CN104113056B - A kind of optimization method of current limiting low-voltage controling parameters - Google Patents

Abstract

The invention discloses a kind of current limiting low-voltage Optimization about control parameter method, the method devises a kind ofly takes into account the meritorious transmission characteristic of current conversion station and the optimization object function of reactive power consumption characteristic, chooses ceiling voltage threshold value VD_H, the minimum voltage threshold value VD_L of current limiting low-voltage module and minimum current limit value ID_L as optimized variable; Utilize the custom feature of electro-magnetic transient time-domain-simulation software to be embedded in simulated program by optimization object function and optimization method, realize the effectively optimizing of current limiting low-voltage parameter.

Description

A kind of optimization method of current limiting low-voltage controling parameters

Technical field

The present invention relates to a kind of optimization method of HVDC (High Voltage Direct Current) transmission system current limiting low-voltage controling parameters, belong to electric power system control running protection technical field.

Background technology

The current limiting low-voltage of HVDC (High Voltage Direct Current) transmission system controls to refer to and to limit direct current when exchanging commutation voltage or direct voltage is reduced to certain value, by restriction direct current, suppress converter to the demand of reactive power consumption on the one hand, increase Advanced firing angle β on the other hand thus increase extinguish angle γ, reducing with this possibility that follow-up commutation failure occurs.Although converter can be reduced to idle demand by force if cross for the restriction of direct current, converter will be hindered active power transfer resume speed.Experts and scholars often only studied how reducing in converter reactive requirement or direct current transmission recovery characteristics in the past, did not propose reliable research method from the two qualitative optimizations in aspect.How to solve converter reactive power consumption and meritorious transmission coordination optimization problem does not carry out rising up into research.This patent proposes in ac and dc systems fault and can significantly reduce Inverter Station between convalescence to the reactive requirement of AC system and meritorious fast quick-recovery proposition Mathematical Modeling quantization scheme in converter current limiting low-voltage controlling unit, remain the characteristic that typical low pressure Current limited Control can stablize alternating voltage simultaneously, be conducive to the possibility reducing follow-up commutation failure.

Current limiting low-voltage control characteristic is mainly by four parameter (ID_L, ID_H, VD_L, VD_H) impacts, and its setting value is determined according to operation characteristic under a series of disturbance and low pressure.Under the system failure is run, the parameter of current limiting low-voltage device is to voltage, the meritorious transmission of power-angle stability, reactive requirement and flow to very crucial.Usual ID_H values constant is 1.0, therefore can comprise ID_L, VD_L and VD_H tri-for the parameter optimized.Compared with the transformation to alternating current-direct current primary system, only need pay very little cost to the optimization of current limiting low-voltage parameter and can produce good effect to the recovery of direct current system.But the optimization means of current limiting low-voltage parameter is limited to the method trying to gather more at present, depend on engineering experience, efficiency is lower, and classical current limiting low-voltage control characteristic broken line is as changed in Fig. 3 shown in front curve.

Summary of the invention

For overcoming the deficiencies in the prior art, the present invention proposes a kind of parameter intelligent optimization method for HVDC (High Voltage Direct Current) transmission system mesolow Current limited Control; After its object is to solve DC transmission system fault, converter suppresses reactive requirement and accelerates the coordination optimization problem between meritorious recovery; Optimize current limiting low-voltage controling parameters, intelligent search optimized operation point, makes consumed idle peak value little as far as possible, and meritorious transmission simultaneously recovers fast as far as possible, improves the runnability in direct current system transient process.

The technical scheme that the present invention takes is:

An optimization method for current limiting low-voltage controling parameters, it comprises the following steps:

Step 1, set up and take into account direct current and to gain merit the optimization object function of restorability and converter reactive power consumption size, described optimization object function is:

minf(x)＝(ω _pΔE _loss+ω _qΔQ _peak)(1)

Wherein: the minimum value that minf (x) is optimization object function, Δ E _loss, Δ Q _peakbe respectively direct current to gain merit restorability and converter reactive power consumption size, ω _pand ω _qbe respectively Δ E _loss, Δ Q _peakweights, and ω _p+ ω _q=1.0;

Step 2, determine the controling parameters of optimizable current limiting low-voltage, described controling parameters comprises ceiling voltage threshold value VD_H, minimum voltage threshold value VD_L and minimum current limit value ID_L tri-variablees, and the number range according to described three variablees forms optimizing feasible zone;

Step 3, by electro-magnetic transient time-domain simulation program embed optimized algorithm, obtain the optimum current limiting low-voltage controling parameters in described optimizing feasible zone;

Step 4, by electromagnetic transient simulation contrast current limiting low-voltage controling parameters initial value and optimal control parameter under dynamic response, checking optimum results feasibility;

Wherein: described step 3 comprises:

Step 31, utilize electromagnetic transients program to set up the computation model of optimization object function and optimized algorithm, and carry out initialization;

Step 32, provided one group of given controling parameters of current limiting low-voltage by described computation model, according to described given controling parameters, the electromagnetic transient simulation carrying out electric network calculates, and obtains initial optimization target function value f ₁;

Step 33, employing optimized algorithm successively produce new controling parameters, again carry out electromagnetic transient simulation calculating, obtain optimization object function calculated value f _j, when:

$\left\{\begin{array}{c}|f_j-f_{-1}|\&le;\mathrm{\&epsiv;}\\ f_j<\min \left\{f_i\right\}\\ i\&Element;(0,j),i\&Element;Z\end{array}\right.---\left(2\right)$

Time, then think and calculate convergence, this optimization object function calculated value f _jcorresponding controling parameters is optimal control parameter, otherwise, perform step 34;

Step 34, judge optimize number of times whether reach maximum simulation times, if so, then choose optimization object function calculated value f _jwith initial optimization target function value f ₁in a minimum corresponding controling parameters as optimal control parameter, otherwise, continue to perform step 33.

Δ E in described step 1 _losscomputational methods be:

$\left\{\begin{array}{c}{\mathrm{\&Delta;E}}_{\mathrm{loss}}=E_{\mathrm{loss}}/E_{\mathrm{loss}0}-1.0\\ E_{\mathrm{loss}}={\&Integral;}_{t0}^{t1}(P_s-P\left(t\right))\mathrm{dt}\\ E_{\mathrm{loss}0}={\&Integral;}_{t0}^{t1}(P_s-P_0\left(t\right))\mathrm{dt}\end{array}\right.---\left(3\right)$

Wherein, P _sfor the active power of direct current conveying under steady state situations, P ₀be respectively under same fault condition with P, direct current system adopts current limiting low-voltage controling parameters initial value and optimal control parameter to calculate the active power of gained separately, and t0 is the fault clearance moment, and t1 is that direct current active power returns to P _s90% moment.

Described Δ Q _peakcomputational methods be:

ΔQ _peak＝Q _peak/Q _peak0-1.0(4)

Wherein, Q _peak0and Q _peakbe respectively under same fault condition, the maximum idle numerical value that between the convalescence that direct current system adopts current limiting low-voltage controling parameters initial value and optimal control parameter to calculate gained separately, inverter consumes.

Described current limiting low-voltage controling parameters initial value is current limiting low-voltage controling parameters value when not being optimized.

According to engineering experience, the number range of described three variablees is limited:

$\left\{\begin{array}{c}0.4\&le;\mathrm{VD}\_H\&le;0.9\\ 0.1\&le;\mathrm{VD}\_L\&le;0.6\\ 0.2\&le;\mathrm{ID}\_L\&le;0.5\\ \mathrm{VD}\_H\&GreaterEqual;\mathrm{VD}\_L\end{array}\right.---\left(5\right).$

Described dynamic response comprises the active power of inverter transmission and the reactive power of consumption.

Described optimized algorithm is genetic algorithm.

The present invention compared with prior art, its beneficial effect is: it sets up the computation model of optimization object function and optimized algorithm by electromagnetic transients program, and minimum optimization object function is obtained in optimizing feasible zone, to optimize current limiting low-voltage controling parameters, intelligent search optimized operation point, make consumed idle peak value little as far as possible, meritorious transmission simultaneously recovers fast as far as possible, improves the runnability in direct current system transient process.

Accompanying drawing explanation

Fig. 1 is the electromagnetic transient simulation result figure of the active power of inverter transmission and the dynamic response of reactive power before and after current limiting low-voltage parameter optimization of consumption;

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

Fig. 3 is certain ± 800KV extra-high voltage direct-current control system current limiting low-voltage optimize before and after characteristic fold line comparison diagram.

Embodiment

Below in conjunction with the drawings and specific embodiments, content of the present invention is described in further details.

Embodiment

A kind of current limiting low-voltage Optimization about control parameter method, it comprises the following steps:

The optimization aim of step 1, design one reflection DC system fault restorability.This index is taken into account direct current and to be gained merit resume speed and converter reactive power consumption size.

Step 2, determine the controling parameters of optimizable current limiting low-voltage to comprise ceiling voltage threshold value VD_H, minimum voltage threshold value VD_L and minimum current limit value ID_L tri-variablees, form optimizing feasible zone.

Step 3, design a kind of intelligent optimization method being adapted to electro-magnetic transient time-domain simulation program, the optimum current limiting low-voltage controling parameters that user can be obtained under set objective by working procedure.

Step 4, by electromagnetic transient simulation contrast optimize before and after result, checking optimum results feasibility.If there is unreasonable result, then need to return step 2 and revise optimizing feasible zone.

Optimization aim in step 1 has taken into account the reactive power consumption of recovery that direct current gains merit and converter, which includes the quantitative indices describing meritorious restorability and converter reactive power consumption.

Step 11, to design optimization object function as follows:

Minf (x)=(ω _pΔ E _loss+ ω _qΔ Q _peak) (6) wherein, Δ E _loss, Δ Q _peakas shown in formula (7), (8), ω _eand ω _qΔ E respectively _losswith Δ Q _peakweights, ω _e+ ω _q=1.0.

Step 12, employing index Δ E _lossportray direct current to gain merit restorability:

$\left\{\begin{array}{c}{\mathrm{\&Delta;E}}_{\mathrm{loss}}=E_{\mathrm{loss}}/E_{\mathrm{loss}0}-1.0\\ E_{\mathrm{loss}}={\&Integral;}_{t0}^{t1}(P_s-P\left(t\right))\mathrm{dt}\\ E_{\mathrm{loss}0}={\&Integral;}_{t0}^{t1}(P_s-P_0\left(t\right))\mathrm{dt}\end{array}\right.---\left(7\right)$

Wherein, P _sfor the active power of direct current conveying under steady state situations, P ₀be respectively under same fault condition with P, direct current system adopts current limiting low-voltage controling parameters initial value and the numerical value after optimizing to calculate the active power of gained separately, and t0 is the fault clearance moment, and t1 is that direct current active power returns to P _s90% moment.

Step 13, employing portray Δ Q _peakthe size of converter reactive power consumption:

ΔQ _peak＝Q _peak/Q _peak0-1.0(8)

Wherein, Q _peak0and Q _peakbe respectively under same fault condition, the maximum idle numerical value that between the convalescence that direct current system adopts current limiting low-voltage controling parameters initial value and the numerical value after optimizing to calculate gained separately, inverter consumes.

Optimizing feasible zone in step 2 is defined by ceiling voltage threshold value VD_H, the minimum voltage threshold value VD_L of current limiting low-voltage and minimum current limit value ID_L tri-parameters, and the number range of these three parameters limits as follows according to engineering experience:

$\left\{\begin{array}{c}0.4\&le;\mathrm{VD}\_H\&le;0.9\\ 0.1\&le;\mathrm{VD}\_L\&le;0.6\\ 0.2\&le;\mathrm{ID}\_L\&le;0.5\\ \mathrm{VD}\_H\&GreaterEqual;\mathrm{VDL}\end{array}\right.---\left(9\right)$

In electro-magnetic transient time-domain simulation program, embed optimized algorithm in step 3, please refer to shown in Fig. 2, it specifically comprises:

Step 31, utilize " User Defined " function of electromagnetic transients program (such as PSCAD/EMTDC) to set up the computation model of target function and related optimization (as genetic algorithm), and carry out initialization;

Step 32, provided one group of controling parameters of current limiting low-voltage by the computation model in step 31, its primary data optimized as current limiting low-voltage, according to this primary data, the electromagnetic transient simulation carrying out electric network calculates;

Step 33, according to step 32 electromagnetic transient simulation result calculating target function numerical value, and with last comparison of computational results, judge such as formula (10), if the absolute value of the difference of the two is less than setting constant ε, and current iteration calculated value f _jbe less than f _i(wherein, and i ∈ (0, j); i is integer), then think and calculate convergence, last group controling parameters is optimized parameter and shuts down; otherwise (also comprising last result of calculation not exist and situation about cannot compare), enter step 34.

$\left\{\begin{array}{c}|f_j-f_{j-1}|\&le;\mathrm{\&epsiv;}\\ f_j<\min \left\{f_i\right\}\\ i\&Element;(0,j),i\&Element;Z\end{array}\right.---\left(10\right)$

Step 34, judge whether arrive setting maximum simulation times.If so, then choose one group of minimum current limiting low-voltage parameter of target function f (x) as optimized parameter and shut down; If not, then the optimization method in invocation step 31 continues to find next group current limiting low-voltage controling parameters, and returns step 32.

Step 4 verifies the feasibility of optimum results.

By the following examples further supplementary notes are done to the present invention:

Choose PSCAD/EMTDC as electro-magnetic transient time-domain-simulation platform, according to step 1 ~ step 3 of the present invention, to certain ± 800KV extra-high voltage direct-current control system current limiting low-voltage VD_H, VD_L and ID_L tri-parameters are optimized, and selected ω _p=ω _q=0.5.The target function numerical value of three parameters and correspondence that gained optimizes front and back is as following table:

Table 1 optimizes three parameters of front and back and the target function numerical value of correspondence

According to step 4 of the present invention, inverter side change of current bus arranges three phase short circuit fault, and earth resistance is 8 Ω, and the duration is 100ms, the active power of simulation comparison inverter transmission and the dynamic response of reactive power before and after current limiting low-voltage parameter optimization of consumption, as shown in Figure 1.

Although the present invention is described by specific embodiment, it will be appreciated by those skilled in the art that, without departing from the present invention, various conversion can also be carried out and be equal to substituting to the present invention.In addition, for particular condition or application, various amendment can be made to the present invention, and not depart from the scope of the present invention.Therefore, the present invention is not limited to disclosed specific embodiment, and should comprise the whole execution modes fallen within the scope of the claims in the present invention.

Claims (5)

1. an optimization method for current limiting low-voltage controling parameters, is characterized in that, it comprises the following steps:

Step 1, set up and take into account direct current and to gain merit the optimization object function of restorability and converter reactive power consumption size, described optimization object function is:

minf(x)＝(ω _p△E _loss+ω _q△Q _peak)(1)

Wherein: the minimum value that minf (x) is optimization object function, △ E _loss, △ Q _peakbe respectively direct current to gain merit restorability and converter reactive power consumption size, ω _pand ω _qbe respectively △ E _loss, △ Q _peakweights, and ω _p+ ω _q=1.0;

△ E in described step 1 _losscomputational methods be:

${\mathrm{\&Delta;E}}_{loss}=\frac{{\&Integral;}_{t0}^{t1}(P_s-P(t\left)\right)dt}{{\&Integral;}_{t0}^{t1}(P_s-P_0(t\left)\right)dt}-1.0---\left(3\right)$

Wherein, P _sfor the active power of direct current conveying under steady state situations, P ₀be respectively under same fault condition with P, direct current system adopts current limiting low-voltage controling parameters initial value and optimal control parameter to calculate the active power of gained separately, and t0 is the fault clearance moment, and t1 is that direct current active power returns to P _s90% moment;

Described △ Q _peakcomputational methods be:

△Q _peak＝Q _peak/Q _peak0-1.0(4)

Wherein, Q _peak0and Q _peakbe respectively under same fault condition, the maximum idle numerical value that between the convalescence that direct current system adopts current limiting low-voltage controling parameters initial value and optimal control parameter to calculate gained separately, inverter consumes;

Step 2, determine the controling parameters of optimizable current limiting low-voltage, described controling parameters comprises ceiling voltage threshold value VD_H, minimum voltage threshold value VD_L and minimum current limit value ID_L tri-variablees, and the number range according to described three variablees forms optimizing feasible zone;

Step 3, by electro-magnetic transient time-domain simulation program embed optimized algorithm, obtain the optimum current limiting low-voltage controling parameters in described optimizing feasible zone;

Step 4, by electromagnetic transient simulation contrast current limiting low-voltage controling parameters initial value and optimal control parameter under dynamic response, checking optimum results feasibility;

Wherein: described step 3 comprises:

Step 31, utilize electromagnetic transients program to set up the computation model of optimization object function and optimized algorithm, and carry out initialization;

Step 32, provided one group of given controling parameters of current limiting low-voltage by described computation model, according to described given controling parameters, the electromagnetic transient simulation carrying out electric network calculates, and obtains initial optimization target function value f ₁;

Step 33, employing optimized algorithm successively produce new controling parameters, again carry out electromagnetic transient simulation calculating, obtain optimization object function calculated value f _j, when:

$\left\{\begin{array}{c}|f_j-f_{j-1}|\&le;\mathrm{\&epsiv;}\\ f_j<min\left\{f_i\right\}\\ i\&Element;(0,j),i\&Element;Z\end{array}\right.---\left(2\right)$

Time, then think and calculate convergence, this optimization object function calculated value f _jcorresponding controling parameters is optimal control parameter, otherwise, perform step 34;

Step 34, judge optimize number of times whether reach maximum simulation times, if so, then choose optimization object function calculated value f _jwith initial optimization target function value f ₁in a minimum corresponding controling parameters as optimal control parameter, otherwise, continue to perform step 33.

2. the optimization method of current limiting low-voltage controling parameters according to claim 1, is characterized in that, described current limiting low-voltage controling parameters initial value is current limiting low-voltage controling parameters value when not being optimized.

3. the optimization method of current limiting low-voltage controling parameters according to claim 1, is characterized in that, according to engineering experience, limits the number range of described three variablees:

$\left\{\begin{array}{c}0.4\&le;VD\_H\&le;0.9\\ 0.1\&le;VD\_L\&le;0.6\\ 0.2\&le;ID\_L\&le;0.5\\ VD\_H\&GreaterEqual;VD\_L\end{array}\right.---\left(5\right).$

4. the optimization method of current limiting low-voltage controling parameters according to claim 1, is characterized in that, described dynamic response comprises the active power of inverter transmission and the reactive power of consumption.

5. the optimization method of current limiting low-voltage controling parameters according to claim 1, is characterized in that, described optimized algorithm is genetic algorithm.