper limit variation according to the difference value between the reactive power exchange actual value and the initial upper limit value when the reactive power exchange actual value is larger than the initial upper limit value, and determining a candidate lower limit variation according to the difference value between the reactive power exchange actual value and the initial lower limit value when the reactive power exchange actual value is smaller than the initial lower limit value.

Step 307 determines a plurality of candidate upper limit variations and a plurality of candidate lower limit variations for the converter station in the case of different direct currents.

In step 308, the maximum value of the plurality of candidate upper limit variations is determined as the target upper limit variation, and the maximum value of the plurality of candidate lower limit variations is determined as the target lower limit variation.

Step 309, determining the sum of the initial upper limit value and the target upper limit variation as the target upper limit value of the reactive exchange limit value, and determining the difference between the initial lower limit value and the target lower limit variation as the target lower limit value of the reactive exchange limit value.

The converter station is operated at Id=2950A, the commutation overlap angle mu=19° =0.3316rad of the converter transformer, the trigger angle alpha=142.3° =2.48rad (the values of the commutation overlap angle and the trigger angle generally do not change with power variation), the converter transformer tap is in first gear, and the busbar voltage U is as follows _ac 542kV, put into 10 groups of alternating current filtersThe rated capacity of each group of alternating current filters is 168MVar, the tap of the converter transformer is adjusted by first gear, the bus voltage is changed by about 1kV, after the tap of the converter transformer is adjusted, the bus voltage is changed by 2kV, the frequency is not changed during the period, the initial lower limit value of the reactive exchange limit value is-230, and the initial upper limit value is 0, so the embodiment is described.

When the tap of the converter transformer is regulated from 1 level to 2 levels due to disturbance of the direct current system (the control module of the converter station maintains the stability of electrical parameters such as a trigger angle, a commutation overlap angle and the like by adjusting the tap of the converter transformer so that the converter valve can operate under the optimal working condition), the bus voltage is changed from 542kV to 544kV, namely U _{ac_0} ＝542kV，U _{ac_1} ＝544kV。

By a first formula

Calculating to obtain valve side voltage U of the converter transformer after the tap position of the converter transformer is regulated _di0 Is 273.76kV.

By a second formula

Calculating to obtain the first passive power Q consumed by the converter transformer after the adjustment is completed _conv 784.07MVar.

Through a third formula Q _filt ＝Q _{_norm} *(U _{ac_1} /U _{ac_norm} ) ² *(f/f _n ) After the bus voltage is calculated to change due to tap shift of the converter transformer, the second reactive power Q provided by each group of alternating current filters _filt 180.38MVar.

Through a fourth formula Q _exp ＝2*Q _conv -N*Q _filt Calculating to obtain the reactive exchange actual value Q of the converter station and the alternating current system _exp Is-235.66 MVar.

The control module will cut off a set of ac filters because the actual value of the reactive exchange is less than the initial lower limit value-230 MVar. However, for weak ac systems, when a set of ac filters is cut off, the reactive power change is large (about 168 MVar), the bus voltage will drop significantly (about 3 kV), and the reactive power provided by the ac filters in the converter station will decrease. Meanwhile, after the bus voltage is reduced, the direct current voltage and the valve side voltage of the converter station are reduced. To maintain dc power stable, the control module will turn down the converter transformer tap to increase the valve side voltage and dc voltage. At this time, the reactive power consumed by the converter transformer is increased, and on the premise that the reactive power provided by the alternating current filter is reduced as a whole, the reactive power exchange actual value is easily higher than the set initial upper limit value, so that frequent back and forth adjustment of the tap of the converter transformer and frequent switching and dead circulation of the alternating current filter are caused, safety accidents of burning due to overheat of equipment are caused, and stable operation of an alternating current-direct current system is also not facilitated.

Therefore, in the weak ac system, if the reactive exchange limit value can be optimized, for example, the initial lower limit value is adjusted to qexp_down= -230- (-230+235.66) × (1+10%) = -237 (integer), frequent switching or adjustment of reactive equipment such as ac filters and the like caused by disturbance fine adjustment of the dc system of the equipment in the converter station can be avoided, and the service life of the equipment is prolonged.

It should be understood that, although the steps in the flowcharts related to the above embodiments are sequentially shown as indicated by arrows, these steps are not necessarily sequentially performed in the order indicated by the arrows. The steps are not strictly limited to the order of execution unless explicitly recited herein, and the steps may be executed in other orders. Moreover, at least some of the steps in the flowcharts described in the above embodiments may include a plurality of steps or a plurality of stages, which are not necessarily performed at the same time, but may be performed at different times, and the order of the steps or stages is not necessarily performed sequentially, but may be performed alternately or alternately with at least some of the other steps or stages.

Based on the same inventive concept, the embodiment of the application also provides an optimization device for the reactive exchange limit value, which is used for realizing the optimization method of the reactive exchange limit value. The implementation of the solution provided by the device is similar to the implementation described in the above method, so the specific limitations in the embodiments of the optimizing device for reactive exchange limit value or values provided below can be referred to the limitations of the optimizing method for reactive exchange limit value hereinabove, and will not be repeated here.

In one embodiment, as shown in fig. 4, there is provided an optimizing apparatus of reactive exchange limit value applied to a power transmission system including a converter station and an ac system, the converter station including a converter transformer, a converter transformer tap, an ac bus and an ac filter, the optimizing apparatus of reactive exchange limit value including: a data acquisition module 401, a valve side voltage determination module 402, a power determination module 403, an actual value determination module 404, and a limit optimization module 405, wherein: the data acquisition module 401 is used for acquiring bus voltage of an alternating current bus and direct current of a converter station under the condition that gear adjustment of a converter transformer tap is completed; a valve side voltage determining module 402, configured to determine a valve side voltage of the converter transformer according to the bus voltage and the gear after the adjustment is completed; the power determining module 403 is configured to determine a first passive power consumed by the converter transformer according to the direct current and the valve side voltage; the power determining module 403 is further configured to determine a second reactive power provided by the ac filter according to the bus voltage and the rated reactive power of the ac filter; an actual value determining module 404, configured to determine an actual value of reactive exchange between the converter station and the ac system according to the first reactive power and the second reactive power; the limit value optimizing module 405 is configured to adjust an initial upper limit value and an initial lower limit value of the reactive exchange limit value according to the reactive exchange actual value, and correspondingly obtain a target upper limit value and a target lower limit value.

In one embodiment, the limit optimization module 405 is further configured to compare the reactive exchange actual value with an initial upper limit value and an initial lower limit value, respectively; under the condition that the actual value of reactive power exchange is larger than the initial upper limit value, determining a candidate upper limit variation according to the difference value between the actual value of reactive power exchange and the initial upper limit value; under the condition that the actual value of reactive power exchange is smaller than the initial lower limit value, determining a candidate lower limit variation according to the difference value between the actual value of reactive power exchange and the initial lower limit value; determining a plurality of candidate upper limit variable amounts and a plurality of candidate lower limit variable amounts of the converter station under different direct current conditions; determining a maximum value of the plurality of candidate upper limit variation amounts as a target upper limit variation amount; determining the maximum value of the plurality of candidate lower limit variation amounts as a target lower limit variation amount; determining the sum of the initial upper limit value and the target upper limit variation as a target upper limit value of the reactive exchange limit value; and determining the difference between the initial lower limit value and the target lower limit variation as a target lower limit value of the reactive exchange limit value.

In one embodiment, the valve side voltage determination module 402 is configured to calculate a valve side voltage based on a first formula; wherein the first formula comprises:

In one embodiment, the power determining module 403 is further configured to calculate a first passive power based on the second formula; wherein the second formula comprises:

wherein ,Q_conv For the first passive power, I _d And (3) taking the direct current as the current, wherein mu is the commutation overlap angle of the converter transformer, and alpha is the trigger angle of a converter valve of the converter transformer.

In one embodiment, the power determining module 403 is further configured to obtain a rated value of the bus voltage, a rated frequency of the ac system, and an operating frequency of the ac system; and determining the second reactive power according to the bus voltage, the rated value of the bus voltage, the rated reactive power, the rated frequency and the operating frequency.

In one embodiment, the actual value determining module 404 is further configured to determine the number of ac filters that the converter station accesses in the case of transmitting dc current; and determining the actual reactive exchange value according to the product of the number of the alternating current filters and the second reactive power and the first reactive power.

The various modules in the reactive exchange limit optimization device can be realized in whole or in part by software, hardware and a combination thereof. The above modules may be embedded in hardware or may be independent of a processor in the computer device, or may be stored in software in a memory in the computer device, so that the processor may call and execute operations corresponding to the above modules.

In one embodiment, a computer device is provided, which may be a terminal, and the internal structure of which may be as shown in fig. 4. The computer device includes a processor, a memory, a communication interface, a display screen, and an input device connected by a system bus. Wherein the processor of the computer device is configured to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage media. The communication interface of the computer device is used for carrying out wired or wireless communication with an external terminal, and the wireless mode can be realized through WIFI, a mobile cellular network, NFC (near field communication) or other technologies. The computer program, when executed by the processor, implements a method of optimizing reactive exchange limits. The display screen of the computer equipment can be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer equipment can be a touch layer covered on the display screen, can also be keys, a track ball or a touch pad arranged on the shell of the computer equipment, and can also be an external keyboard, a touch pad or a mouse and the like.

Those skilled in the art will appreciate that the structures shown in FIG. 4 are block diagrams only and do not constitute a limitation of the computer device on which the present aspects apply, and that a particular computer device may include more or less components than those shown, or may combine some of the components, or have a different arrangement of components.

In one embodiment, a computer device is provided comprising a memory and a processor, the memory having stored therein a computer program, the processor when executing the computer program performing the steps of:

under the condition that gear adjustment of a tap of the converter transformer is completed, bus voltage of an alternating current bus and direct current of a converter station are obtained;

determining the first active power consumed by the converter transformer according to the direct current and the valve side voltage;

according to the first reactive power and the second reactive power, determining a reactive exchange actual value between the converter station and the alternating current system;

In one embodiment, the processor when executing the computer program further performs the steps of:

the target upper limit variation and the target lower limit variation are less than or equal to 30MVar.

the valve side voltage is calculated based on a first formula; wherein the first formula comprises:

the first passive power is calculated based on a second formula; wherein the second formula comprises:

obtaining rated value of bus voltage, rated frequency of an alternating current system and operating frequency of the alternating current system; and determining the second reactive power according to the bus voltage, the rated value of the bus voltage, the rated reactive power, the rated frequency and the operating frequency.

determining the number of alternating current filters which are connected to the converter station under the condition of transmitting direct current; and determining the actual reactive exchange value according to the product of the number of the alternating current filters and the second reactive power and the first reactive power.

In one embodiment, a computer readable storage medium is provided having a computer program stored thereon, which when executed by a processor, performs the steps of:

In one embodiment, the computer program when executed by the processor further performs the steps of:

In one embodiment, a computer program product is provided comprising a computer program which, when executed by a processor, performs the steps of:

It should be noted that, user information (including but not limited to user equipment information, user personal information, etc.) and data (including but not limited to data for analysis, stored data, presented data, etc.) referred to in the present application are information and data authorized by the user or sufficiently authorized by each party.

Those skilled in the art will appreciate that implementing all or part of the above described methods may be accomplished by way of a computer program stored on a non-transitory computer readable storage medium, which when executed, may comprise the steps of the embodiments of the methods described above. Any reference to memory, database, or other medium used in the various embodiments provided herein may include at least one of non-volatile and volatile memory. The nonvolatile Memory may include Read-Only Memory (ROM), magnetic tape, floppy disk, flash Memory, optical Memory, high density embedded nonvolatile Memory, resistive random access Memory (ReRAM), magnetic random access Memory (Magnetoresistive Random Access Memory, MRAM), ferroelectric Memory (Ferroelectric Random Access Memory, FRAM), phase change Memory (Phase Change Memory, PCM), graphene Memory, and the like. Volatile memory can include random access memory (Random Access Memory, RAM) or external cache memory, and the like. By way of illustration, and not limitation, RAM can be in the form of a variety of forms, such as static random access memory (Static Random Access Memory, SRAM) or dynamic random access memory (Dynamic Random Access Memory, DRAM), and the like. The databases referred to in the various embodiments provided herein may include at least one of relational databases and non-relational databases. The non-relational database may include, but is not limited to, a blockchain-based distributed database, and the like. The processors referred to in the embodiments provided herein may be general purpose processors, central processing units, graphics processors, digital signal processors, programmable logic units, quantum computing-based data processing logic units, etc., without being limited thereto.

The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The above examples only represent a few embodiments of the present application, which are described in more detail and are not to be construed as limiting the scope of the present application. It should be noted that it would be apparent to those skilled in the art that various modifications and improvements could be made without departing from the spirit of the present application, which would be within the scope of the present application. Accordingly, the scope of protection of the present application shall be subject to the appended claims.

Claims

1. A method of optimizing reactive exchange limits for a power transmission system, the power transmission system comprising a converter station and an ac system, the converter station comprising a converter transformer, a converter transformer tap, an ac bus and an ac filter, the method comprising:

according to the reactive exchange actual value, an initial upper limit value and an initial lower limit value of a reactive exchange limit value are adjusted, and a target upper limit value and a target lower limit value are correspondingly obtained; the adjusting the initial upper limit value and the initial lower limit value of the reactive exchange limit value according to the reactive exchange actual value, correspondingly obtaining the target upper limit value and the target lower limit value of the reactive exchange limit value, includes:

2. The method of claim 1, wherein the obtaining the bus voltage of the ac bus comprises:

by formula U _{ac_1} = U _{ac_0} +△U _ac Calculating the bus voltage, wherein U _{ac_0} For the bus voltage prior to tap adjustment of the converter transformer, deltaU _ac For the change amount of bus voltage during the dynamic adjustment of the tap of the converter transformer, U _{ac_1} And (3) the bus voltage of the converter transformer tap after the first gear is regulated up or reduced.

3. The method of claim 2, wherein the target upper limit variation and the target lower limit variation are less than or equal to 30MVar.

4. A method according to any one of claims 1 to 3, wherein the valve side voltage is calculated based on a first formula;

wherein the first formula comprises:

；/>

wherein ,U_di0 For the valve side voltage, U _{di0_norm} For the nominal value of the valve-side voltage, U _{ac_1} For the bus voltage, U _{ac_norm} T being the nominal value of the bus voltage _c And (5) the gear after the tap of the converter transformer is adjusted.

5. The method of claim 4, wherein the first active power is calculated based on a second formula;

wherein the second formula comprises:

；

wherein ,

for the first passive power, I _d For the direct current, +.>

For the commutation overlap angle of the converter transformer +.>

And the trigger angle of a converter valve of the converter transformer.

6. The method of claim 1, wherein said determining the second reactive power provided by the ac filter based on the bus voltage and the rated reactive power of the ac filter comprises:

7. The method of claim 6, wherein said determining an actual value of reactive exchange between the converter station and the ac system based on the first reactive power and the second reactive power comprises:

8. An optimization device of reactive exchange limit values applied to a power transmission system, characterized in that the power transmission system comprises a converter station and an ac system, the converter station comprising a converter transformer, a converter transformer tap, an ac bus and an ac filter, the device comprising:

the limit value optimization module is used for adjusting the initial upper limit value and the initial lower limit value of the reactive exchange limit value according to the reactive exchange actual value, and correspondingly obtaining a target upper limit value and a target lower limit value; the adjusting the initial upper limit value and the initial lower limit value of the reactive exchange limit value according to the reactive exchange actual value, correspondingly obtaining the target upper limit value and the target lower limit value of the reactive exchange limit value, includes:

9. A computer device comprising a memory and a processor, the memory storing a computer program, characterized in that the processor implements the steps of the method of any of claims 1 to 7 when the computer program is executed.

10. A computer readable storage medium, on which a computer program is stored, characterized in that the computer program, when being executed by a processor, implements the steps of the method of any of claims 1 to 7.