CN103078311A - Direct current predicting and setting method for inhibiting commutation failure - Google Patents

Abstract

The invention discloses a direct current predicting and setting method for inhibiting commutation failure. Aiming at the commutation failure problem of an inverter of a direct current power transmission system, the direct current predicting and setting method is effectively established by detecting the direct current at the inverse side of the direct current power transmission system and the alternating current bus voltage, comprehensively considering the influence of the direct current and the alternating current bus voltage on the commutation process of the inverter, and utilizing alternating current bus voltage zero-sequence voltage component, abc-alpha beta conversion and alternating voltage valid values. The method provided by the invention can be used for laying a good foundation for further researching the predicting control method for commutation failure of a direct current power transmission system.

Description

A kind of direct current prediction setting method that suppresses commutation failure

Technical field

The invention belongs to power system operation and control technology field, be specifically related to a kind of direct current prediction setting method that suppresses commutation failure.

Background technology

Direct current transportation has that transmission capacity is large, loss is little, the power adjustments advantages such as flexible, asynchronous contact ability is strong rapidly, and the aspects such as it is interconnected at large regional power grid, long-distance and large-capacity power transmission are widely used.Along with the continuous lifting of China's power grid construction level, DC transmission engineering has become the important technical of optimizing the power network resources configuration, coordinating Regional Economic Development.Commutation failure can cause that direct voltage decline and direct current increase in short-term etc. as canonical system fault common in the HVDC (High Voltage Direct Current) transmission system; Continuous commutation failure easily causes the operation of direct current system derate, even causes the locking of valve group or utmost point locking, is unfavorable for system's operation.Commutation failure mainly betides in the inverter in the DC transmission system, and existing commutation failure Prediction and Control Technology reduces its occurrence probability with the setting value that increases gating advance angle β or pass angle of rupture γ.

According to the trigger delay angular region constraint that works in the inverting converter, if when commutation voltage descends comparatively seriously, maximum trigger delay angle also may be difficult to guarantee in advance inverter success commutation; In addition, more angle of overlap increases, and also may make to close the angle of rupture and be subject to next commutation failure process influence and diminish, and causes commutation failure, only increases angle of overlap μ and suppresses Commutation Failure its inherent limitation is arranged by reducing trigger delay angle α.

Summary of the invention

Goal of the invention: for the inherent limitation of above-mentioned existing Commutation Failure Prediction and Control Technology, the purpose of this invention is to provide a kind of direct current prediction setting method that suppresses commutation failure.

Technical scheme: for achieving the above object, the technical solution used in the present invention is a kind of direct current prediction setting method that suppresses commutation failure, comprises the steps:

(1) supplemental characteristic initialization, described supplemental characteristic comprises: commutation failure zero sequence voltage component Product-factor k _{Z_DIFF_LEVEL}And α/β translation difference long-pending factor K on duty _{AB_DIFF_LEVEL}

(2) input inversion side direct current I _{D_inv}, ac bus three-phase instantaneous voltage u _a, u _b, u _cAnd voltage effective value V _{AC_inv}, be perunit value, and input simultaneously commutation failure residual voltage V _{Z_DIFF_LEVEL}And α/β transform component set point V _{AB_DIFF_LEVEL}

(3) respectively to I _{D_inv}And V _{AC_inv}Carry out 2s filtering, obtain 2s filter value I _{D_inv_2s}Filter value and

V _{AC_inv_2s}Filter value, and do following calculating;

α/β conversion and calculating:

$u_{\mathrm{\α}}=(u_b-u_c)/\sqrt{3},u_{\mathrm{\β}}=({2u}_a-u_b-u_c)/3,U_{\mathrm{\α\β}}=\sqrt{u_{\mathrm{\α}}^2+u_{\mathrm{\β}}^2}$

Zero-sequence component is calculated:

U _Z=|u _a+u _b+u _C|

(4) to U _{α β}Carry out 2s filtering, obtain U _{α β _ 2s}Filter value calculates (U _{α β _ 2s}Filter value-U _{α β}) and make itself and U _ZMaximum keep 20ms, be designated as respectively U _{AB_DIFF_MAXHOLD}And U _{Z_DIFF_MAXHOLD}

(5) judge U _ZWhether more than or equal to V _{Z_DIFF_LEVEL}If,, calculate D _z=k _{Z_DIFF_LEVEL}U _{Z_DIFF_MAXHOLD}, otherwise D _z=0;

(6) judge (

-U _{α β}) whether more than or equal to V _{AB_DIFF_LEVEL}If,, calculate D _{α β}=K _{AB_DIFF_LEVEL}U _{AB_DIFF_MAXHOLD}, otherwise D _{α β}=0;

(7) calculate:

D=max{D _Z，D _αβ}

$V_Z=1-U_{Z\_\mathrm{DIFF}\_\mathrm{MAXHOLD}}/\sqrt{2}$

K=min{V _{AC_inv}, V _{α β}, V _Z}/V _{AC_inv_2s}Filter value

(8) whether judge D greater than zero, if, the direct current prediction setting value I when then calculating commutation failure _{D_PREV}=2kI _{D_inv_2s}Filter value-I _{D_inv}, otherwise I _{D_PREV}Prediction when not doing commutation failure is adjusted, and it is normal direct current setting value I _{D_NOR}

(9) output I _{D_PREV}

Beneficial effect: according to the analysis of commutation failure mechanism, when the system failure causes direct current increase, the decline of AC system busbar voltage, the direct current PREDICTIVE CONTROL that holds water then can strengthen control system to the control of commutation process, to satisfy the necessary condition of inverter success commutation under the fault condition as far as possible, reduce its commutation failure occurrence probability.At present, the direct current that suppresses commutation failure predicts that setting method there is not yet bibliographical information.The direct current prediction setting method of the inhibition commutation failure that the present invention proposes, on the basis of existing commutation failure forecast Control Algorithm, utilize the detection of inversion side direct current, ac bus zero sequence voltage component, abc-α β conversion and ac bus voltage effective value, set up the direct current prediction setting method that can be used for reducing Commutation Failure probability in the fault in ac transmission system situation, for the PREDICTIVE CONTROL Study on Measures of DC transmission system commutation failure is laid a good foundation.The present invention has following advantage, and the direct current prediction setting method that proposes on the one hand is to only by reducing the trigger delay angle, increasing the commutation failure PREDICTIVE CONTROL module that angle of overlap suppresses Commutation Failure and further replenish perfect; On the other hand, the basis of practicable commutation failure PREDICTIVE CONTROL module give perfect in, point out that further direct current is controlled this research direction on the commutation failure predictive control strategy.

Description of drawings

Fig. 1 is the inventive method flow chart;

Fig. 2 is that the commutation failure direct current is predicted the module frame chart of adjusting.

Embodiment

Below in conjunction with the drawings and specific embodiments, further illustrate the present invention, should understand these embodiment only is used for explanation the present invention and is not used in and limits the scope of the invention, after having read the present invention, those skilled in the art all fall within the application's claims limited range to the modification of the various equivalent form of values of the present invention.

Be elaborated below in conjunction with the technical scheme of accompanying drawing to invention:

The safe and stable operation of DC transmission system in DC transmission system commutation failure (being mainly Commutation Failure) serious threat, to its Prediction and Control Technology also existing many-sided research, commutation failure PREDICTIVE CONTROL module has solved preferably and has increased the contradiction that angle of overlap suppresses commutation failure and systematic economy operation, its basic thought is: when detecting fault in ac transmission system and may cause commutation failure, in inversion side trigger delay angle, deduct certain angle, realize triggering in advance.Yet according to Related literature analysis as can be known, only by reducing the trigger delay angle, increasing angle of overlap and suppress Commutation Failure its inherent limitation is arranged.According to the further analysis of commutation failure mechanism, the direct current PREDICTIVE CONTROL that holds water then can strengthen control system to the control of commutation process, to satisfy the necessary condition of inverter success commutation under the fault condition as far as possible, reduces its commutation failure occurrence probability.

The inventive method as shown in Figure 1, according to the different faults type of inversion top-cross streaming system (symmetrical and asymmetric), conversion is detected with ac bus voltage zero sequence voltage with based on α bC-α β respectively; And compare to determine whether respectively to cause Commutation Failure with set point, start the direct current PREDICTIVE CONTROL.The commutation failure PREDICTIVE CONTROL module direct current that the present invention relates to predicted value of adjusting is got following form:

I _{D_PREV}=2kI _{D_inv_2s}Filter value-I _{D_inv}

In the formula, I _{D_inv}Be inversion side direct current, I _{D_inv_2s}Filter value is its 2s filter value; Proportionality coefficient k=min{V _{AC_inv}, V α _β, V _Z}/V _{AC_inv_2s}Filter value, V _{AC_inv}Perunit value for inversion top-cross streaming system busbar voltage effective value;

U _{AB_DIFF_MAXHOLD}(U for abc-α β conversion _{α β _ 2s}Filter value-U _{α β}) maximum 20ms retention value;

$V_Z=1-U_{Z\_\mathrm{DIFF}\_\mathrm{MAXHOLD}}/\sqrt{2},U_{Z\_\mathrm{DIFF}\_\mathrm{MAXHOLD}}$ Be zero sequence voltage component absolute value U _ZMaximum 20ms retention value.

Fig. 2 is the commutation failure direct current prediction that the present invention relates to module frame chart of adjusting, with ac bus voltage zero sequence voltage component detection AC system unbalanced fault, based on abc-α β change detection symmetric fault: zero sequence voltage component U _Z=| u _a+ u _D+ u _c|, α/β conversion $u_{\mathrm{\α}}=(u_b-u_c)/\sqrt{3},u_{\mathrm{\β}}=$ $(2u_a-u_b-u_c)/3,$ Calculate $U_{\mathrm{\α\β}}=\sqrt{u_{\mathrm{\α}}^2+u_{\mathrm{\β}}^2};$

To U _{α β}Carry out 2s filtering, obtain U _{α β _ 2s}Filter value calculates (U _{α β _ 2s filter value}-U _{α β}) and make itself and U _ZMaximum keep 20ms, be designated as respectively U _{Z_DIFF_MAXHOLD}And U _{AB_DIFF_MAXHOLD}

Z_DIFF_LEVEL and AB_DIFF_LEVEL respectively in order to judge AC system asymmetric with the symmetric fault situation under, inverter possibility generation commutation failure, and judge that signal is continued 20ms.

Z_DIFF_GAIN and AB_DIFF_GAIN are U _{Z_DIFF_MAXHOLD}With U _{AB_DIFF_MAXHOLD}The non-zero weights, when module is judged the product output of selecting corresponding component and weights when may commutation failure occur, otherwise export zero setting; The output of the two is got higher value in order to judge whether that needing to start direct current prediction setting value is controlled, if then calculate commutation failure direct current prediction setting value I _{D_PREV}=2kI _{D_inv_2s}Filter value-I _{D_inv}, otherwise I _{D_PREV}Do not do the commutation failure prediction and adjust, it is normal direct current setting value I _{D_NOR}I _{D_PREV}Export direct current transportation utmost point key-course control system to, in order to suppress Commutation Failure.

Claims (1)

1. a direct current prediction setting method that suppresses commutation failure is characterized in that comprising the steps:

(1) supplemental characteristic initialization, described supplemental characteristic comprises: commutation failure zero sequence voltage component Product-factor k _{Z_DIFF_LEVEL}And α/β translation difference long-pending factor k on duty _{AB_DIFF_LEVEL}

(2) input inversion side direct current I _{D_inv}, ac bus three-phase instantaneous voltage u _a, u _b, u _cAnd voltage effective value V _{AC_inv}, be perunit value, and input simultaneously commutation failure residual voltage V _{Z_DIFF_LEVEL}And α/β transform component set point V _{AB_DIFF_LEVEL}

(3) respectively to I _{D_inv}And V _{AC_inv}Carry out 2s filtering, obtain 2s filter value I _{D_inv_2s}Filter value and V _{The AC_inv_2s filter value}, and do following calculating;

α/β conversion and calculating:

$u_{\mathrm{\α}}=(u_b-u_c)/\sqrt{3},$ u _β＝(2u _a-u _b-u _c)/3， $U_{\mathrm{\α\β}}=\sqrt{u_{\mathrm{\α}}^2+u_{\mathrm{\β}}^2}$

Zero-sequence component is calculated:

U _Z＝|u _a+u _b+u _c|

(4) to U _{α β}Carry out 2s filtering, obtain U _{α β _ 2s filter value}, calculate (U _{α β _ 2s filter value}-U _{α β}) and make itself and U _ZMaximum keep 20ms, be designated as respectively U _{AB_DIFF_MAXHOLD}And U _{Z_DIFF_MAXHOLD}

(5) judge U _ZWhether more than or equal to V _{Z_DIFF_LEVEL}If,, calculate D _z=k _{Z_DIFF_LEVEL}U _{Z_DIFF_MAXHOLD}, otherwise D _Z=0;

(6) judge

Whether more than or equal to V _{AB_DIFF_LEVEL}If,, calculate D _{α β}=k _{AB_DIFF_LEVEL}U _{AB_DIFF_MAXHOLD}, otherwise D _{α β}=0;

(7) calculate:

D＝max{D _z，D _αβ}

$V_Z=1-U_{Z\_\mathrm{DIFF}\_\mathrm{MAXHOLD}}/\sqrt{2}$

K=min{V _{AC_inv}, V _{α β}, V _Z}/V _{The AC_inv_2s filter value}

(8) whether judge D greater than zero, if, the direct current prediction setting value I when then calculating commutation failure _{D_PREV}=2kI _{The d_inv_2s filter value}-I _{D_inv}, otherwise I _{D_PREV}Prediction when not doing commutation failure is adjusted, and it is normal direct current setting value I _{D_NOR}

(9) output I _{D_PREV}

Images