CN103078311B - 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 suppressing 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 suppressing commutation failure.

Background technology

Direct current transportation has the advantages such as transmission capacity is large, loss is little, power adjustments rapid flexible, asynchronous contact ability are strong, makes it be widely used in large regions Power System Interconnection, long-distance and large-capacity power transmission etc.Along with the continuous lifting of China's power grid construction level, DC transmission engineering has become the important technical optimized power network resources configuration, coordinate Regional Economic Development.Commutation failure, as canonical system fault common in HVDC (High Voltage Direct Current) transmission system, can cause direct voltage decline and direct current to increase in short-term; Continuous print commutation failure easily causes direct current system derate to run, and even causes the locking of valve group or pole locking, is unfavorable for system cloud gray model.In DC transmission system, commutation failure mainly betides in inverter, and existing commutation failure Prediction and Control Technology reduces its occurrence probability with the setting value increasing gating advance angle β or pass angle of rupture γ.

According to the trigger delay angle range constraint working in inverting converter, if when commutation voltage declines comparatively serious, maximum trigger delay angle also may be difficult to ensure inverter success commutation in advance; In addition, more angle of overlap increases, and the pass angle of rupture also may be made to be subject to next commutation failure process influence and to diminish, cause commutation failure, increases angle of overlap μ suppress Commutation Failure to have its inherent limitation by means of only reduction 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 object of this invention is to provide a kind of direct current prediction setting method suppressing 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 suppressing 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}with α/β conversion difference Product-factor K _{aB_DIFF_LEVEL};

(2) inverter side direct current I is inputted _{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 commutation failure residual voltage V simultaneously _{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 calculates:

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 U respectively _{aB_DIFF_MAXHOLD}and U _{z_DIFF_MAXHOLD};

(5) U is judged _zwhether be more than or equal to V _{z_DIFF_LEVEL}, if so, calculate D _z=k _{z_DIFF_LEVEL}u _{z_DIFF_MAXHOLD}, otherwise D _z=0;

(6) judge ( -U _{α β}) whether be more than or equal to V _{aB_DIFF_LEVEL}, if so, 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) judge whether D is greater than zero, if so, then calculate direct current prediction setting value I during 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 DC setting value I _{d_NOR};

(9) I is exported _{d_PREV}.

Beneficial effect: according to the analysis of commutation failure mechanism, when the system failure causes direct current increase, AC system busbar voltage declines, the direct current PREDICTIVE CONTROL held water then can strengthen the control of control system to commutation process, to meet the necessary condition of inverter success commutation under fault condition as far as possible, reduce its commutation failure occurrence probability.At present, the direct current of commutation failure prediction setting method is suppressed to there is not yet bibliographical information.The direct current prediction setting method of the suppression commutation failure that the present invention proposes, on the basis of existing commutation failure forecast Control Algorithm, utilize the detection of inverter side direct current, ac bus zero sequence voltage component, abc-α β conversion and ac bus voltage effective value, establish the direct current prediction setting method that can be used for reducing Commutation Failure probability in 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 one side proposes suppresses the commutation failure PREDICTIVE CONTROL module of Commutation Failure supplementary perfect further to by means of only reduction trigger delay angle, increase angle of overlap; On the other hand, the basis of practicable commutation failure PREDICTIVE CONTROL module gives perfect while, point out that on commutation failure predictive control strategy, direct current controls this research direction further.

Accompanying drawing explanation

Fig. 1 is the inventive method flow chart;

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

Embodiment

Below in conjunction with the drawings and specific embodiments, illustrate the present invention further, these embodiments should be understood only be not used in for illustration of the present invention and limit the scope of the invention, after having read the present invention, the amendment of those skilled in the art to the various equivalent form of value of the present invention has all fallen within the application's claims limited range.

Be described in detail 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 solves the contradiction increasing angle of overlap and suppress commutation failure and systematic economy to run preferably, its basic thought is: when detecting that fault in ac transmission system may cause commutation failure, in inverter side trigger delay angle, deduct certain angle, realize triggering in advance.But known according to Related literature analysis, suppress Commutation Failure to have its inherent limitation by means of only reduction trigger delay angle, increase angle of overlap.According to the further analysis of commutation failure mechanism, the direct current PREDICTIVE CONTROL held water then can strengthen the control of control system to commutation process, to meet the necessary condition of inverter success commutation under 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 (symmetrical and asymmetric) of inverter side AC system, is detected with ac bus voltage zero sequence voltage with based on α bC-α β conversion respectively; And respectively compared with set point to determine whether to cause Commutation Failure, to start direct current PREDICTIVE CONTROL.The commutation failure PREDICTIVE CONTROL module direct current that the present invention relates to predicted value of adjusting gets following form:

I _{d_PREV}=2kI _{d_inv_2s}filter value-I _{d_inv}

In formula, I _{d_inv}for inverter 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}for the perunit value of inverter side AC system busbar voltage effective value; u _{aB_DIFF_MAXHOLD}for (the U that abc-α β converts _{α β _ 2s}filter value-U _{α β}) maximum 20ms retention value;

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

Fig. 2 is that the commutation failure direct current that the present invention relates to predicts 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 converts $u_{\mathrm{\α}}=(u_b-u_c)/\sqrt{3},u_{\mathrm{\β}}=$ $(2u_a-u_b-u_c)/3,$ 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 U respectively _{z_DIFF_MAXHOLD}and U _{aB_DIFF_MAXHOLD};

Z_DIFF_LEVEL and AB_DIFF_LEVEL is respectively in order to judge that AC system is asymmetric with in symmetric fault situation, and whether inverter commutation failure may occur, and judges that signal gives lasting 20ms.

Z_DIFF_GAIN and AB_DIFF_GAIN is U _{z_DIFF_MAXHOLD}with U _{aB_DIFF_MAXHOLD}non-zero weights, select corresponding component to export with the product of weights when module judges commutation failure may occur, otherwise output zero setting; Higher value is got in order to judge whether that needing to start direct current prediction setting value is controlled, and if so, then calculates commutation failure direct current prediction setting value I to the output of the two _{d_PREV}=2kI _{d_inv_2s}filter value-I _{d_inv}, otherwise I _{d_PREV}do not do commutation failure prediction to adjust, it is normal DC setting value I _{d_NOR}; I _{d_PREV}export direct current transportation pole key-course control system to, in order to suppress Commutation Failure.

Claims (1)

1. one kind is suppressed the direct current prediction setting method of commutation failure, be applied to Traditional DC transmission of electricity inverter side control system pole key-course, by detecting related electric amount, revise direct current setting value in this key-course when Commutation Failure may be there is, it 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}with α/β conversion difference Product-factor k _{aB_DIFF_LEVEL};

(2) inverter side direct current I is inputted _{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 commutation failure residual voltage V simultaneously _{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 the filtering that time constant filter is 2s, 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:

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

Wherein, u _α, u _βand U _{α β}for the correlative of Clarke conversion (α/β conversion), former three-phase voltage is simplified to two-phase, namely from three-phase A-B-C coordinate system transformation to two-phase alpha-beta coordinate system;

Zero-sequence component calculates:

U _Z＝|u _a+u _b+u _c|

(4) to U _{α β}carry out the filtering that time constant filter is 2s, 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 U respectively _{aB_DIFF_MAXHOLD}and U _{z_DIFF_MAXHOLD};

(5) U is judged _zwhether be more than or equal to V _{z_DIFF_LEVEL}, if so, calculate D _z=k _{z_DIFF_LEVEL}u _{z_DIFF_MAXHOLD}, otherwise D _z=0;

(6) judge whether be more than or equal to U _{aB_DIFF_LEVEL}, if so, 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}

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

(8) judge whether D is greater than zero, if so, then calculate direct current prediction setting value I during 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 DC setting value I _{d_NOR};

(9) I is exported _{d_PREV}.