CN102340140A - A method to automatically and quickly obtain the stability limit and stability control strategy of large-scale interconnected power grid - Google Patents

Abstract

The invention discloses a method for automatically fast calculating the stability limit of a large-scale interconnected power grid and a stability control strategy. Generally, a power grid scheduling running department calculates a power transmission limit and the stability control strategy by using the analysis software of a power system and manually judges the stability of the system according to a time-domain simulation curve by adopting a continuous regulation running way and simultaneously performing large-batch expected failure stability checking. In such a process, relatively more repeated operations and low efficiency are caused. In the method for automatically fast calculating the stability limit of the large-scale interconnected power grid and the stability control strategy, a corresponding strategy is formulated according to the process of calculating the stability limit and the stability control strategy every day by power grid running way personnel based on conventional power flow calculation, transient stability calculation and the like for the power system, and total automation is realized for the calculation of the stability limit and the stability control strategy, so the method totally can replace the process of manually calculating the stability limit of a power transmission section and the stability control strategy, and is remarkably advanced in the power transmission limit of a large-scale power grid with low calculation convergence.

Description

A kind of method of asking for large-scale interconnected power system stability limit and steady control strategy automatically fast

Technical field

The present invention relates to power system operation mode and calculate, especially ask for the calculating of transmission cross-section stability limit and steady control strategy.

Background technology

The main method of the current calculating stabilization of power grids limit has: deterministic method for solving and based on two big types of the method for solving of probability.Wherein deterministic method mainly comprises the linear distribution factorization method, repeats trend method, continuous tide method, optimal load flow method, Sensitivity Analysis Method etc.

The linear distribution factor can only be used for the less demanding occasion of computational solution precision, like planning and designing etc.Repeat the trend method and can take into account the voltage and the idle influence to stability limit of system, can easily consider various scleronomic constraints, result of calculation can reflect actual operating state preferably; Just the workload of the each adjustment of trend is loaded down with trivial details.The continuous tide method is as research voltage stable instrument, stressed to estimate-proofreaies and correct-step-length controls, and with the way of search of the actual electric network transient stability limit certain difference arranged.Optimal load flow can be handled various constraints such as steady stability, transient stability, small interference stability in theory, can realize generating electricity in larger scope and Load distribution optimization, and result of calculation is more accurate; But the optimized operation that is obtained point is an ideal results, in fact possibly can't realize, and when the considering transient scleronomic constraint, a lot of difficulties arranged, and the convergence that extensive equation group is found the solution is difficult to guarantee.Sensitivity Analysis Method is not a kind of computational methods of independently stability limit, and it need be the basis with certain stability limit result of calculation; Normally used first order modeling has only when institute's research object linearity is very high just effectively in the practical application, and stability limit is a nonlinear model in essence.Also be in the middle of the theoretical research based on the probability method major part, one segment distance still arranged from practical application.

Dispatching of power netwoks operational mode department is when calculating the stability limit of considering transient scleronomic constraint; Common electrification system emulation software for calculation; Under the prerequisite that guarantees total system generating-load whole machine balancing; Held generator output, payload to specify the through-put power of transmission cross-section through adjusting repeatedly to send, and carry out large batch of fault and check, provided the judgement of the stability of a system by the manual work of time-domain-simulation curve with change.The adjustment of the trend mode of carrying out repeatedly that this process need is artificial, declare surely through simulation curve, complex steps, computational efficiency is lower, has expended huge manpower and time cost.Add the calculating of asking for of steady control strategy, the The whole calculations process is very complicated more.Network for poor astringency; The change that state and load tap changer position are moved back in the throwing of generator output, payload, shunt capacitance reactance probably causes trend to calculate even convergence of very difficult convergence; And trend had and separated actual this moment, and current operating point reaches the steady state stability limit point far away.

Summary of the invention

In order to overcome the existing deficiency of calculating the stabilization of power grids limit and steady control strategy process; The present invention provides a kind of new method of asking for large-scale interconnected power system stability limit and steady control strategy automatically fast; This method not only can solve the low problem of dispatching of power netwoks operational mode department calculation stability limit computational efficiency, and can greatly improve the convergence of transient mode trend.

The method of asking for large-scale interconnected power system stability limit and steady control strategy automatically fast that the present invention is corresponding is to be the basis with the conventional trend calculating of electric power system, transient stability calculating etc.; According to the daily calculation stability limit of power system operating mode personnel and ask for the process establishment corresponding strategy of steady control strategy; Transient mode adjustment, trend calculating, the current transmit power calculation of transmission cross-section, reactive power compensation calculating, fault verification, stabilize decision have been realized that through the method for asking for the large-scale interconnected power system transmission of electricity limit and steady control strategy automatically fast automation completely calculates; Thereby can substitute artificial calculating transmission cross-section stability limit fully and ask for the tactful process of steady control, especially when the transmission of electricity limit of the catenet of asking for poor astringency, have significant advantage.

The main feature of this method has: (1) can provide transient mode automatically according to electrical network feature and relevant the setting; (2) can consider reactive power compensator, adjust the voltage of associated bus automatically; (3) can help to improve the strategy of stability limit according to preset steady control Policy Filtering; (4) to the characteristics of large-scale interconnected power system transient mode trend poor astringency, design the constringent method of raising trend, had significant advantage when the stability limit of the electrical network more than asking for 15000 node levels and steady control strategy; (5) can the criterions that the electrical network of zones of different is used different severe grades be set according to criterion and declare surely the stable information that the system that provides is detailed automatically; (6) can consider of the influence of other transmission cross-sections to the host computer transmission cross-section; (7) can consider of the influence of main transmission cross-section both sides busbar voltage to the transmission of electricity limit.

Description of drawings

Fig. 1 is for calculating the method flow diagram of large-scale interconnected power system stability limit.

The method flow that Fig. 2 asks for for steady control strategy.

Fig. 3 is the method flow of fault verification stabilize decision.

Fig. 4 throws the method flow that moves back automatically for reactive power compensator.

Fig. 5 is the transmission cross-section sketch map.

Embodiment

The present invention for the specific embodiments that solution prior art problem is adopted is:

Before the maximum ability to transmit electricity of program search transmission cross-section, need earlier by staff's intended target section, the target setting section estimate limiting value.Estimate the maximum ability to transmit electricity of the transmission cross-section of the appointment that limiting value estimates for the staff, estimate limiting value if the through-put power of the transmission cross-section of appointment has surpassed in the program search process, then stop to continue search forward.

As shown in Figure 1, a simple calculation process can be described as (supposes that basic Tidal current system verification is stablized and transmission cross-section power is estimated limiting value above it; Initial adjustment step-length is 1/2nd of a current transmission cross-section through-put power difference of estimating limiting value with it, adjusts mode selection mode two.)：

A. confirm adjustment amount, upgrade the meritorious idle of the generator of participating in the trend adjustment, load.

B. conventional trend is calculated, if do not restrain, then gets into step c; If convergence then gets into step e.

C. the trend result with last time convergence is that initial value recomputates trend, if still do not restrain, then gets back to flow state point last time, reduces to return a after the step-length; If convergence then gets into steps d.

D. forecast failure collection verification if system's unstability is then got back to trend stable operating point last time, reduces to return a after the step-length; If system stability then gets into step e.

E. judge whether current goal section through-put power arrives and estimate limiting value or the adjustment step-length has reached the adjustment precision, promptly export the result, stop to calculate as long as both satisfy one of which; Otherwise get into step f.

F. if instability or trend when aforementioned adjustment, not occurring does not thoroughly restrain situation and then keep former step-length, be basis with current trend stable operating point, growth appointment transmission cross-section through-put power is returned step a; Otherwise, be the basis with current trend stable operating point, reduce step-length, increase and specify the transmission cross-section through-put power, return step a.

Each realization link specific to method has:

(1) transient mode is adjusted automatically.

Mode one: adjustment mode that the direct throwing of adjustment employing of generator load is moved back and generator do not stay to revolve and are equipped with.Select this kind mode for use, need to specify that each adjustment group has all which unit puts into operation, which unit is out of service, which load connecting system, which load log off.Be noted that: to send the new start group of end, to be held the adjustment mode of unit out of service is example, send the summation of exerting oneself of the new generator that drops into of end will equate with the summation of exerting oneself of being held generator out of service as far as possible, exerts oneself normally to guarantee balancing machine.For accelerate solution procedure as far as possible, program is thrown the adjustment object that moves back the power margin maximum earlier according to elder generation's thin principle in thick back, if trend does not restrain or the system check unstability, then selects the adjustment object of second largest power margin again for use during adjustment.The rest may be inferred, and the adjustment object of minimum power nargin has determined the adjustment precision of section power.

Set-up mode two: the mode by fixed step size adjustment is adopted in the power adjustment of generator, load.Specify the meritorious idle adjustment increment of generation load earlier; When increment size is correct time; Expression increases the power of this generating or load, when increment size when negative, expression reduces the power of this generating or load; Program according to current section active power estimate difference and each generator of limiting value with it, the meritorious adjustment incremental computations of load goes out the actual adjustment step-length of each generator, load; In next trend is calculated, revise the power (then being limit value if reach limit value) of corresponding generation load according to the adjustment step-length, shown in (1)-(4), what need explanation is: generator idle of not adjusting PV, PV-PQ node.

$P_{\mathrm{Gi}}^{n+1}=P_{\mathrm{Gi}}^n+k_{\mathrm{GPi}}^{n+1}{\mathrm{\ΔP}}_{\mathrm{Gi}},(P_{\mathrm{Gi}\min }\≤P_{\mathrm{Gi}}^{n+1}\≤P_{\mathrm{Gi}\max })---\left(1\right)$

$Q_{\mathrm{Gi}}^{n+1}=Q_{\mathrm{Gi}}^n+k_{\mathrm{GQi}}^{n+1}{\mathrm{\ΔQ}}_{\mathrm{Gi}},(Q_{\mathrm{Gi}\min }\≤Q_{\mathrm{Gi}}^{n+1}\≤Q_{\mathrm{Gi}\max })---\left(2\right)$

$P_{\mathrm{Lj}}^{n+1}=P_{\mathrm{Lj}}^n+k_{\mathrm{LPj}}^{n+1}{\mathrm{\ΔP}}_{\mathrm{Lj}},(P_{\mathrm{Lj}\min }\≤P_{\mathrm{Lj}}^{n+1}\≤P_{\mathrm{Lj}\max })---\left(3\right)$

$Q_{\mathrm{Lj}}^{n+1}=Q_{\mathrm{Lj}}^n+k_{\mathrm{LQj}}^{n+1}{\mathrm{\ΔQ}}_{\mathrm{Lj}},(Q_{\mathrm{Lj}\min }\≤Q_{\mathrm{Lj}}^{n+1}\≤Q_{\mathrm{Lj}\max })---\left(4\right)$

In formula (1)-(4),

Refer to that respectively generator i the n time is adjusted meritorious, idle; Δ P _Gi, Δ Q _GiThe meritorious idle adjustment increment that refers to generator i respectively;

Refer to the n+1 time meritorious, idle adjustment coefficient of generator i respectively,

The j the n time of referring to respectively load is adjusted meritorious, idle; Δ P _Lj, Δ Q _LjThe meritorious idle adjustment increment of j refers to respectively to load;

The n+1 time meritorious, the idle adjustment coefficient of j that refer to respectively to load,

k _GPi, k _LPjInitial value suc as formula shown in (5), (6).

$k_{\mathrm{GPi}}^0=\frac{P_{\mathrm{CUT}}^{\mathrm{GOAL}}-P^0}{\mathrm{N\ΔP}}{\mathrm{\ΔP}}_{\mathrm{Gi}}---\left(5\right)$

$k_{\mathrm{LPi}}^0=\frac{P_{\mathrm{CUT}}^{\mathrm{GOAL}}-P^0}{\mathrm{N\ΔP}}{\mathrm{\ΔP}}_{\mathrm{Li}}---\left(6\right)$

In formula (5), (6),

Refer to the limiting value of estimating of target section; P ⁰The meritorious transmission value that refers to initial trend target section; The N maximum occurrences is 5, and minimum value is 1, and default value is 2; The computing formula of Δ P is suc as formula (supposing to have n platform generator, a m load to participate in adjustment) shown in (7).

$\mathrm{\ΔP}=\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\left|{\mathrm{\ΔP}}_{\mathrm{Gi}}\right|+\underset{j=1}{\overset{m}{\mathrm{\Σ}}}\left|{\mathrm{\ΔP}}_{\mathrm{Lj}}\right|}{2}---\left(7\right)$

(2) take more to calculate trend near the initial value of true solution

The electric power system tide equation is one group of nonlinear equation, because non linear system is intrinsic, power flow equation existed do not have and separates or multiple solution, and that electrical network feature is set etc. is relevant with scale of power, load level, PV point again for this.Especially the expansion of scale of power, enriching of idle regulating measure makes appearance not have the situation of separating and is tending towards reducing, and the possibility of multiple solution increases on the contrary greatly.This moment initial value to trend separate more significant, different initial values possibly occur at last such as disperse, with different results such as separating, separate more.

Asking in the process of the stabilization of power grids limit and steady control strategy; Former and later two transient modes often gap are little; Especially for large-scale data, the change of indivedual generators, load data is smaller to the whole network global voltage distribution influence, last time the trend result the actual value that calculates near current trend of bus voltage value; Adopt and to restrain the method that the result makes initial value last time and just can obtain reasonable initial value, help converging to rational stable solution.

(3) reactive power compensator is thrown automatically and is moved back

The reactive power compensator here mainly refers to the shunt capacitance reactance.The staff is provided with the voltage upper lower limit value of the bus that hangs with the shunt capacitance reactance; After each trend is calculated and is finished; Operation (hang the situation of organizing the shunt capacitance reactance for bus, program is only operated one group at every turn more) is moved back in throwing according to the relation of bus virtual voltage result of calculation and its voltage upper lower limit value is selected to carry out the shunt capacitance reactance.

As shown in Figure 4, in the Practical Calculation, maximum voltage inspection number of times need be set, avoid the shunt capacitance reactance to throw repeatedly and move back the undying trend calculating that causes.During inspection, can be provided with the trend of middle all operating points of transient mode is all carried out voltage inspection, the trend mode that only also can be provided with when finally reaching maximum ability to transmit electricity is carried out the voltage inspection.

(4) declare automatically surely

When actual electric network is analyzed, possibly use the stability criterion of different severe grades to the bus of different electrical network zones or different electric pressures.The method of asking for large-scale interconnected power system stability limit and steady control strategy has taken into full account this demand.(each analyzes the scope of group number analysis and is freely specified by artificial different " stability analysis group numbers "; Here " scope " can be the zone; Also can be electric pressure) can corresponding different criterion group number, each " stability analysis group number " also can corresponding many group criterions, have special criterion that information is set and supply to call; The criterion kind can continue to add according to actual needs, and is as shown in Figure 3.

The current criterion of considering has:

A. maximum generation machine merit angular difference, maximum generation machine merit angular difference surpasses this value and then thinks system's unstability in the system.

B. the minimum busbar voltage duration, when minimum busbar voltage in the system is lower than set point and surpass the duration, think system's unstability.

C. the minimum generator frequency duration, when minimum generator frequency in the system is lower than set point and surpass the duration, think system's unstability.

D. circuit overload (thermally-stabilised constraint), given line specifies meritorious constantly absolute value greater than specifying numerical value promptly to think system's unstability after fault in the system.

E. whether merit angle swing curve vibration calms down, i.e. the merit angle swing curve vibration of two generators is dispersed or died away, if disperse then think underdamping, system's unstability.

F. whether line power fluctuation calms down, when the power fluctuation of current through line is thought system's unstability during greater than a certain index.

G. other criterions.Whether excise like circuit, promptly voltage or frequency etc. are lower than certain circuit of a certain limit value excision and promptly think system's unstability.

(5) surely controlling strategy asks for

In the actual electric network, can be through steady control strategy the raising stability limit is set.After the forecast failure collection check system unstability; Ask for steady control policing feature if started; To implement steady control strategy successively according to the order that is provided with of steady control strategy; Try to achieve steady control strategy and implement the corresponding stability limit of back target section, thus try to achieve indirectly improve the maximum ability to transmit electricity of transmission cross-section the steady control means that will take.Steady control strategy commonly used has: cutter, cutting load, tangent line road, low-frequency low-voltage load shedding etc.Fig. 2 has provided the method flow of asking for steady control strategy.

The invention has the beneficial effects as follows: according to the daily calculation stability limit of power system operating mode personnel and ask for the process establishment corresponding strategy of steady control strategy; Transient mode adjustment, trend calculating, the current transmit power calculation of transmission cross-section, reactive power compensation calculating, fault verification, stabilize decision have been realized that through the method for asking for the large-scale interconnected power system transmission of electricity limit and steady control strategy automatically fast automation completely calculates; Thereby can substitute artificial calculating transmission cross-section stability limit fully and ask for the tactful process of steady control, especially when the transmission of electricity limit of the catenet of asking for poor astringency, have significant advantage.

Claims (3)

1. A method for automatically and quickly obtaining the stability limit and stability control strategy of a large-scale interconnected power grid, the main steps including automatic adjustment of transition mode, power flow calculation, automatic switching of shunt capacitor reactance, fault verification; its characteristics are: a. Determine the adjustment amount according to the current transmission limit value of the main transmission section and its estimated limit value, and update the active and reactive power of the generators and loads participating in the power flow adjustment; b. Conventional power flow calculation, if not converged, go to step c; if converged, go to step e; c. Recalculate the power flow with the previous converged power flow result as the initial value. If it still does not converge, go back to the last stable operation point, reduce the step size and return to a; if it converges, go to step d; d. Check the expected fault set. If the system is unstable and the stability control strategy is not considered, return to the last stable operation point, reduce the step size and return to a; if the system is unstable and the stability control strategy needs to be considered, proceed in order After starting the stability control strategy, re-check the fault. If the system is unstable, reduce the step size and return to a; if the system is stable, enter step e; e. Judging whether the transmission power of the current target section reaches the estimated limit value or the adjustment step size has reached the adjustment accuracy, as long as one of the two is satisfied, the result is output, and the calculation is stopped; otherwise, enter step f; f. If there is no instability or the power flow does not converge completely during the aforementioned adjustments, maintain the original step size, increase the transmission power of the designated transmission section based on the current stable operating point of the power flow, and return to step a; otherwise, run stably at the current power flow Based on the point, reduce the step size, increase the transmission power of the specified transmission section, and return to step a. 2. The method for automatically and rapidly obtaining the stability limit and the stability control strategy of a large-scale interconnected power grid according to claim 1 is characterized in that: if the power flow calculation of the straight start in the transition mode adjustment process does not converge, then the previous converged The result of the power flow is used as the initial value to calculate the power flow again; after each power flow calculation is completed, the parallel capacitive reactance is automatically switched on and off according to the preset input and exit voltages; different severe levels of stability judgments are adopted for power grids with different partitions or different voltage levels According to the data, the comprehensive damping is fully considered; the stability control strategies are put into operation in sequence, and the main stability control strategies considered are machine cutting, load shedding, line cutting, oscillation splitting, and low-frequency and low-voltage load shedding. 3. The method for automatically and quickly obtaining the stability limit and stability control strategy of large-scale interconnected power grid according to claim 1, characterized in that: the influence of the series transmission section of the main transmission section on its transmission limit is fully considered, if its serial The section has reached the thermal stability limit, and the transmission limit of the main transmission section will be restricted accordingly.

Images