CN103701140A - Dynamic reactive power reserve optimization method for improving transient voltage stability of alternating-current and direct-current power grid - Google Patents

Abstract

The invention provides a dynamic reactive power reserve optimization method for improving transient voltage stability of an alternating-current and direct-current power grid. The method comprises the steps of determining a key fault set and a key node set which influence the transient voltage stability of a power system, and sequentially ranking nodes; adjusting reactive power output of dynamic reactive power compensation equipment and calculating the trajectory sensitivity of the dynamic reactive power compensation equipment; ranking m dynamic reactive power compensation equipment and calculating the weight coefficients of the nodes in the dynamic reactive power compensation equipment; calculating the capacities of the dynamic reactive power compensation equipment, establishing a dynamic reactive power reserve optimization model and solving the dynamic reactive power reserve optimization model. The dynamic reactive power reserve optimization method for improving the transient voltage stability of the alternating-current and direct-current power grid provides auxiliary decision-making support for improving the transient voltage stability of the multi-direct-current-drop-point power grid, and has great importance in improving the allowance of the transient voltage stability of the large-scale alternating-current and direct-current power grid, establishing a smooth power transmission passage between a transmitting end and a receiving end, improving the transmission capacity of the alternating-current and direct-current power transmission passage and improving the operation economy and the power quality of the power grid.

Description

Improve the standby optimization method of dynamic reactive of alternating current-direct current electrical network Transient Voltage Stability

Technical field

The present invention relates to a kind of optimization method, specifically relate to a kind of standby optimization method of dynamic reactive that improves alternating current-direct current electrical network Transient Voltage Stability.

Background technology

Direct current transportation has at a distance, the advantage of large volume transport, and regulating and controlling is flexible, thereby is used to the interconnected of large scale electric network, becomes one of the main transmission channel of " transferring electricity from the west to the east ".Orderly propelling along with extra-high voltage grid construction, to 2015, ultra high voltage and transregional, transnational electrical network transmission capacity are 2.61 hundred million kilowatts, ultra high voltage AC and DC has been born more than 80% electric power transfer, extra-high voltage grid ability to transmit electricity improves greatly compared with ultrahigh voltage AC and DC, communication channel is born to the ability of trend transfer and has higher requirement." three China " receiving end electrical network is subject to electric ratio by AC-HVDC path partially, to be subject to electricity higher than regular meeting by accounting for 32% of regional total load, particularly East China from district.Spy/super high voltage direct current electricity transmission system is concentrated drop point " three China " receiving end electrical network, and the direct current system sum of drop point East China reaches 9 times, forms direct current group.Electrical distance between the direct current drop point of East China Power Grid, between direct current drop point and alternating current interconnection is nearer, so near the fault in ac transmission system catastrophe failure of alternating current-direct current interconnection and direct current drop point all can produce larger impact to receiving end electrical network.For the receiving end electrical network of Ac/dc Power Systems, the factors such as the grid structure of receiving end electrical network, load level, power distribution, direct current drop point, hvdc control mode all can exert an influence to the voltage stability of system.Continuous increase and load center feature increasingly significant along with electrical network scale, the Voltage-stabilizing Problems of the receiving end such as East China, Guangdong electrical network becomes increasingly conspicuous in recent years, researcher starts system voltage stable problem to bring in the consideration category of idle work optimization, but still has very large room for development on the depth & wideth of research.In addition, in electric power system, there is multiple dynamic passive compensation equipment, as generator, switched capacitors, SVC, on-load tap-changing transformer etc.A lot of research about dynamic reactive optimization at present only lays particular emphasis on a certain equipment wherein, and has ignored the cooperation between equipment.The algorithm of most Electrical Power System Dynamic idle work optimization has only been verified its correctness in mini system, also there is no practical large electrical network dynamic reactive optimized algorithm, be therefore necessary to carry out about can be applicable to the research of the dynamic reactive optimization method of large-scale electrical power system.Aspect standby, reserve is the emphasis of paying close attention to always, special also more rare for the research of Reactive Power Reserve, especially for the dynamic reactive of multi-infeed HVDC receiving end electrical network is standby, lacks especially.Reactive Power Reserve optimization and voltage stabilization belong to system realm problem, and each dynamic passive compensation device distribution, in each place of system, meets regulation requirement and system transient modelling voltage stabilization to maintain each Area Node transient voltage of system.Just because of this, these dynamic passive compensation equipment are different to improving the contribution of system transient modelling voltage stabilization.These dynamic passive compensation equipment of how to evaluate are the key of computing system reactive power reserve to the contribution of system transient modelling voltage stabilization.The present invention proposes a kind of standby optimization method of dynamic reactive that improves alternating current-direct current electrical network Transient Voltage Stability.Research shows can effectively improve alternating current-direct current electrical network Transient Voltage Stability by the standby optimization method of the dynamic reactive that adopts the present invention to propose.

Summary of the invention

In order to overcome above-mentioned the deficiencies in the prior art, the invention provides a kind of standby optimization method of dynamic reactive that improves alternating current-direct current electrical network Transient Voltage Stability, for improving multi-feed HVDC electrical network Transient Voltage Stability level, provide aid decision support, to improving extensive alternating current-direct current electrical network Transient Voltage Stability nargin, foundation is sent, unimpeded electric power transfer passage between receiving end, promote AC-HVDC passage conveying capacity, improve economy and the quality of power supply of operation of power networks, be all significant.

In order to realize foregoing invention object, the present invention takes following technical scheme:

The invention provides a kind of standby optimization method of dynamic reactive that improves alternating current-direct current electrical network Transient Voltage Stability, said method comprising the steps of:

Step 1: determine the critical failure set and the key node set that affect Transient Voltage Stability in Electric Power System, and successively node is sorted;

Step 2: adjust idle the exerting oneself of dynamic passive compensation equipment, and calculate the trace sensitivity of dynamic passive compensation equipment;

Step 3: m dynamic passive compensation equipment is sorted, and calculate the weight coefficient of dynamic passive compensation equipment;

Step 4: calculate dynamic passive compensation equipment sparing capacity, set up the standby Optimized model of dynamic reactive, and solve the standby Optimized model of this dynamic reactive.

Described step 1 comprises the following steps:

Step 1-1: electric power system is carried out to fault scanning, determine the critical failure set that affects Transient Voltage Stability in Electric Power System according to the serious situation of fault, and determine key node set according to each node voltage level between age at failure;

Step 1-2: successively node is sorted according to the serious situation of fault;

The node of prioritization generation voltage transient unstability, according to node minimum voltage and the sequence of unstability speed; For recovering stable fault, relatively the voltage of each node returns to the time more than 0.8pu, descending sequence;

Step 1-3: the sequence numerical value by each node under different faults is added, more ascending arrangement, thereby obtains node sequencing, is key node the node determination coming above.

Dynamic passive compensation equipment in described step 2 comprises generator, Static Var Compensator SVC and STATCOM STATCOM.

Described step 2 specifically comprises the following steps:

Step 2-1: adjust respectively the idle of each dynamic passive compensation equipment and exert oneself, and critical failure is carried out to time-domain-simulation again;

Step 2-2: for certain fault F _l, single key node i, the trace sensitivity TSI of calculating dynamic passive compensation equipment j _{l, i, j};

Step 2-3: for certain fault F _l, a plurality of key nodes, the trace sensitivity TSI of calculating dynamic passive compensation equipment j _l,j;

Step 2-4: for a plurality of faults, a plurality of nodes, the trace sensitivity TSI of calculating dynamic passive compensation equipment j _j.

Described in dynamic passive compensation equipment dynamic passive compensation equipment dynamic passive compensation equipment in step 2-2, TSI _{l, i, j}be expressed as:

${\mathrm{TSI}}_{l,i,j}=\underset{k=1}{\overset{N_k}{\mathrm{\&Sigma;}}}\left(\frac{V_{i,l}(t_k,{\mathrm{<figure-callout\; id="0"\; label="Q\; j"\; filenames="HDA0000453412800000032.png,HDA0000453412800000041.png"\; state="\{\{state\}\}">Q</figure-callout>}}_j+\mathrm{\&Delta;}{Q}_j)-V_{i,l}(t_k,Q_{j0})}{\mathrm{\&Delta;}{Q}_{\mathrm{Rj}}}\right)---\left(1\right)$

Wherein, j=1,2 ..., m; N _kfor total number of sample points; t _kfor the sampling time; Q _j0initial idle exerting oneself for dynamic passive compensation equipment j; Δ Q _jfor adjusting the idle variable quantity of exerting oneself of dynamic passive compensation equipment j; Δ Q _rjreactive Power Reserve variable quantity for dynamic passive compensation equipment j; V _i,l(t _k, Q _j0+ Δ Q _j) for adjusting after idle the exerting oneself of dynamic passive compensation equipment j, at fault F _lunder, the voltage of node i is at sampling instant t _ktime value; For adjusting before idle the exerting oneself of dynamic passive compensation equipment j, at fault F _lunder, the voltage of node i is at sampling instant t _ktime value.

In described step 2-3, TSI _l,jbe expressed as:

${\mathrm{TSI}}_{l,j}=\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{\mathrm{TSI}}_{l,i,j}---\left(2\right)$

Wherein, n is key node sum.

In described step 2-4, TSI _jbe expressed as:

${\mathrm{TSI}}_j=\underset{l=1}{\overset{N_l}{\mathrm{\&Sigma;}}}{\mathrm{TSI}}_{l,j}---\left(3\right)$

Wherein, N _lfor critical failure sum.

Described step 3 comprises the following steps:

Step 3-1: according to trace sensitivity index TSI _jm dynamic passive compensation equipment is sorted, TSI _jit is maximum to the percentage contribution of Transient Voltage Stability that maximum characterizes this dynamic passive compensation equipment, and the dynamic passive compensation equipment that percentage contribution is large reserves more Reactive Power Reserve amount;

Step 3-2: with TSI _jmaximum of T SI _maxfor benchmark, normalized TSI _j, the weight coefficient p of calculating dynamic passive compensation equipment _j, have:

p _j＝TSI _j/TSI _max （4）。

Described step 4 comprises the following steps:

Step 4-1: calculate dynamic passive compensation equipment sparing capacity;

Dynamic passive compensation equipment sparing capacity Q _rTrepresent, its expression formula is:

$Q_{\mathrm{RT}}=\underset{j=1}{\overset{m}{\mathrm{\&Sigma;}}}{p}_j(Q_{\mathrm{gj}\max }-Q_{\mathrm{gj}})---\left(5\right)$

Wherein, Q _gjmaxfor the idle upper limit of exerting oneself of dynamic passive compensation equipment j, Q _gjcurrent idle exerting oneself for dynamic passive compensation equipment j;

Step 4-2: to improve dynamic passive compensation equipment sparing capacity Q _rTas the standby optimization aim of dynamic reactive, set up the standby Optimized model of dynamic reactive;

Step 4-3: adopt the standby Optimized model of this dynamic reactive of genetic algorithm for solving.

The target function of the standby Optimized model of described dynamic reactive is;

$\max Q_{\mathrm{RT}}=\underset{j=1}{\overset{m}{\mathrm{\&Sigma;}}}{p}_j(Q_{\mathrm{gj}\max }-Q_{\mathrm{gj}})---\left(6\right);$

The constraints of the standby Optimized model of described dynamic reactive comprises power flow equation constraint and variable bound; Described variable bound is control variables constraint and state variable constrain;

In the standby Optimized model of dynamic reactive, meritorious the exerting oneself of each node all meets following power flow equation with idle exerting oneself, and has:

$\left\{\begin{array}{c}{P}_{\mathrm{Gi}}-P_{\mathrm{Li}}-P_{\mathrm{ti}\left(\mathrm{dc}\right)}-V_i\underset{r=1}{\overset{n}{\mathrm{\&Sigma;}}}{V}_r(G_{\mathrm{ir}}\cos {\mathrm{\&delta;}}_{\mathrm{ir}}+B_{\mathrm{ir}}\sin {\mathrm{\&delta;}}_{\mathrm{ir}})=0\\ Q_{\mathrm{Gi}}+Q_{\mathrm{Ci}}-Q_{\mathrm{Li}}-Q_{\mathrm{ti}\left(\mathrm{dc}\right)}-V_i\underset{r=1}{\overset{n}{\mathrm{\&Sigma;}}}{V}_r(G_{\mathrm{ir}}\sin {\mathrm{\&delta;}}_{\mathrm{ir}}-B_{\mathrm{ir}}\cos {\mathrm{\&delta;}}_{\mathrm{ir}})=0\end{array}\right.---\left(7\right)$

Wherein, P _giand Q _gibeing respectively the meritorious of generators in power systems node exerts oneself and idle exerting oneself; P _liand Q _libeing respectively the meritorious of load bus exerts oneself and idle exerting oneself; Q _cireactive compensation capacity for node; P _{ti (dc)}and Q _{ti (dc)}be respectively meritorious input and the idle input of direct current node; G _ijand B _ijthe electricity being respectively between node i, r is led and susceptance; V _iand V _rbe respectively the voltage of node i, r; δ _irfor the phase difference of voltage between node i, r;

1) node i is on rectification side change of current bus, P _{ti (dc)}and Q _{ti (dc)}be expressed as:

$\left\{\begin{array}{c}{P}_{\mathrm{ti}\left(\mathrm{dc}\right)}=k_p{U}_{\mathrm{dR}}{I}_d\\ Q_{\mathrm{ti}\left(\mathrm{dc}\right)}=k_p{I}_d\sqrt{{\left(\frac{3\sqrt{2}}{\mathrm{\&pi;}{K}_{\mathrm{dR}}}b{V}_R\right)}^2-U_{\mathrm{dR}}^2}\end{array}\right.---\left(8\right)$

Wherein, k _pnumber of poles for converter; U _dRfor rectification side direct voltage; I _dfor DC line electric current; K _dRfor rectification side converter transformer no-load voltage ratio; B is 6 pulse wave cascaded bridges numbers of every utmost point; V _rac bus voltage magnitude for rectification side;

2) node i is on inversion side change of current bus, P _{ti (dc)}and Q _{ti (dc)}be expressed as:

$\left\{\begin{array}{c}{P}_{\mathrm{ti}\left(\mathrm{dc}\right)}={-k}_p{U}_{\mathrm{dI}}{I}_d\\ Q_{\mathrm{ti}\left(\mathrm{dc}\right)}=k_p{I}_d\sqrt{{\left(\frac{3\sqrt{2}}{\mathrm{\&pi;}{K}_{\mathrm{dI}}}b{V}_I\right)}^2-U_{\mathrm{dI}}^2}\end{array}\right.---\left(9\right)$

Wherein, U _dIfor inversion side direct voltage; K _dIfor inversion side converter transformer no-load voltage ratio; V _iac bus voltage magnitude for inversion side;

Control variables constraint is as follows:

$\left\{\begin{array}{c}{V}_{\mathrm{Gi}\min }\&le;V_{\mathrm{Gi}}\&le;V_{\mathrm{Gi}\max },i=\mathrm{1,2},...,N_G\\ V_{\mathrm{SVCg}\min \&le;}{V}_{\mathrm{SVCg}}\&le;V_{\mathrm{SVCg}\max },g=\mathrm{1,2},...,N_{\mathrm{SVC}}\\ V_{\mathrm{SVGh}\min \&le;}{V}_{\mathrm{SVGh}}\&le;V_{\mathrm{SVGh}\max },h=\mathrm{1,2},...,N_{\mathrm{SVG}}\\ Q_{\mathrm{Cj}\min \&le;}{Q}_{\mathrm{Cj}}\&le;Q_{\mathrm{Cj}\max },j=\mathrm{1,2},...,N_C\\ T_{k\min }\&le;T_k\&le;T_{k\max },k=\mathrm{1,2},...,N_T\\ U_{\mathrm{dl}\min }\&le;U_{\mathrm{dl}}\&le;U_{\mathrm{dl}\max },l=\mathrm{1,2},...,N_{\mathrm{dc}}\\ I_{\mathrm{dm}\min }\&le;I_{\mathrm{dm}}\&le;I_{\mathrm{dm}\max },m=\mathrm{1,2},...,N_{\mathrm{dc}}\\ P_{\mathrm{dn}\min }\&le;P_{\mathrm{dn}}\&le;P_{\mathrm{dn}\max },n=\mathrm{1,2},...,N_{\mathrm{dc}}\\ {\mathrm{\&theta;}}_{\mathrm{dr}\min }\&le;{\mathrm{\&theta;}}_{\mathrm{dr}}\&le;{\mathrm{\&theta;}}_{\mathrm{dr}\max },r=\mathrm{1,2},...,N_{\mathrm{dc}}\end{array}\right.$

Wherein, N _g, N _sVC, N _sVG, N _c, N _tand N _dcbe respectively generator nodes, SVG nodes, STATCOM nodes, shunt capacitor nodes, transformer application of adjustable tap number and DC network nodes; V _gifor the terminal voltage of generator node, V _giminand V _gimaxbe respectively V _gilower limit and higher limit; V _sVCgfor the terminal voltage of SVC node, V _sVCgminand V _sVCgmaxbe respectively V _sVCglower limit and higher limit; V _sVGhfor the terminal voltage of STATCOM node, V _sVGhminand V _sVGhmaxbe respectively V _sVGhlower limit and higher limit; Q _cjfor the compensation capacity of Shunt Capacitor Unit, Q _cjminand Q _cjmaxbe respectively Q _cjlower limit and higher limit; T _kfor transformer application of adjustable tap, T _kminand T _kmaxbe respectively T _klower limit and higher limit; U _dl, I _dm, P _dnand θ _drbe respectively converter control voltage, control electric current, power ratio control and pilot angle, U _dlminand U _dlmax, I _dmminand I _dmmax, P _dnminand P _dnmax, θ _drminand θ _drmaxrepresent respectively corresponding lower limit and higher limit;

State variable constrain is as follows:

$\left\{\begin{array}{c}{Q}_{\mathrm{Gi}\min }\&le;Q_{\mathrm{Gi}}\&le;Q_{\mathrm{Gi}\max },i=\mathrm{1,2},...,N_G\\ B_{\mathrm{SVCg}\min }\&le;B_{\mathrm{SVCg}}\&le;B_{\mathrm{SVCg}\max },g=\mathrm{1,2},...,N_{\mathrm{SVC}}\\ I_{\mathrm{SVGh}\min }\&le;I_{\mathrm{SVGh}}\&le;I_{\mathrm{SVGh}\max },h=\mathrm{1,2},...,N_{\mathrm{SVG}}\\ V_{\mathrm{Lp}\min }\&le;V_{\mathrm{Lp}}\&le;V_{\mathrm{Lp}\max },p=\mathrm{1,2},...,N_L\end{array}\right.---\left(11\right)$

Wherein, N _lfor load bus number; Q _gifor generator node is idle, exert oneself, B _sVCgfor SVC susceptance, I _sVGhfor STATCOM current amplitude, Q _giminand Q _gimaxbe respectively Q _gilower limit and higher limit; B _sVCgminand B _sVCgmaxbe respectively B _sVCglower limit and higher limit; I _sVGhminand I _sVGhmaxbe respectively I _sVGhlower limit and higher limit; V _lpfor load bus voltage magnitude, V _lpminand V _lpmaxbe respectively V _lplower limit and higher limit.

Compared with prior art, beneficial effect of the present invention is:

1. for the feature of multi-feed HVDC system, the invention provides a kind of standby optimization method of dynamic reactive that improves alternating current-direct current electrical network Transient Voltage Stability, reasonable arrangement dynamic reactive reserve capacity configuration, can effectively improve direct current commutation lsafety level, meet electrical network transient voltage safety requirements;

2. compare with the traditional Reactive Power Reserve optimization method based on static, this method has been considered the dynamic characteristic of system in detail, can determine more exactly dynamic passive compensation equipment sparing capacity, for the optimization operation of electrical network provides basis;

This method is analyzed by time-domain-simulation, can be quick and easy, determine exactly the weight coefficient of each dynamic passive compensation equipment, can be applicable to the standby optimization of dynamic reactive of large-scale electrical power system, the algorithm that has overcome the optimization of conventional electric power system dynamic reactive-load can only be applied to the shortcoming of mini system;

The present invention provides aid decision support for improving multi-feed HVDC electrical network Transient Voltage Stability level, to improving extensive alternating current-direct current electrical network Transient Voltage Stability nargin, foundation is sent, unimpeded electric power transfer passage between receiving end, promote AC-HVDC passage conveying capacity, economy and the quality of power supply of improving operation of power networks, be all significant.

Accompanying drawing explanation

Fig. 1 is the standby optimization method flow chart of dynamic reactive that improves alternating current-direct current electrical network Transient Voltage Stability;

Fig. 2 adopts the standby Optimized model flow chart of genetic algorithm for solving dynamic reactive;

Fig. 3 is 3 machine 10 node regulation test ac and dc systems schematic diagrames in the invention process;

Fig. 4 is the voltage curve of node 1, node 2, node 4 and node 5 in 3 machine 10 node regulation test ac and dc systemses;

Fig. 5 is the node 3 in 3 machine 10 node regulation test ac and dc systemses, the voltage curve of node 6～node 10;

Fig. 6 is the set end voltage that changes generator G3, investigates the change in voltage curve chart of fault lower node 3;

Fig. 7 is the set end voltage that changes generator G3, investigates the change in voltage curve chart of fault lower node 6;

Fig. 8 is the set end voltage that changes generator G3, investigates the change in voltage curve chart of fault lower node 7;

Fig. 9 is the set end voltage that changes generator G3, investigates the change in voltage curve chart of fault lower node 8;

Figure 10 is the set end voltage that changes generator G3, investigates the change in voltage curve chart of fault lower node 9;

Figure 11 is the set end voltage that changes generator G3, investigates the change in voltage curve chart of fault lower node 10;

Figure 12 is the set end voltage that changes generator G3, investigates the idle change curve that under fault, generator G3 sends;

Figure 13 investigates initial idle the exerting oneself of SVC under fault to change the change in voltage curve chart of front and back node 3;

Figure 14 investigates initial idle the exerting oneself of SVC under fault to change the change in voltage curve chart of front and back node 6;

Figure 15 investigates initial idle the exerting oneself of SVC under fault to change the change in voltage curve chart of front and back node 7;

Figure 16 investigates initial idle the exerting oneself of SVC under fault to change the change in voltage curve chart of front and back node 8;

Figure 17 investigates initial idle the exerting oneself of SVC under fault to change the change in voltage curve chart of front and back node 9;

Figure 18 investigates initial idle the exerting oneself of SVC under fault to change the change in voltage curve chart of front and back node 10;

Figure 19 investigates initial idle the exerting oneself of SVC under fault to change the idle change curve of exerting oneself of front and back SVC;

Figure 20 is node 3(Generator end before and after optimizing) voltage curve;

Figure 21 is node 6 voltage curves before and after optimizing.

Embodiment

Below in conjunction with accompanying drawing, the present invention is described in further detail.

Embodiment

For 3 machine 10 node systems, the embodiment of the present invention makes 5 times alternating current interconnections between bus 5 and 6 into 2 times alternating current interconnections and 1 time bipolar direct current transmission line, because the direction of the active power of former alternating current circuit is to flow to node 6 from node 5, so establish node 5 for rectification side, 6 is inversion side, as shown in Figure 3.The reactive power absorbing due to direct current system is larger, so the capacity that configured respectively on node 6 is ± SVC of 180MVar and the capacitor group that capacity is 1000MVar that the every pool-size of this capacitor group is 100MVar, totally 10 groups.In addition, unit, load and the electric network data of reservation original system are constant.Form thus the correction test macro of alternating current-direct current series-parallel connection transmission of electricity.

This system is carried out to fault scanning, determine and threaten the stable critical failure set of system voltage.For the validity of TSI index is described easily, this example is only investigated the most serious N-1 fault, when failure mode is t=1s, an alternating current interconnection of 6 of node 5～nodes is at the permanent short trouble of node 6 side generation three-phase, 0.09s tripping faulty line node 6 side switches after fault, 0.1s tripping faulty line node 5 side switches.Fig. 4 and Fig. 5 be each node voltage curve under fault for this reason, and as can be seen from the figure, after failure removal, it is maximum and recover the slowest that the voltage of node 3, node 6, node 7, node 8, node 9 and node 10 falls amplitude, and therefore selecting these 6 nodes is key node.

For this fault, the generator reactive of computing node 3 is exerted oneself and the idle trace sensitivity TSI exerting oneself of node 6SVC respectively.

The set end voltage initial value of setting generator G3 is respectively 1.011p.u. and 1.021p.u., and the change in voltage curve of simulation calculation investigation fault lower node 3, node 6, node 7, node 8, node 9 and node 10 and the idle change curve that generator G3 sends are respectively as shown in Fig. 6～Figure 12.According to formula (3), calculating the idle trace sensitivity index TSI changing that exerts oneself of generator G3 under investigation fault is 0.017.

Set initial idle the exerting oneself of SVC and be respectively 0 and 120MVar capacitive reactive power, simulation calculation is investigated the change in voltage curve of fault lower node 3, node 6, node 7, node 8, node 9 and node 10 and idle change curve that SVC sends respectively as shown in Figure 13～Figure 19.According to formula (3), calculating the idle trace sensitivity index TSI changing that exerts oneself of SVC under investigation fault is 0.701.

Before and after the standby optimization of dynamic reactive, control variables contrast is as shown in table 1.Before and after the standby optimization of dynamic reactive, reactive power reserve contrast is as shown in table 2.As seen from Table 1, the reactive power reserve after optimization has improved (422.4-230.4)/230.4*100%=83.3% than optimizing precontract.

Table 1

Control variables	Before optimization	After optimization
			V g3（p.u.)	1.01	1.04
The group number (group) that node 6 shunt capacitors drop into	10	7
			SVC is idle to exert oneself, and (capacitive is for just, MVar)	0	-180

Table 2

Investigate the most serious N-1 fault, when failure mode is t=0.1s, an alternating current interconnection of 6 of node 5～nodes is at the permanent short trouble of node 6 side generation three-phase, 0.09s tripping faulty line node 6 side switches after fault, 0.1s tripping faulty line node 5 side switches.Figure 20 and Figure 21 are respectively generator G3 set end voltage and node 6 voltage curves, as can be seen from the figure, after optimizing, the transient voltage of system recovers than fast before optimizing, and the optimized algorithm that this explanation adopts this problem to propose can effectively improve the Enhancement of Transient Voltage Stability of electrical network.

Finally should be noted that: above embodiment is only in order to illustrate that technical scheme of the present invention is not intended to limit, although the present invention is had been described in detail with reference to above-described embodiment, those of ordinary skill in the field are to be understood that: still can modify or be equal to replacement the specific embodiment of the present invention, and do not depart from any modification of spirit and scope of the invention or be equal to replacement, it all should be encompassed in the middle of claim scope of the present invention.

Claims (10)

1. the standby optimization method of dynamic reactive that improves alternating current-direct current electrical network Transient Voltage Stability, is characterized in that: said method comprising the steps of:

Step 1: determine the critical failure set and the key node set that affect Transient Voltage Stability in Electric Power System, and successively node is sorted;

Step 2: adjust idle the exerting oneself of dynamic passive compensation equipment, and calculate the trace sensitivity of dynamic passive compensation equipment;

Step 3: m dynamic passive compensation equipment is sorted, and calculate the weight coefficient of dynamic passive compensation equipment;

Step 4: calculate dynamic passive compensation equipment sparing capacity, set up the standby Optimized model of dynamic reactive, and solve the standby Optimized model of this dynamic reactive.

2. the standby optimization method of dynamic reactive of raising alternating current-direct current electrical network Transient Voltage Stability according to claim 1, is characterized in that: described step 1 comprises the following steps:

Step 1-1: electric power system is carried out to fault scanning, determine the critical failure set that affects Transient Voltage Stability in Electric Power System according to the serious situation of fault, and determine key node set according to each node voltage level between age at failure;

Step 1-2: successively node is sorted according to the serious situation of fault;

The node of prioritization generation voltage transient unstability, according to node minimum voltage and the sequence of unstability speed; For recovering stable fault, relatively the voltage of each node returns to the time more than 0.8pu, descending sequence;

Step 1-3: the sequence numerical value by each node under different faults is added, more ascending arrangement, thereby obtains node sequencing, is key node the node determination coming above.

3. the standby optimization method of dynamic reactive of raising alternating current-direct current electrical network Transient Voltage Stability according to claim 1, is characterized in that: the dynamic passive compensation equipment in described step 2 comprises generator, Static Var Compensator SVC and STATCOM STATCOM.

4. the standby optimization method of dynamic reactive of raising alternating current-direct current electrical network Transient Voltage Stability according to claim 3, is characterized in that: described step 2 specifically comprises the following steps:

Step 2-1: adjust respectively the idle of each dynamic passive compensation equipment and exert oneself, and critical failure is carried out to time-domain-simulation again;

Step 2-2: for certain fault F _l, single key node i, the trace sensitivity TSI of calculating dynamic passive compensation equipment j _{l, i, j};

Step 2-3: for certain fault F _l, a plurality of key nodes, the trace sensitivity TSI of calculating dynamic passive compensation equipment j _l,j;

Step 2-4: for a plurality of faults, a plurality of nodes, the trace sensitivity TSI of calculating dynamic passive compensation equipment j _j.

5. the standby optimization method of dynamic reactive of raising alternating current-direct current electrical network Transient Voltage Stability according to claim 4, is characterized in that: in described step 2-2, and TSI _{l, i, j}be expressed as:

${\mathrm{TSI}}_{l,i,j}=\underset{k=1}{\overset{N_k}{\mathrm{\&Sigma;}}}\left(\frac{V_{i,l}(t_k,Q_{j0}+\mathrm{\&Delta;}{Q}_j)-V_{i,l}(t_k,Q_{j0})}{\mathrm{\&Delta;}{Q}_{\mathrm{Rj}}}\right)---\left(1\right)$

Wherein, j=1,2 ..., m; N _kfor total number of sample points; t _kfor the sampling time; Q _j0initial idle exerting oneself for dynamic passive compensation equipment j; Δ Q _jfor adjusting the idle variable quantity of exerting oneself of dynamic passive compensation equipment j; Δ Q _rjreactive Power Reserve variable quantity for dynamic passive compensation equipment j; V _i,l(t _k, Q _j0+ Δ Q _j) for adjusting after idle the exerting oneself of dynamic passive compensation equipment j, at fault F _lunder, the voltage of node i is at sampling instant t _ktime value; For adjusting before idle the exerting oneself of dynamic passive compensation equipment j, at fault F _lunder, the voltage of node i is at sampling instant t _ktime value.

6. the standby optimization method of dynamic reactive of raising alternating current-direct current electrical network Transient Voltage Stability according to claim 4, is characterized in that: in described step 2-3, and TSI _l,jbe expressed as:

${\mathrm{TSI}}_{l,j}=\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{\mathrm{TSI}}_{l,i,j}---\left(2\right)$

Wherein, n is key node sum.

7. the standby optimization method of dynamic reactive of raising alternating current-direct current electrical network Transient Voltage Stability according to claim 4, is characterized in that: in described step 2-4, and TSI _jbe expressed as:

${\mathrm{TSI}}_j=\underset{l=1}{\overset{N_l}{\mathrm{\&Sigma;}}}{\mathrm{TSI}}_{l,j}---\left(3\right)$

Wherein, N _lfor critical failure sum.

8. the standby optimization method of dynamic reactive of raising alternating current-direct current electrical network Transient Voltage Stability according to claim 1, is characterized in that: described step 3 comprises the following steps:

Step 3-1: according to trace sensitivity index TSI _jm dynamic passive compensation equipment is sorted, TSI _jit is maximum to the percentage contribution of Transient Voltage Stability that maximum characterizes this dynamic passive compensation equipment, and the dynamic passive compensation equipment that percentage contribution is large reserves Reactive Power Reserve amount;

Step 3-2: with TSI _jmaximum of T SI _maxfor benchmark, normalized TSI _j, the weight coefficient p of calculating dynamic passive compensation equipment _j, have:

p _j＝TSI _j/TSI _max （4）。

9. the standby optimization method of dynamic reactive of raising alternating current-direct current electrical network Transient Voltage Stability according to claim 1, is characterized in that: described step 4 comprises the following steps:

Step 4-1: calculate dynamic passive compensation equipment sparing capacity;

Dynamic passive compensation equipment sparing capacity Q _rTrepresent, its expression formula is:

$Q_{\mathrm{RT}}=\underset{j=1}{\overset{m}{\mathrm{\&Sigma;}}}{p}_j(Q_{\mathrm{gj}\max }-Q_{\mathrm{gj}})---\left(5\right)$

Wherein, Q _gjmaxfor the idle upper limit of exerting oneself of dynamic passive compensation equipment j, Q _gjcurrent idle exerting oneself for dynamic passive compensation equipment j;

Step 4-2: to improve dynamic passive compensation equipment sparing capacity Q _rTas the standby optimization aim of dynamic reactive, set up the standby Optimized model of dynamic reactive;

Step 4-3: adopt the standby Optimized model of this dynamic reactive of genetic algorithm for solving.

10. the standby optimization method of dynamic reactive of raising alternating current-direct current electrical network Transient Voltage Stability according to claim 9, is characterized in that: the target function of the standby Optimized model of described dynamic reactive is;

$\max Q_{\mathrm{RT}}=\underset{j=1}{\overset{m}{\mathrm{\&Sigma;}}}{p}_j(Q_{\mathrm{gj}\max }-Q_{\mathrm{gj}})---\left(6\right);$

The constraints of the standby Optimized model of described dynamic reactive comprises power flow equation constraint and variable bound; Described variable bound is control variables constraint and state variable constrain;

In the standby Optimized model of dynamic reactive, meritorious the exerting oneself of each node all meets following power flow equation with idle exerting oneself, and has:

$\left\{\begin{array}{c}{P}_{\mathrm{Gi}}-P_{\mathrm{Li}}-P_{\mathrm{ti}\left(\mathrm{dc}\right)}-V_i\underset{r=1}{\overset{n}{\mathrm{\&Sigma;}}}{V}_r(G_{\mathrm{ir}}\cos {\mathrm{\&delta;}}_{\mathrm{ir}}+B_{\mathrm{ir}}\sin {\mathrm{\&delta;}}_{\mathrm{ir}})=0\\ Q_{\mathrm{Gi}}+Q_{\mathrm{Ci}}-Q_{\mathrm{Li}}-Q_{\mathrm{ti}\left(\mathrm{dc}\right)}-V_i\underset{r=1}{\overset{n}{\mathrm{\&Sigma;}}}{V}_r(G_{\mathrm{ir}}\sin {\mathrm{\&delta;}}_{\mathrm{ir}}-B_{\mathrm{ir}}\cos {\mathrm{\&delta;}}_{\mathrm{ir}})=0\end{array}\right.---\left(7\right)$

Wherein, P _giand Q _gibeing respectively the meritorious of generators in power systems node exerts oneself and idle exerting oneself; P _liand Q _libeing respectively the meritorious of load bus exerts oneself and idle exerting oneself; Q _cireactive compensation capacity for node; P _{ti (dc)}and Q _{ti (dc)}be respectively meritorious input and the idle input of direct current node; G _ijand B _ijthe electricity being respectively between node i, r is led and susceptance; V _iand V _rbe respectively the voltage of node i, r; δ _irfor the phase difference of voltage between node i, r;

1) node i is on rectification side change of current bus, P _{ti (dc)}and Q _{ti (dc)}be expressed as:

$\left\{\begin{array}{c}{P}_{\mathrm{ti}\left(\mathrm{dc}\right)}=k_p{U}_{\mathrm{dR}}{I}_d\\ Q_{\mathrm{ti}\left(\mathrm{dc}\right)}=k_p{I}_d\sqrt{{\left(\frac{3\sqrt{2}}{\mathrm{\&pi;}{K}_{\mathrm{dR}}}b{V}_R\right)}^2-U_{\mathrm{dR}}^2}\end{array}\right.---\left(8\right)$

Wherein, k _pnumber of poles for converter; U _dRfor rectification side direct voltage; I _dfor DC line electric current; K _dRfor rectification side converter transformer no-load voltage ratio; B is 6 pulse wave cascaded bridges numbers of every utmost point; V _rac bus voltage magnitude for rectification side;

2) node i is on inversion side change of current bus, P _{ti (dc)}and Q _{ti (dc)}be expressed as:

$\left\{\begin{array}{c}{P}_{\mathrm{ti}\left(\mathrm{dc}\right)}={-k}_p{U}_{\mathrm{dI}}{I}_d\\ Q_{\mathrm{ti}\left(\mathrm{dc}\right)}=k_p{I}_d\sqrt{{\left(\frac{3\sqrt{2}}{\mathrm{\&pi;}{K}_{\mathrm{dI}}}b{V}_I\right)}^2-U_{\mathrm{dI}}^2}\end{array}\right.---\left(9\right)$

Wherein, U _dIfor inversion side direct voltage; K _dIfor inversion side converter transformer no-load voltage ratio; V _iac bus voltage magnitude for inversion side;

Control variables constraint is as follows:

$\left\{\begin{array}{c}{V}_{\mathrm{Gi}\min }\&le;V_{\mathrm{Gi}}\&le;V_{\mathrm{Gi}\max },i=\mathrm{1,2},...,N_G\\ V_{\mathrm{SVCg}\min \&le;}{V}_{\mathrm{SVCg}}\&le;V_{\mathrm{SVCg}\max },g=\mathrm{1,2},...,N_{\mathrm{SVC}}\\ V_{\mathrm{SVGh}\min \&le;}{V}_{\mathrm{SVGh}}\&le;V_{\mathrm{SVGh}\max },h=\mathrm{1,2},...,N_{\mathrm{SVG}}\\ Q_{\mathrm{Cj}\min \&le;}{Q}_{\mathrm{Cj}}\&le;Q_{\mathrm{Cj}\max },j=\mathrm{1,2},...,N_C\\ T_{k\min }\&le;T_k\&le;T_{k\max },k=\mathrm{1,2},...,N_T\\ U_{\mathrm{dl}\min }\&le;U_{\mathrm{dl}}\&le;U_{\mathrm{dl}\max },l=\mathrm{1,2},...,N_{\mathrm{dc}}\\ I_{\mathrm{dm}\min }\&le;I_{\mathrm{dm}}\&le;I_{\mathrm{dm}\max },m=\mathrm{1,2},...,N_{\mathrm{dc}}\\ P_{\mathrm{dn}\min }\&le;P_{\mathrm{dn}}\&le;P_{\mathrm{dn}\max },n=\mathrm{1,2},...,N_{\mathrm{dc}}\\ {\mathrm{\&theta;}}_{\mathrm{dr}\min }\&le;{\mathrm{\&theta;}}_{\mathrm{dr}}\&le;{\mathrm{\&theta;}}_{\mathrm{dr}\max },r=\mathrm{1,2},...,N_{\mathrm{dc}}\end{array}\right.$

Wherein, N _g, N _sVC, N _sVG, N _c, N _tand N _dcbe respectively generator nodes, SVG nodes, STATCOM nodes, shunt capacitor nodes, transformer application of adjustable tap number and DC network nodes; V _gifor the terminal voltage of generator node, V _giminand V _gimaxbe respectively V _gilower limit and higher limit; V _sVCgfor the terminal voltage of SVC node, V _sVCgminand V _sVCgmaxbe respectively V _sVCglower limit and higher limit; V _sVGhfor the terminal voltage of STATCOM node, V _sVGhminand V _sVGhmaxbe respectively V _sVGhlower limit and higher limit; Q _cjfor the compensation capacity of Shunt Capacitor Unit, Q _cjminand Q _cjmaxbe respectively Q _cjlower limit and higher limit; T _kfor transformer application of adjustable tap, T _kminand T _kmaxbe respectively T _klower limit and higher limit; U _dl, I _dm, P _dnand θ _drbe respectively converter control voltage, control electric current, power ratio control and pilot angle, U _dlminand U _dlmax, I _dmminand I _dmmax, P _dnminand P _dnmax, θ _drminand θ _drmaxrepresent respectively corresponding lower limit and higher limit;

State variable constrain is as follows:

$\left\{\begin{array}{c}{Q}_{\mathrm{Gi}\min }\&le;Q_{\mathrm{Gi}}\&le;Q_{\mathrm{Gi}\max },i=\mathrm{1,2},...,N_G\\ B_{\mathrm{SVCg}\min }\&le;B_{\mathrm{SVCg}}\&le;B_{\mathrm{SVCg}\max },g=\mathrm{1,2},...,N_{\mathrm{SVC}}\\ I_{\mathrm{SVGh}\min }\&le;I_{\mathrm{SVGh}}\&le;I_{\mathrm{SVGh}\max },h=\mathrm{1,2},...,N_{\mathrm{SVG}}\\ V_{\mathrm{Lp}\min }\&le;V_{\mathrm{Lp}}\&le;V_{\mathrm{Lp}\max },p=\mathrm{1,2},...,N_L\end{array}\right.---\left(11\right)$

Wherein, N _lfor load bus number; Q _gifor generator node is idle, exert oneself, B _sVCgfor SVC susceptance, I _sVGhfor STATCOM current amplitude, Q _giminand Q _gimaxbe respectively Q _gilower limit and higher limit; B _sVCgminand B _sVCgmaxbe respectively B _sVCglower limit and higher limit; I _sVGhminand I _sVGhmaxbe respectively I _sVGhlower limit and higher limit; V _lpfor load bus voltage magnitude, V _lpminand V _lpmaxbe respectively V _lplower limit and higher limit.

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