CN105305450A - Power grid AC/DC cooperation control method after direct current block fault - Google Patents

Abstract

The invention provides a power grid AC/DC cooperation control method after a direct current block fault. The method comprises steps that characteristic quantity of a power grid is extracted based on power grid operating data obtained by a (Wide Area Measurement System), and the power limit of an interconnection tie of the regional power grid during static and stable operating is calculated; the overshoot of the power fluctuation peak value of the interconnection tie is calculated according to disturbance information which happens to the regional power grid; a load shedding quantification control measure needing to be taken is calculated based on the interconnection tie power peak value fluctuating theory and the unbalanced power redistribution theory. The method provided by the invention utilizes direct current power emergency control, so that coordination and cooperation of control measures between a large capacity direct current receiving end Central China power grid ultrahigh voltage alternating current system and a direct current system, thereby replacing or reducing the load shedding quantity of the Central China power grid, effectively improving the safety and operation efficiency of the power grid, and alleviating pressure that the imbalance impact power of the power grid is wide in influence range, the load shedding quantity is large and the like.

Description

Electrical network alternating current-direct current control method for coordinating after a kind of direct current locking fault

Technical field

The present invention relates to power grid control technical field, be specifically related to the electrical network alternating current-direct current control method for coordinating after a kind of direct current locking fault.

Background technology

Hami-Zhengzhou 800kV DC transmission engineering (being called for short " high-capacity direct current ") is that boundary electricity sends Article 1 extra-high voltage direct-current transmission engineering outside, Ye Shi China first wind fire bundling, direct current transmission project.Along with putting into operation of high-capacity direct current engineering, safe and stable operation direct current sending end northwest Xinjiang 750kV being exchanged to interconnected network and direct current receiving end North China-Central China extra-high-voltage alternating current interconnected network is had higher requirement.

As high-capacity direct current receiving end AC network, North China-Central China Power Grid will present Large Copacity alternating current-direct current at the networking initial stage and mix/parallel running, the feature that tetanic weak friendship problem shows especially.The quiet steady level of ultra high voltage demonstration project extension project circuit is 6700MW, and this quiet steady level is about 5% of single area net capacity, belongs to the weak category of regional power grid (less than 10%).Along with putting into operation of Large Copacity extra-high voltage direct-current engineering, direct current locking fault causes trend to shift on a large scale, because the quiet steady nargin of the weak tie line between regional power grid is low, is easy to cause its quiet steady destruction.When after high-capacity direct current locking, its power will all by Changzhi-Nanyang extra high voltage line, pass through Shanxi, Hebei and Shandong Power.If the associated sections stability margin of process not enough, then can there is merit angle unstability or quiet steady destruction.Because the normal operate power of high-capacity direct current is about 8000MW, direct current transmission power is large, much larger than the quiet power stabilize nargin of extra-high-voltage alternating current interconnection, tetanic weak friendship outstanding problem, need take many peace control means can ensure the safe and stable operation of interconnected network [2-3].Therefore, in the urgent need to the AC system that adapts to power network development demand and the technology of pacifying control means between direct current system and matching.

More existing documents have studied alternating current-direct current cooperation control from different perspectives at present, and document [4-5] utilizes HVDC supplementary control and power modulation controller to improve system dynamic stability respectively; Document [6] establishes the urgent branch controller of direct current power to share fault direct current power; Document [7] adopts Robust coordinated control design direct current secondary power controller; Document [8-9] improves system power-angle stability by increasing direct current power, reduces and cuts machine measure amount.

But, from existing document, for the peace control means taked after Large Copacity extra-high voltage direct-current engineering generation direct current locking fault and alternating current-direct current coordination control strategy still some deficiency.In addition, existing alternating current-direct current control method for coordinating depends on simulation calculation mostly, there is certain phantom error, cannot realize the online formulation pacifying control means.In recent years, along with the WAMS (wideareameasurementsystem based on phasor measuring set, WAMS) be gradually improved, Real-time Obtaining the whole network dynamic response data become possibility, for power system safety and stability research provides new tool.For this reason, be necessary that proposing a kind of alternating current-direct current based on response coordinates to quantize control theory computational methods.

List of references:

[1] Xu Shiyun, Wu Ping, appoints the Zhengzhou .800 kilovolt Hami extra-high voltage direct-current transmission engineering peace control strategy study [R] such as David. Beijing: China Electric Power Research Institute, 2012.

[2] Zhao Wanjun. high voltage direct current transmission project technology [M]. Beijing: China Electric Power Publishing House, 2004:55-57.

[3]KundurP.Powersystemstabilityandcontrol[M].NewYork：McGraw-HillInc，1994：228-229.

[4] Li Xingyuan, Shao Zhenxia, Tang Guangfu. decentralized coordinated control research [J] of Multi-infeed HVDC system. Proceedings of the CSEE, 2005,25 (16): 8-12.

[5] Jing Yong, Hong Chao, Yang Jinbai, etc. HVDC Modulation suppresses the research [J] of south electric network Inter-area power oscillation. electric power network technique, 2009,29 (20): 53-56.

[6] Yu Tao, Shen Shande, Ren Zhen. the research [J] that the urgent power transfer of Central China-many times, East China HVDC controls. electric power network technique, 2004,28 (12): 1-5.

[7]ToKWV，DavidAK，HammadAE.ArobustcoordinatedcontrolschemeforHVDCtransmissionwithparallelACsystems[J].IEEETransactiononPowerDelivery，1994，9(3)：1710-1716.

[8] Qi Xu, Zeng Dewen, history main forces, etc. Impacts of UHVDC Transmission on Power System Stability research [J]. electric power network technique, 2006,30 (2): 1-6.

[9] Chen Hanxiong, Hu Jingsong. the cooperation control [J] of Jinsha jiang River first phase sending end extra-high voltage DC transmission system. electric power network technique, 2008,32 (8): 10-14.

[10] Lu Cencen Wang Xiao eats. the impact [J] of direct current active power modulation on Sichuan Electric Power Network transient stability. and electric power network technique, 2012,36 (11): 140-146.

[11] yellow shake, Zheng Chao, Pang Xiaoyan, etc. Sichuan many times ± 800kV direct current delivery system direct current active power cooperation control [J]. electric power network technique, 2011,35 (5): 52-58.

[12] Wang Jianming, Sun Huadong, Zhang Jian, etc. the stability characteristic (quality) of electrical network and coordination control strategy [J] after silk screen one southern Jiangsu extra-high voltage direct-current puts into operation. electric power network technique, 2012,36 (12): 66-70.

Summary of the invention

In view of this, electrical network alternating current-direct current control method for coordinating after a kind of direct current locking fault provided by the invention, the method achieve the cooperation of control measure between high-capacity direct current receiving end regional power grid extra-high-voltage alternating current system and direct current system, alternative or reduce another regional power grid cutting load amount, effective lifting power grid security and operational efficiency, alleviation unbalanced power supply percussion power coverage is wide, the large equal pressure of cutting load amount.

The object of the invention is to be achieved through the following technical solutions:

A method for electrical network alternating current-direct current cooperation control after direct current locking fault, described electrical network is that high-capacity direct current receiving end AC network is across interconnection of large-scale power grids and described electrical network comprises two large regions electrical networks of weak electrical connection; Described regional power grid at least comprises two subsystems, and it connects subsystem closely for internal electric;

Described method comprises the steps:

The linearly connected figure of interconnection tie power fluctuation between described regional power grid is equivalent to second-order linear system model by step 1.;

Step 2. presses inertia distribution principle, calculates comprehensive stability control measure amount, exchanges security control effect total amount and minimum cutting load amount;

Step 3. determines electrical network alternating current-direct current Coordinated Control Scheme.

Preferably, described step 1 comprises:

1-1. according to the electric connecting relation of the weak Electric connection characteristic between regional power grid and described subsystem internal, two described regional power grids are reduced to a regional power grid with between another regional power grid with the linearly connected figure that dominant eigenvalues is connected;

Described linearly connected figure is equivalent to second-order linear system model by 1-2., and the frequency of oscillation of described second-order linear system model is identical with damping ratio with the frequency of oscillation of the area oscillation pattern of interconnected systems with damping ratio.

Preferably, the described second-order linear system model in described 1-2 comprises:

If a. power disturbance occurs in one of them subsystem, then described second-order linear system model is shown below:

${\mathrm{\ΔP}}_{tie}\left(t_p\right)=\mathrm{\Δ}P\frac{H_{\Σ2}}{H_{\Σ1}+H_{\Σ2}}(e^{-\mathrm{\π}\mathrm{\ξ}/\sqrt{1-{\mathrm{\ξ}}^2}}+1)---\left(1\right)$

In formula (1): Δ P _tie(t _p) be the power fluctuation of the described interconnection after power disturbance; Total inertia constant that H Σ 1 and H Σ 2 are respectively two subsystems is than the molecule of H Σ 1/H Σ 2 and denominator; ξ is the damping ratio of interconnected systems area oscillation pattern; t _pfor the time to fluctuation peak value occurs in disturbance;

If b. power disturbance occurs in another subsystem, then described second-order linear system model is shown below:

${\mathrm{\ΔP}}_{tie}\left(t_p\right)=\mathrm{\Δ}P\frac{H_{\Σ1}}{H_{\Σ1}+H_{\Σ2}}(e^{-\mathrm{\π}\mathrm{\ξ}/\sqrt{1-{\mathrm{\ξ}}^2}}+1)---\left(2\right).$

Preferably, described step 2 comprises:

2-1., in conjunction with the invariant feature of described high-capacity direct current receiving end AC network across interconnection of large-scale power grids, based on inertia distribution principle, calculates comprehensive stability control measure amount;

2-2. can modulation voltage according to the direct current of sending outside of described regional power grid, calculates described unit shut algorithm stability contorting measure effect total amount;

2-3. determines described minimum cutting load amount.

Preferably, described 2-1 comprises:

By following formula comprehensive stability control measure amount P _z:

$P_Z=P_{CN}+\frac{H_{\ΣHB}}{H_{\ΣHZ}+H_{\ΣHB}}\·P_{DC}-P_{CN\max }+{\mathrm{\ΔP}}_{CN}\left(t_p\right)---\left(3\right)$

In formula (3): P _cNfor long southern line exchanges the normal operate power of section; H _{Σ HB}, H _{Σ HZ}be respectively total inertia of two large regions electrical networks; P _dCfor high-capacity direct current locking power; P _cNmaxfor long southern line steady state stability limit; Δ P _cN(t _p) be long southern linear heat generation rate fluctuation peak value overshoot.

Preferably, described 2-2 comprises:

Be calculated as follows described unit shut algorithm stability contorting measure effect total amount P _{z (AC)}:

$P_{Z\left(AC\right)}=P_Z-\frac{H_{\ΣHB}}{H_{\ΣHZ}+H_{\ΣHB}}\·\underset{i=1}{\overset{n}{\Σ}}{P}_{i\left(\mathrm{mod}\right)}---\left(4\right)$

In formula (4): P _{i (mod)}be that i-th direct current that a regional power grid is sent to another regional power grid can modulate quantity of power; for direct current can modulate the summation of quantity of power.

Preferably, described 2-3 comprises:

C., under not considering that urgent prompt drop regional power grid gives another regional power grid direct current power situation, described minimum cutting load amount C is calculated as follows _l1:

$C_{L1}=\frac{H_{\mathrm{\Σ}HZ}+H_{\mathrm{\Σ}HB}}{H_{\mathrm{\Σ}HZ}}{P}_Z---\left(5\right)$

D., under considering that urgent prompt drop regional power grid gives another regional power grid direct current power situation, described minimum cutting load amount C is calculated as follows _l2for:

$C_{L2}=\frac{H_{\mathrm{\Σ}HZ}+H_{\mathrm{\Σ}HB}}{H_{\mathrm{\Σ}HZ}}{P}_{Z\left(AC\right)}---\left(6\right).$

Preferably, described step 3 comprises:

According to described dominant eigenvalues head pendulum peak value theoretical and imbalance power reallocation is theoretical and after electric network fault or disturbance imbalance power at partition characteristic, formulate direct current receiving end electrical network alternating current-direct current online, in real time and coordinate science digital method, determine electrical network alternating current-direct current Coordinated Control Scheme.

As can be seen from above-mentioned technical scheme, the invention provides the electrical network alternating current-direct current control method for coordinating after a kind of direct current locking fault, the operation of power networks data that the method obtains based on WAMS, extract electrical network characteristic quantity, zoning interconnecting ties steady stability operational limit power; According to the disturbance information that regional power grid occurs, calculate interconnection tie power fluctuation peak overshoot; The cutting load quantified controlling measure taked is needed based on dominant eigenvalues head pendulum peak value theory and imbalance power reallocation theory calculate.The method that the present invention proposes utilizes direct current power emergency control, realize the cooperation of control measure between high-capacity direct current receiving end Central China Power Grid extra-high-voltage alternating current system and direct current system, alternative or reduce Central China Power Grid cutting load amount, effective lifting power grid security and operational efficiency, alleviation unbalanced power supply percussion power coverage is wide, the large equal pressure of cutting load amount.

With immediate prior art ratio, technical scheme provided by the invention has following excellent effect:

1, in technical scheme provided by the present invention, based on the real-time response characteristic quantity of operation of power networks, zoning interconnecting ties steady stability operational limit power; According to the disturbance information that regional power grid occurs, calculate interconnection tie power fluctuation peak overshoot; The safety and stability quantified controlling measure taked is needed based on dominant eigenvalues head pendulum peak value theory and imbalance power reallocation theory calculate.In the method proposed, calculated data all obtains by WAMS, have nothing to do with electric network model parameter, system conditions, not only can be Power System Off-line simulation calculation and Technical Reference is provided, also can be used for online formulation and the operation of the measure of alternating current-direct current cooperation control, have broad application prospects.

2, technical scheme provided by the present invention, utilize direct current power emergency control, realize the cooperation of control measure between high-capacity direct current receiving end Central China Power Grid extra-high-voltage alternating current system and direct current system, alternative or reduce Central China Power Grid cutting load amount, effective lifting power grid security and operational efficiency, alleviation unbalanced power supply percussion power coverage is wide, the large equal pressure of cutting load amount.

3, technical scheme provided by the invention, is widely used, and has significant Social benefit and economic benefit.

Accompanying drawing explanation

Fig. 1 is the flow chart of the electrical network alternating current-direct current control method for coordinating after a kind of direct current locking fault of the present invention;

Fig. 2 is the schematic flow sheet of step 1 in acquisition methods of the present invention;

Fig. 3 is the schematic flow sheet of step 2 in acquisition methods of the present invention;

Fig. 4 is high-capacity direct current access electric network composition schematic diagram in embody rule example of the present invention;

Fig. 5 is the rack schematic diagram of North China-Central China Power Grid in embody rule example of the present invention;

Fig. 6 is the valve systems such as two machines of two regional internet electrical networks in embody rule example of the present invention;

Fig. 7 is the frequency response curve under the power shortage of Central China Power Grid 5000MW in embody rule example of the present invention;

Fig. 8 is the frequency response curve under the power shortage of Central China Power Grid 6000MW in embody rule example of the present invention.

Embodiment

Below in conjunction with the accompanying drawing in the embodiment of the present invention, be clearly and completely described the technical scheme in the embodiment of the present invention, obviously, described embodiment is only the present invention's part embodiment, instead of whole embodiments.Based on embodiments of the invention, those of ordinary skill in the art, not making the every other embodiment obtained under creative work prerequisite, belong to the scope of protection of the invention.

As shown in Figure 1, the invention provides the method for the electrical network alternating current-direct current cooperation control after a kind of direct current locking fault, described electrical network is that high-capacity direct current receiving end AC network is across interconnection of large-scale power grids and described electrical network comprises two large regions electrical networks of weak electrical connection; Described regional power grid at least comprises two subsystems, and it connects subsystem closely for internal electric;

Comprise the steps:

The linearly connected figure of interconnection tie power fluctuation between regional power grid is equivalent to second-order linear system model by step 1.;

Step 2. presses inertia distribution principle, calculates comprehensive stability control measure amount, exchanges security control effect total amount and minimum cutting load amount;

Step 3. determines electrical network alternating current-direct current Coordinated Control Scheme.

As shown in Figure 2, step 1 comprises:

1-1. according to the electric connecting relation of the weak Electric connection characteristic between regional power grid and subsystem internal, two regional power grids are reduced to a regional power grid with between another regional power grid with the linearly connected figure that dominant eigenvalues is connected;

Linearly connected figure is equivalent to second-order linear system model by 1-2., and the frequency of oscillation of second-order linear system model is identical with damping ratio with the frequency of oscillation of the area oscillation pattern of interconnected systems with damping ratio.

Wherein, the second-order linear system model in 1-2 comprises:

If a. power disturbance occurs in subsystem 1, then second-order linear system model is:

${\mathrm{\ΔP}}_{tie}\left(t_p\right)=\mathrm{\Δ}P\frac{H_{\Σ2}}{H_{\Σ1}+H_{\Σ2}}(e^{-\mathrm{\π}\mathrm{\ξ}/\sqrt{1-{\mathrm{\ξ}}^2}}+1)---\left(1\right)$

In formula (1): Δ P _tie(t _p) be the power fluctuation of the interconnection after power disturbance; It is the molecule in H Σ 1/H Σ 2 and denominator that H Σ 1 and H Σ 2 are respectively subsystem 1 with total inertia constant ratio of subsystem 2; ξ is the damping ratio of interconnected systems area oscillation pattern; t _pfor the time to fluctuation peak value occurs in disturbance;

If b. power disturbance occurs in subsystem 2, then second-order linear system model is:

${\mathrm{\ΔP}}_{tie}\left(t_p\right)=\mathrm{\Δ}P\frac{H_{\Σ1}}{H_{\Σ1}+H_{\Σ2}}(e^{-\mathrm{\π}\mathrm{\ξ}/\sqrt{1-{\mathrm{\ξ}}^2}}+1)---\left(2\right).$

As shown in Figure 3, step 2 comprises:

2-1., in conjunction with the invariant feature of high-capacity direct current receiving end AC network across interconnection of large-scale power grids, based on inertia distribution principle, calculates comprehensive stability control measure amount;

2-2. can modulation voltage according to the direct current of sending outside of regional power grid, calculates unit shut algorithm stability contorting measure effect total amount;

2-3. calculates minimum cutting load amount.

Wherein, 2-1 comprises:

In conjunction with the invariant feature of high-capacity direct current receiving end AC network across interconnection of large-scale power grids, based on inertia distribution principle, calculate comprehensive stability control measure amount P _z:

$P_Z=P_{CN}+\frac{H_{\ΣHB}}{H_{\ΣHZ}+H_{\ΣHB}}\·P_{DC}-P_{CN\max }+{\mathrm{\ΔP}}_{CN}\left(t_p\right)---\left(3\right)$

In formula (3): P _cNfor long southern line exchanges the normal operate power of section; H _{Σ HB}, H _{Σ HZ}be respectively total inertia of two large regions electrical networks; P _dCfor high-capacity direct current locking power; P _cNmaxfor long southern line steady state stability limit; Δ P _cN(t _p) be long southern linear heat generation rate fluctuation peak value overshoot.

Wherein, 2-2 comprises:

Direct current of sending outside according to regional power grid can modulation voltage, calculates unit shut algorithm stability contorting measure effect total amount P _{z (AC)}:

$P_{Z\left(AC\right)}=P_Z-\frac{H_{\ΣHB}}{H_{\ΣHZ}+H_{\ΣHB}}\·\underset{i=1}{\overset{n}{\Σ}}{P}_{i\left(\mathrm{mod}\right)}---\left(4\right)$

In formula (4): P _{i (mod)}be that i-th direct current that a regional power grid is sent to another regional power grid can modulate quantity of power; for direct current can modulate the summation of quantity of power.

Wherein, 2-3 comprises:

C. under not considering that urgent prompt drop regional power grid gives another regional power grid direct current power situation, minimum cutting load amount C _l1for:

$C_{L1}=\frac{H_{\mathrm{\Σ}HZ}+H_{\mathrm{\Σ}HB}}{H_{\mathrm{\Σ}HZ}}{P}_Z---\left(5\right)$

D. under consideration urgent prompt drop regional power grid gives another regional power grid direct current power situation, minimum cutting load amount C _l2for:

$C_{L2}=\frac{H_{\mathrm{\Σ}HZ}+H_{\mathrm{\Σ}HB}}{H_{\mathrm{\Σ}HZ}}{P}_{Z\left(AC\right)}---\left(6\right).$

Wherein, step 3 comprises:

According to dominant eigenvalues head pendulum peak value theoretical and imbalance power reallocation is theoretical and after electric network fault or disturbance imbalance power at partition characteristic, formulate direct current receiving end electrical network alternating current-direct current online, in real time and coordinate science digital method, obtain electrical network alternating current-direct current Coordinated Control Scheme.

The present invention, for North China-Central China two large regional grid, provides the embody rule example of the electrical network alternating current-direct current control method for coordinating after a kind of direct current locking fault, as follows:

The invention provides a kind of in conjunction with the major stable feature of high-capacity direct current receiving end AC network across interconnection of large-scale power grids, based on inertia distribution principle, the computational methods of comprehensive steady control means amount and alternating current-direct current cooperation control amount (comprising HVDC Modulation and receiving end electrical network cutting load measure amount) after quantum chemical method direct current locking fault.Method comprises the following steps:

The inearized model of interconnection tie power fluctuation between high-capacity direct current receiving end North China-Central China Power Grid is expressed as a second-order linear system;

Based on the real-time response characteristic quantity of operation of power networks, zoning interconnecting ties steady stability operational limit power;

According to the disturbance information that regional power grid occurs, calculate interconnection tie power fluctuation peak overshoot;

Based on dominant eigenvalues head pendulum peak value, theoretical and imbalance power reallocation theory, calculates the safety and stability quantified controlling measure needing to take.

After quantum chemical method direct current locking fault, comprehensive steady control means amount and alternating current-direct current cooperation control amount (comprising HVDC Modulation and receiving end electrical network cutting load measure amount) computational methods, be first expressed as a second-order linear system by the inearized model of interconnection tie power fluctuation between high-capacity direct current receiving end North China-Central China Power Grid.

One, DC engineering and receiving end electrical network overview:

Hami-Zhengzhou DC transmission engineering is from Hami Prefecture of Xinjiang Uygur Autonomous Regions Hami current conversion station, and to the east of Zhengzhou, Zhengzhou City Henan Province current conversion station, transmission distance is about 2110km.The specified transmission line capability 8000MW of this project, realized bipolar low side in 2013 and puts into operation, and 2014 bipolar puts into operation.Hami current conversion station of Northwest Grid is generally converting plant and runs, and the Zhengzhou current conversion station of Central China Power Grid is generally Inverter Station and runs.The schematic diagram of high-capacity direct current access electrical network in 2014 as shown in Figure 4.

As can be seen from Figure 4, high-capacity direct current rectification side Hami current conversion station becomes access Xinjiang, northwest 750kV networking passage through 750/500kV contact.In receiving end Central China Power Grid, inverter side Zhengzhou current conversion station accesses Central China major network by 6 times 500kV circuits, and Zhengzhou current conversion station change of current bus rating operating voltage is 525kV.

Receiving end AC network will realize North China-Central China ultra high voltage the end of the year 2013 and synchronously networks, East China Power Grid independent operating, and Shanghai, Huaihe River extra-high voltage project is built up; The end of the year 2014 still synchronously networked based on North China-Central China.North China-Central China extra-high-voltage alternating current grid structure schematic diagram as shown in Figure 5.

Two, security and stability control measurement coordinates Quantitative Calculation Method:

1. the power fluctuation of liang regional internet system alternating current interconnection calculates:

For two large regional grids of weak electrical link, because subsystem internal electrical link is tight, two machine system reduced representations shown in available Fig. 6, P in Fig. 6 _tiefor dominant eigenvalues.

The theoretical analysis is derived, and the inearized model of Liang great district electric power system interconnection tie power fluctuation can be expressed as a second-order linear system, and its frequency of oscillation is consistent with the area oscillation pattern of interconnected systems with damping ratio.Suppose that subsystem 1 is H with total inertia constant ratio of subsystem 2 _{Σ 1}/ H _{Σ 2}.If power disturbance occurs in subsystem 1, the power fluctuation Δ P of interconnection after power disturbance _tie(t _p) computing formula is

${\mathrm{\ΔP}}_{tie}\left(t_p\right)=\mathrm{\Δ}P\frac{H_{\Σ2}}{H_{\Σ1}+H_{\Σ2}}(e^{-\mathrm{\π}\mathrm{\ξ}/\sqrt{1-{\mathrm{\ξ}}^2}}+1)---\left(1\right)$

In formula: ξ is the damping ratio of interconnected systems area oscillation pattern; t _pfor the time to fluctuation peak value occurs in disturbance.If power disturbance occurs in subsystem 2, then by the molecule H of formula (1) _{Σ 2}change H into _{Σ 1}.

As can be seen from above-mentioned computing formula, determine that the most critical factor of interconnection tie power fluctuation is total inertia constant ratio of regional power grid and the damping ratio of interconnected systems area oscillation pattern, the moment reaching peak value is determined by frequency of oscillation.Larger, that power disturbance side regional power grid the occurs total inertia constant of damping ratio is larger, and interconnection tie power fluctuation peak is less.

2. receiving end AC network imbalance power controlled quentity controlled variable calculates:

(1) the reallocation elasticity theory of imbalance power:

As high-capacity direct current receiving end AC network, North China-Central China Power Grid will present Large Copacity alternating current-direct current at the networking initial stage and mix/parallel running, the feature that tetanic weak friendship problem shows especially.The quiet steady level of ultra high voltage demonstration project extension project circuit is 6700MW, and this quiet steady level is about 5% of single area net capacity, belongs to the weak category of regional power grid (less than 10%).Along with putting into operation of Large Copacity extra-high voltage direct-current engineering, direct current locking fault causes trend to shift on a large scale, because the quiet steady nargin of the weak tie line between regional power grid is low, is easy to cause its quiet steady destruction.When after high-capacity direct current locking, its power will all by Changzhi-Nanyang extra high voltage line, pass through Shanxi, Hebei and Shandong Power.If the associated sections stability margin of process not enough, then can there is merit angle unstability or quiet steady destruction.Because the normal operate power of high-capacity direct current is about 8000MW,

Direct current transmission power is large, and much larger than the quiet power stabilize nargin of extra-high-voltage alternating current interconnection, tetanic weak friendship outstanding problem, need take a large amount of peace control means can ensure the safe and stable operation of interconnected network.Therefore, adapt to pacify control means compounding technique between the AC system of power network development demand and direct current system in the urgent need to research.

(2) comprehensive steady control means amount quantum chemical method:

In conjunction with the major stable feature of high-capacity direct current receiving end AC network across interconnection of large-scale power grids, based on inertia distribution principle, the computational methods of the comprehensive steady control means amount of quantum chemical method and alternating current-direct current cooperation control amount (comprising HVDC Modulation and receiving end electrical network cutting load measure amount) are proposed.

1) ask for and meet multiobject comprehensive stability control measure amount.

Power flow transfer after causing accident quiet steady destruction be across the topmost its instability forms of large regional grid, for maintaining the stability of synchronization of important section two ends electrical network, the comprehensive steady control means amount PZ that need take obtains by following formula:

$P_Z=P_{CN}+\frac{H_{\ΣHB}}{H_{\ΣHZ}+H_{\ΣHB}}\·P_{DC}-P_{CN\max }+{\mathrm{\ΔP}}_{CN}\left(t_p\right)---\left(3\right)$

In formula: P _cNfor long southern line exchanges the normal operate power of section; H _{Σ HB}, H _{Σ HZ}be respectively total inertia of North China, Central China regional power grid; P _dCfor high-capacity direct current locking power; P _cNmaxfor long southern line steady state stability limit; Δ P _cN(t _p) be long southern linear heat generation rate fluctuation peak value overshoot, try to achieve by formula (1).

2) interchange peace control (unit shut algorithm) effect total amount is asked for.

Sending direct current outside according to Central China Power Grid can modulation voltage, can calculate the unit shut algorithm stability contorting measure effect total amount P needing to take _{z (AC)}:

$P_{Z\left(AC\right)}=P_Z-\frac{H_{\ΣHB}}{H_{\ΣHZ}+H_{\ΣHB}}\·\underset{i=1}{\overset{n}{\Σ}}{P}_{i\left(\mathrm{mod}\right)}---\left(3\right)$

In formula: P _{i (mod)}for Central China send East China Power Grid i-th direct current to modulate quantity of power; for direct current can modulate quantity of power sum.

3) the minimum cutting load amount that need take is asked for.

Under not considering that East China direct current power situation is sent in urgent prompt drop Central China, ensure that long southern line safe and stable operation need excise Central China Power Grid load and be

$C_{L1}=\frac{H_{\mathrm{\Σ}HZ}+H_{\mathrm{\Σ}HB}}{H_{\mathrm{\Σ}HZ}}{P}_Z---\left(4\right)$

Under considering that East China direct current power situation is sent in urgent prompt drop Central China, the cutting load amount that need take is

$C_{L2}=\frac{H_{\mathrm{\Σ}HZ}+H_{\mathrm{\Σ}HB}}{H_{\mathrm{\Σ}HZ}}{P}_{Z\left(AC\right)}---\left(5\right)$

After electric power system emergent power imbalance, " distribute " power that causes by inertia and shift that to stablize the pressure of formation to extra-high-voltage alternating current section maximum on a large scale, the cutting load amount needing to take at receiving end electrical network can be calculated according to formula (4)-(5).In above-mentioned computational methods, calculated data all obtains by the real-time response of WAMS, can realize in line computation.

Three, high-capacity direct current locking fault alternating current-direct current coordinates science digital method simulating, verifying:

1. direct current locking fault peace control means theory calculate:

Mode is sent for North China-Central China ultra high voltage passage (ultra high voltage demonstration extension project) north, high-capacity direct current generation locking fault can not constitute a threat to the safety and stability of electrical network, but under mode is sent in south, single bipolar locking fault all likely causes North China-Central China Power Grid to lose synchronism stability and off-the-line.This section, in North China-withered phase mode of Central China ultra high voltage networking in 2013, is coordinated science digital method according to North China-Central China Power Grid alternating current-direct current and is formulated flow process, and in conjunction with North China-Central China networking data, check the peace control means quantization formula provided above.

1) long southern linear heat generation rate fluctuation peak value overshoot is calculated.

Try to achieve long southern linear heat generation rate fluctuation peak value overshoot according to formula (1) and be about 1000MW.

2) the comprehensive control measures amount keeping long southern line stabilization is calculated.

Under which, long Nan Xiannan send operate power to be 5000MW, and its steady state stability limit is about 6500MW, and after high-capacity direct current bipolar locking, Central China Power Grid will occur the power shortage of 8000MW.In North China-Central China networking stage, North China, the total ratio of inertias in Central China are about 1.3:1, and according to imbalance power reallocation characteristic, Central China Power Grid power shortage amount will just be added on long southern line by a certain percentage.The comprehensive control measures amount of the long southern line stabilization of maintenance is

$P_Z=P_{CN}+\frac{H_{\mathrm{\Σ}HB}}{H_{\mathrm{\Σ}HZ}+H_{\mathrm{\Σ}HB}}{P}_{DC}-P_{CN\max }+{\mathrm{\ΔP}}_{CN}\left(t_p\right)=(5000+\frac{1.3}{1.3+1}\×8000-6500+1000)MW=4022MW$

3) calculate consideration and under not considering that direct-current emergency controls 2 kinds of situations, ensure that the interchange peace of long southern line safe and stable operation controls effect amount.

If do not consider, East China direct current power is sent in urgent prompt drop Central China, namely then ensure the interchange peace control effect amount of long southern line safe and stable operation

$P_{Z\left(AC\right)}=P_Z-\frac{H_{\ΣHB}}{H_{\ΣHZ}+H_{\ΣHB}}\·\underset{i=1}{\overset{n}{\Σ}}{P}_{i\left(\mathrm{mod}\right)}=4022MW$

If consider, East China direct current power 4400MW is sent in urgent prompt drop Central China, then ensure that the interchange peace control effect amount of long southern line safe and stable operation is

$P_{Z\left(AC\right)}=P_Z-\frac{H_{\ΣHB}}{H_{\ΣHZ}+H_{\ΣHB}}\·\underset{i=1}{\overset{n}{\Σ}}{P}_{i\left(\mathrm{mod}\right)}=(4022-\frac{1.3}{1.3+1}\×4400)MW=1536MW$

4) calculate consideration and under not considering that direct-current emergency controls 2 kinds of situations, ensure the cutting load amount of long southern line safe and stable operation.

If do not consider, East China direct current power is sent in urgent prompt drop Central China, then ensure that long southern line safe and stable operation need excise Central China Power Grid load:

$C_{L1}=\frac{H_{\mathrm{\Σ}HZ}+H_{\mathrm{\Σ}HB}}{H_{\mathrm{\Σ}HZ}}{P}_Z=\frac{1.3+1}{1.3}\·4022MW=7116MW$

If consider, East China direct current power 4400MW is sent in urgent prompt drop Central China,

Then ensure that long southern line safe and stable operation need excise Central China Power Grid load:

$C_{L2}=\frac{H_{\mathrm{\Σ}HZ}+H_{\mathrm{\Σ}HB}}{H_{\mathrm{\Σ}HZ}}{P}_{Z\left(AC\right)}=\frac{1.3+1}{1.3}\·1536MW=2718MW$

5) the peace control means amount ensureing long southern line safe and stable operation is chosen.

According to result of calculation above, after high-capacity direct current bipolar locking, when not considering direct current power emergency control, ensure that the cutting load amount of long southern line safe and stable operation is 7116MW; Under considering direct current power emergency control 4400MW situation, ensure that the cutting load amount of long southern line safe and stable operation is 2718MW.

2. direct current locking fault peace control means simulation analysis:

This section carries out simulating, verifying to proposed science digital method result of calculation.According to statistics, North China in 2013-long Nan Xiannan of Central China ultra high voltage withered phase ultra high voltage of networking send North China under power 5000MW mode, Central China Power Grid load condition as shown in table 1.

Table 1

First the frequency response situation of Central China Power Grid after the southern line off-the-line of analysis length.Simulation result shows, when after long southern line off-the-line, Central China Power Grid will occur the power shortage of 5000MW, account for 3.16% of Central China Power Grid total load level, Central China Power Grid frequency decrease will be caused to be about 0.4Hz, as shown in Figure 7.

When Central China Power Grid gross power vacancy reaches 6000MW (accounting for Central China Power Grid total load 3.8%), as shown in Figure 8, Central China Power Grid frequency decreases beyond 0.75Hz, reaches the operating value 49.25Hz of Central China Power Grid three lines of defence low-frequency load reduction, will cause Central China Power Grid large losses load.

Under aforesaid way, if after there is DC bipolar block fault in high-capacity direct current Operation at full power situation, do not take the measure of excision load, to the power shortage of 8000MW be there is in Central China Power Grid, imbalance power transfer can cause the long southern line off-the-line of ultra high voltage, cause Central China Power Grid power shortage to reach 13000MW, account for Central China Power Grid total load more than 8%, the action of Central China Power Grid low-frequency load reduction will be caused.Now, Central China Power Grid is except the power shortage caused after needing to compensate high-capacity direct current locking, and also need to compensate the power shortage caused after long southern line disconnects, the cutting load amount that low-frequency load reduction action causes increases.Therefore, when ultra high voltage interconnection south, Central China, North China is sent, peace control means during high-capacity direct current locking fault, must be taked to ensure extra-high-voltage alternating current electrical network not off-the-line.

The peace control means taked required for being obtained under North China in 2013-withered large mode of Central China networking after high-capacity direct current single, double pole locking fault by simulation calculation is as shown in table 2.

Table 2

The result of calculation of table 2 shows, is not considering that East China direct current power is sent in urgent prompt drop Central China, ensures that long southern line safe and stable operation need excise Central China Power Grid load 6500MW simultaneously; Under East China direct current power 4400MW situation is sent in consideration emergency lifting Central China, Central China Power Grid load 2300MW need be excised.According to the result of 3.1 joint peace control means quantum chemical method theoretical methods, when not considering direct current power emergency control, ensure that the cutting load amount of long southern line safe and stable operation is 7116MW; When considering direct current power emergency control 4400MW, the peace control means amount obtained can ensure the safe and stable operation of Central China Power Grid after direct current locking fault, and has certain nargin, and its validity obtains abundant checking.

Four, alternating current-direct current is coordinated science digital method and is formulated flow process:

The important service data of high-capacity direct current receiving end AC network is extracted based on electrical network wide area multiple information sources, according to imbalance power after interconnection power system system dominant eigenvalues head pendulum peak value theoretical calculation method, electric network fault or disturbance at partition characteristic, direct current receiving end electrical network alternating current-direct current can be formulated online, in real time and coordinate science digital method, be roughly divided into following step:

1) according to the electrical network actual operating data that WAMS obtains, control oscillation modes between computational analysis large regional grid, and North China, the total inertia time constant ratio of Central China Power Grid.The disturbance occurred according to electrical network or fault message, the power shortage that judging area electrical network occurs or surplus situation, calculate North China-region, Central China by formula (1) and get in touch with line length south linear heat generation rate fluctuation peak value overshoot.

2) according to North China-Central China Power Grid actual operating data, the long southern line operate power of monitoring, the long southern line stabilization of computational analysis run nargin, the power shortage that the disturbance occurred by electrical network or fault message judging area electrical network occur or surplus situation, and integrating step 1) the interconnection tie power fluctuation peak overshoot that obtains, obtain maintaining by formula (2) the comprehensive stability control measure amount that long southern line safe and stable operation needs to take.

3) can emergency control amount according to North China-Central China Power Grid parallel connection direct, and step 2) the comprehensive stability control measure amount that obtains, calculated by formula (3) and ensure that the interchange required for long southern line safe and stable operation pacifies control amount, i.e. cutting load control measure amount.

4) according to North China, the total inertia time constant ratio of Central China Power Grid, and step 3) the interchange peace control amount that obtains, the cutting load amount ensured required for long southern line safe and stable operation is calculated by formula (4).Follow in computational process and send receiving end to take control measure amount can not exceed locking direct current power size.

5) Integrated comparative step 4) machine of cutting that obtains or cutting load amount, choose the cutting load amount simultaneously ensureing long southern line safe and stable operation, reach the object of high-capacity direct current receiving end North China-Central China Power Grid safe and stable operation.

Above embodiment is only in order to illustrate that technical scheme of the present invention is not intended to limit; although with reference to above-described embodiment to invention has been detailed description; those of ordinary skill in the field still can modify to the specific embodiment of the present invention or equivalent replacement; and these do not depart from any amendment of spirit and scope of the invention or equivalent replacement, it is all being applied within the claims of the present invention awaited the reply.

Claims (8)

1. a method for the electrical network alternating current-direct current cooperation control after direct current locking fault, described electrical network is that high-capacity direct current receiving end AC network is across interconnection of large-scale power grids and described electrical network comprises two large regions electrical networks of weak electrical connection; Described regional power grid at least comprises two subsystems, and it connects subsystem closely for internal electric;

It is characterized in that, described method comprises the steps:

The linearly connected figure of interconnection tie power fluctuation between described regional power grid is equivalent to second-order linear system model by step 1.;

Step 2. presses inertia distribution principle, calculates comprehensive stability control measure amount, exchanges security control effect total amount and minimum cutting load amount;

Step 3. determines electrical network alternating current-direct current Coordinated Control Scheme.

2. the method for claim 1, is characterized in that, described step 1 comprises:

1-1. according to the electric connecting relation of the weak Electric connection characteristic between regional power grid and described subsystem internal, two described regional power grids are reduced to a regional power grid with between another regional power grid with the linearly connected figure that dominant eigenvalues is connected;

Described linearly connected figure is equivalent to second-order linear system model by 1-2., and the frequency of oscillation of described second-order linear system model is identical with damping ratio with the frequency of oscillation of the area oscillation pattern of interconnected systems with damping ratio.

3. method as claimed in claim 2, it is characterized in that, the described second-order linear system model in described 1-2 comprises:

If a. power disturbance occurs in one of them subsystem, then described second-order linear system model is shown below:

${\mathrm{\ΔP}}_{tie}\left(t_p\right)=\mathrm{\Δ}P\frac{H_{\mathrm{\Σ}2}}{H_{\mathrm{\Σ}1}+H_{\mathrm{\Σ}2}}(e^{-\mathrm{\π}\mathrm{\ξ}/\sqrt{1-{\mathrm{\ξ}}^2}}+1)---\left(1\right)$

In formula (1): Δ P _tie(t _p) be the power fluctuation of the described interconnection after power disturbance; Total inertia constant that H Σ 1 and H Σ 2 are respectively two subsystems is than the molecule of H Σ 1/H Σ 2 and denominator; ξ is the damping ratio of interconnected systems area oscillation pattern; t _pfor the time to fluctuation peak value occurs in disturbance;

If b. power disturbance occurs in another subsystem, then described second-order linear system model is shown below:

${\mathrm{\ΔP}}_{tie}\left(t_p\right)=\mathrm{\Δ}P\frac{H_{\mathrm{\Σ}1}}{H_{\mathrm{\Σ}1}+H_{\mathrm{\Σ}2}}(e^{-\mathrm{\π}\mathrm{\ξ}/\sqrt{1-{\mathrm{\ξ}}^2}}+1)---\left(2\right).$

4. the method for claim 1, is characterized in that, described step 2 comprises:

2-1., in conjunction with the invariant feature of described high-capacity direct current receiving end AC network across interconnection of large-scale power grids, based on inertia distribution principle, calculates comprehensive stability control measure amount;

2-2. can modulation voltage according to the direct current of sending outside of described regional power grid, calculates described unit shut algorithm stability contorting measure effect total amount;

2-3. determines described minimum cutting load amount.

5. method as claimed in claim 4, it is characterized in that, described 2-1 comprises:

By following formula comprehensive stability control measure amount P _z:

$P_Z=P_{CN}+\frac{H_{\mathrm{\Σ}HB}}{H_{\mathrm{\Σ}HZ}+H_{\mathrm{\Σ}HB}}\·P_{DC}-P_{CNmax}+{\mathrm{\ΔP}}_{CN}\left(t_p\right)---\left(3\right)$

In formula (3): P _cNfor long southern line exchanges the normal operate power of section; H _{Σ HB}, H _{Σ HZ}be respectively total inertia of two large regions electrical networks; P _dCfor high-capacity direct current locking power; P _cNmaxfor long southern line steady state stability limit; Δ P _cN(t _p) be long southern linear heat generation rate fluctuation peak value overshoot.

6. method as claimed in claim 5, it is characterized in that, described 2-2 comprises:

Be calculated as follows described unit shut algorithm stability contorting measure effect total amount P _{z (AC)}:

$P_{Z\left(AC\right)}=P_Z-\frac{H_{\mathrm{\Σ}HB}}{H_{\mathrm{\Σ}HZ}+H_{\mathrm{\Σ}HB}}\·\underset{i=1}{\overset{n}{\Σ}}{P}_{i\left(\mathrm{mod}\right)}---\left(4\right)$

In formula (4): P _{i (mod)}be that i-th direct current that a regional power grid is sent to another regional power grid can modulate quantity of power; for direct current can modulate the summation of quantity of power.

7. method as claimed in claim 5, it is characterized in that, described 2-3 comprises:

C., under not considering that urgent prompt drop regional power grid gives another regional power grid direct current power situation, described minimum cutting load amount C is calculated as follows _l1:

$C_{L1}=\frac{H_{\mathrm{\Σ}HZ}+H_{\mathrm{\Σ}HB}}{H_{\mathrm{\Σ}HZ}}{P}_Z---\left(5\right)$

D., under considering that urgent prompt drop regional power grid gives another regional power grid direct current power situation, described minimum cutting load amount C is calculated as follows _l2for:

$C_{L2}=\frac{H_{\mathrm{\Σ}HZ}+H_{\mathrm{\Σ}HB}}{H_{\mathrm{\Σ}HZ}}{P}_{Z\left(AC\right)}---\left(6\right).$

8. the method for claim 1, is characterized in that, described step 3 comprises:

According to described dominant eigenvalues head pendulum peak value theoretical and imbalance power reallocation is theoretical and after electric network fault or disturbance imbalance power at partition characteristic, formulate direct current receiving end electrical network alternating current-direct current online, in real time and coordinate science digital method, determine electrical network alternating current-direct current Coordinated Control Scheme.