CN105024393A - DC transmission system commutation area calculation method and commutation failure detection method - Google Patents

Abstract

The invention relates to a DC transmission system commutation area calculation method and a commutation failure detection method. The DC transmission system commutation area calculation method comprises the following steps: (1) time parameters uv, beta and Id in the case of system operation are detected; (2) upper and lower limits pi-beta and pi-gammamin of an integral interval within each period of AC line voltage are determined, wherein gammamin is the minimal extinction angle of an inverter (the intrinsic parameter of the system); (3) phase lock is carried out on uv and a waveform of the phase along with time changes is obtained; (4) according to the uv phase lock result and an inverter gating advance angle beta, an enabled pulse in the integral interval and an integral zeroing pulse beyond the integral interval are obtained; (5) according to the enabled pulse, the line voltage is sampled; and (6) the line voltage uv after sampling and the integral zeroing pulse are sent to an integrator at the same time, and the maximal commutation area as described in the description in each period is obtained. Through comparing the maximal commutation area obtained through calculation and the maximal commutation area needed by inverter, system dynamic features during the inverter commutation process can be reflected.

Description

A kind of DC transmission system commutation area computation method and commutation failure detection method

Technical field

The invention belongs to high-voltage dc transmission electrical domain, be specifically related to a kind of DC transmission system commutation area computation method and commutation failure detection method.

Background technology

Thyristor is as a kind of half control type power electronic device of technology maturation, and because it has large, the withstand voltage height of capacity, current most of HVDC (High Voltage Direct Current) transmission system is basic convertor unit with thyristor.Based in the HVDC (High Voltage Direct Current) transmission system of thyristor device, the commutation voltage that the commutation course of Inverter Station needs AC system to provide enough.Therefore, inverter for the fluctuation of AC system and fault very responsive, except overvoltage fall, except the factor such as AC fault can cause commutation failure, the alternating voltage waveform distortion that harmonic wave causes also causes commutation failure to occur.Therefore, commutation failure is a fault that cannot thoroughly eliminate for HVDC (High Voltage Direct Current) transmission system.

Because National energy distribution is unbalanced, economic developmental difference large, high voltage direct current transmission has very important meaning for the modernization construction of China.In recent years, had in China that many HVDC (High Voltage Direct Current) transmission line are grid-connected to put into operation, and along with the trend that economic development and energy resource structure make the transition, following DC power transmission line can be increasing.Therefore by there will be many DC power transmission line simultaneously drop point in the phenomenon in same area, form Multi-infeed HVDC transmission system in this region, this phenomenon at present in China south China, East China occurs.Different from single infeed HVDC Systems, when after a circuit generation commutation failure in Multi-infeed HVDC transmission system, except causing self drop point place power network fluctuation, also likely cause adjacent current conversion station generation commutation failure, thus serious threat is brought to the safety and stability of whole distract electric power system.Therefore, need carry out identification to commutation failure and precautionary measures are provided.

At present, in the identification of commutation failure, commutation area is adopted to be a kind of conventional method of discrimination as the criterion of commutation failure.There is no the maximum commutation area defining method that implementation is strong in prior art, the system dynamic characteristic of commutation process cannot be reflected.

Summary of the invention

The object of this invention is to provide a kind of DC transmission system commutation area computation method and commutation failure detection method, in order to solve the problem that cannot reflect the system dynamic characteristic of commutation process of the prior art.

For achieving the above object, the solution of the present invention comprises:

A kind of DC transmission system commutation area computation method, comprises the following steps:

(1) detection system real time execution parameter, i.e. inverter ac line voltage u _v, inverter gating advance angle β;

(2) integrating range bound [π-β, π-γ in ac line voltage each cycle is determined _min], wherein, γ _minfor inverter critical extinction angle (the intrinsic parameter of system);

(3) to the inverter ac line voltage u of actual measurement _vcarry out phase-locked, obtain the time dependent waveform of its phase place;

(4) according to ac line voltage u _vphase-locked Output rusults in conjunction with inverter gating advance angle β, the integrate-dump pulse outside the enabling pulse in formation product by stages and this integrating range;

(5) according to enabling pulse, line voltage is sampled;

(6) by the line voltage u after sampling _vbe sent to integrator with integrate-dump pulse simultaneously, obtain the maximum commutation area in each cycle $S_v={\∫}_{\mathrm{\π}-\mathrm{\β}}^{\mathrm{\π}-{\mathrm{\γ}}_{min}}{u}_v\left(\mathrm{\ω}t\right)d\mathrm{\ω}t.$

Described inverter side ac line voltage is real-time measured waveform in system cloud gray model.

A kind of DC transmission system commutation failure detection method, comprises the following steps:

(1) detection system real time execution parameter, i.e. inverter ac line voltage u _v, inverter gating advance angle β and direct current I _d;

(2) integrating range bound [π-β, π-γ in ac line voltage each cycle is determined _min], wherein, γ _minfor inverter critical extinction angle (the intrinsic parameter of system);

(3) to the inverter ac line voltage u of actual measurement _vcarry out phase-locked, obtain the time dependent waveform of its phase place;

(4) according to ac line voltage u _vphase-locked Output rusults in conjunction with inverter gating advance angle β, the integrate-dump pulse outside the enabling pulse in formation product by stages and this integrating range;

(5) according to enabling pulse, line voltage is sampled;

(6) by the line voltage u after sampling _vbe sent to integrator with integrate-dump pulse simultaneously, obtain the maximum commutation area in each cycle $S_v={\∫}_{\mathrm{\π}-\mathrm{\β}}^{\mathrm{\π}-{\mathrm{\γ}}_{min}}{u}_v\left(\mathrm{\ω}t\right)d\mathrm{\ω}t;$

(7) according to real-time parameter I _dcalculate the commutation area S that inverter needs, wherein, S=2L _r| I _d|, wherein, L _rfor commutation inductance (the intrinsic parameter of system);

(8) calculate the commutation area S of inverter needs according to real-time parameter and compare with the maximum commutation area Sv that AC system provides; As Sv>S, commutation process carries out smoothly; As Sv<S, inverter generation commutation failure.

Described inverter side ac line voltage is real-time measured waveform, S _vfor the maximum commutation area provided in each power frequency period of alternating voltage.

The commutation area that described inverter needs is: S=2L _r| I _d|, be the real-time commutation area needed in inverter commutation process.

The present invention, owing to taking above technical scheme, has the following advantages:

(1) adopt system cloud gray model real-time parameter, the transient response of commutation process can be reflected;

(2) with maximum commutation area for research object, computational process be simply easy to realize;

(3) result of calculation is the voltage time and area in each cycle, can locate the situation of each commutating period;

(4) situation of change of alternating voltage can be real-time monitored, can fast reaction be made to AC fault;

(5) contrast of result of calculation and inverter commutation area, can intuitively as commutation failure generation criterion.

Accompanying drawing explanation

Fig. 1 is the graph of a relation of HVDC (High Voltage Direct Current) transmission system inverter commutation process neutral voltage;

Fig. 2 is the flow chart of DC transmission system commutation failure detection method embodiment of the present invention;

Fig. 3 is ac line voltage phase-locked loop Output rusults figure;

Fig. 4 is ac line voltage integrating range enabling pulse and quenching pulse schematic diagram;

Fig. 5 inverter side ac line voltage sampled result schematic diagram;

The alternating voltage time and area schematic diagram that Fig. 6 integrator exports;

The commutation area schematic diagram of Fig. 7 HVDC (High Voltage Direct Current) transmission system alternating voltage time and area and needs.

Embodiment

First the process of the invention is analyzed.

Based on the HVDC (High Voltage Direct Current) transmission system of thyristor converter device, in the commutation course of Inverter Station, need the commutation voltage that AC provides enough.When alternating voltage causes wave distortion due to factors such as harmonic waves, commutation process also possibly cannot carry out smoothly.Therefore, in actual motion, the principal element that commutation failure occurs is fault in ac transmission system.

The commutation process of inverter with exchange the relation of side line voltage as shown in Figure 1.In commutation process, the converting commutating current on brachium pontis and the relation exchanged between side line voltage as follows:

$u_v\left(t\right)=L_r\frac{{\mathrm{di}}_3}{dt}-L_r\frac{{\mathrm{di}}_1}{dt}---\left(1\right)$

i ₃+i ₁＝I _d(2)

Wherein, u _vfor exchanging side line voltage, i ₁and i ₃be respectively the electric current on brachium pontis 1 and brachium pontis 3, I _dfor direct current, L _rfor commutation inductance value, it is the intrinsic parameter of system.

In commutation process, if rectification side adopts is Given current controller, or think that the smoothing reactor of direct current system is very large, so can think I _dfor steady state value or change very little.In commutation process inverter ac side there is following relation in voltage:

$u_v\left(t\right)=2L_r\frac{{\mathrm{di}}_3}{dt}---\left(3\right)$

As shown in Figure 1, in commutation process, at t ₁in the moment, the electric current on brachium pontis 3 is zero; At t ₂in the moment, the electric current on brachium pontis 3 is direct current I _d.Time [t is carried out to above formula both sides simultaneously ₁, t ₂] upper integral:

${\&Integral;}_{t_1}^{t_2}{u}_v\left(t\right)dt=2L_r{\&Integral;}_{t_1}^{t_2}\frac{{\mathrm{di}}_3}{dt}dt=2L_r{I}_d---\left(4\right)$

In above formula, levoform is alternating voltage integral result on a timeline, regards the area that voltage waveform and time shaft surround as.

Therefore, in commutation process, the commutation area that inverter needs is as follows:

S＝2L _r|I _d| (5)

As can be seen from formula (4), the commutation area of system each time required by commutation process is relevant with current current value, and alternating voltage time and area is then all relevant to alternating voltage waveform, inverter gating advance angle, commutation overlap angle.

Therefore, in commutation process, the maximum commutation area that AC system can provide is as follows:

$S_v={\&Integral;}_{\mathrm{\&pi;}-\mathrm{\&beta;}}^{\mathrm{\&pi;}-{\mathrm{\&gamma;}}_{min}}{u}_v\left(\mathrm{\&omega;}t\right)d\mathrm{\&omega;}t---\left(6\right)$

Wherein, S _vfor the maximum commutation area that ac line voltage provides, β is inverter gating advance angle, and γ min is the critical extinction angle of inversion oneself requirement, u _vfor inverter ac line voltage.

In above formula, only has u _vbeing variable with β, is the real-time parameter of system cloud gray model.Therefore S _vsolution procedure in simple, the correctness of result of calculation can be ensured simultaneously.

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

DC transmission system commutation area computation method embodiment

DC transmission system commutation area computation method of the present invention comprises the following steps:

(1) detection system real time execution parameter, i.e. inverter ac line voltage u _v, inverter gating advance angle β.

Set up the simulation analysis model of HVDC (High Voltage Direct Current) transmission system, and obtain the relevant parameter in system operation by this system model measurement.

(2) integrating range bound [π-β, π-γ in ac line voltage each cycle is determined _min], wherein, γ _minfor inverter critical extinction angle (the intrinsic parameter of system).

(3) to the inverter ac line voltage u of actual measurement _vcarry out phase-locked, obtain the time dependent waveform of its phase place;

As described in Figure 3, u is obtained from systematic survey system _vreal-time waveform, and by Waveform Input in phase-locked loop, obtain the output sawtooth waveforms of phase place, by the PGC demodulation of line voltage.Sawtooth and line voltage waveform correspondence, the periodic waveform of change between spending from 0 to 360.

(4) according to ac line voltage u _vphase-locked Output rusults in conjunction with inverter gating advance angle β, the integrate-dump pulse outside the enabling pulse in formation product by stages and this integrating range.

As shown in Figure 4, according to integrating range and phase output sawtooth waveforms, in pulse generator, produce one-period pulse, each cycle π of the corresponding each line voltage of rising edge of a pulse-β phase Angle Position, the corresponding π-γ of trailing edge _minphase Angle Position, becomes enabling pulse.

Maximum commutation area should be the calculated value in each cycle, therefore quenching pulse is needed to ensure integral result, line voltage-phase sawtooth waveforms is input in pulse generator, generates the cycle burst pulse that a rising edge is line voltage each cycle π angle position, become quenching pulse.

(5) according to enabling pulse, line voltage is sampled.

As shown in Figure 5, enabling pulse and voltage waveform are input in multiplier, enabling pulse amplitude is " 1 " simultaneously, ac line voltage u in multiplier Output rusults _vdiscrete.The u that Output rusults is formed _v1the each cycle inherence of line voltage [π-β, π-γ _min] between the sampled result of waveform.

(6) by the line voltage u after sampling _vbe sent to integrator with integrate-dump pulse simultaneously, obtain the maximum commutation area S in each cycle _v.

By discrete line voltage u _v1be input in integrator with quenching pulse, through integral element, the result of output is u _vat [π-β, π-γ within each cycle _min] between integrated value.In each cycle, from π-β phase angle, integrated value increases, gradually to π-γ _minafter no longer increase, and then obtain formula (6): described in AC system each cycle maximum commutation area value S that can provide _v.Again through the effect of π position quenching pulse, ensure the maximum commutation area S that in each cycle, AC system provides _vcorrectness.

Commutation failure detection method embodiment:

As shown in Figure 2, DC transmission system commutation failure detection method of the present invention comprises the following steps:

(1) detection system real time execution parameter, i.e. inverter ac line voltage u _v, inverter gating advance angle β and direct current I _d.

Set up the simulation analysis model of HVDC (High Voltage Direct Current) transmission system, and obtain the relevant parameter in system operation by this system model measurement.

(2) integrating range bound [π-β, π-γ in ac line voltage each cycle is determined _min], wherein, γ _minfor inverter critical extinction angle (the intrinsic parameter of system).

(3) to the inverter ac line voltage u of actual measurement _vcarry out phase-locked, obtain the time dependent waveform of its phase place;

As described in Figure 3, u is obtained from systematic survey system _vreal-time waveform, and by Waveform Input in phase-locked loop, obtain the output sawtooth waveforms of phase place, by the PGC demodulation of line voltage.Sawtooth and line voltage waveform correspondence, the periodic waveform of change between spending from 0 to 360.

(4) enabling pulse and integrate-dump pulse is generated

According to ac line voltage u _vphase-locked Output rusults in conjunction with inverter gating advance angle β, the integrate-dump pulse outside the enabling pulse in formation product by stages and this integrating range.

As shown in Figure 4, according to integrating range and phase output sawtooth waveforms, in pulse generator, produce one-period pulse, each cycle π of the corresponding each line voltage of rising edge of a pulse-β phase Angle Position, the corresponding π-γ of trailing edge _minphase Angle Position, becomes enabling pulse.

Maximum commutation area should be the calculated value in each cycle, therefore quenching pulse is needed to ensure integral result, line voltage-phase sawtooth waveforms is input in pulse generator, generates the cycle burst pulse that a rising edge is line voltage each cycle π angle position, become quenching pulse.

(5) according to enabling pulse, line voltage is sampled.

As shown in Figure 5, enabling pulse and voltage waveform are input in multiplier, enabling pulse amplitude is " 1 " simultaneously, ac line voltage u in multiplier Output rusults _vdiscrete.The u that Output rusults is formed _v1the each cycle inherence of line voltage [π-β, π-γ _min] between the sampled result of portion waveshape.

(6) by the line voltage u after sampling _vbe sent to integrator with integrate-dump pulse simultaneously, obtain the maximum commutation area S in each cycle _v.

As described in Figure 6, by discrete line voltage u _v1be input in integrator with quenching pulse, through integral element, the result of output is u _vat [π-β, π-γ within each cycle _min] between integrated value.In each cycle, from π-β phase angle, integrated value increases, gradually to π-γ _minafter no longer increase, and then obtain formula (6): described in AC system each cycle maximum commutation area value S that can provide _v.Again through the effect of π position quenching pulse, ensure the maximum commutation area S that in each cycle, AC system provides _vcorrectness.

(7) according to real-time parameter I _dcalculate the commutation area S that inverter needs, wherein, S=2L _r| I _d|, wherein, L _rfor commutation inductance (the intrinsic parameter of system).

(8) the commutation area S that inverter needs is calculated and the maximum commutation area S provided with AC system according to real-time parameter _vcompare.

As shown in Figure 7, by the result S of integrator output _vthe commutation area S needed with inverter compares output, just can as the Real-Time Monitoring result of commutation failure.

In normal operation, the maximum commutation area S that AC system provides _v>S; Work as S _vduring <S, at [π-β, π-γ _min] interior commutation process cannot complete smoothly, the increase of commutation time finally causes γ to be less than γ _min, inverter generation commutation failure.

Therefore, when AC generation voltage fluctuation and harmonic wave jitterbug, S _vcan reflect in real time, according to S _vwith S variation relation between the two, send early warning information for precautionary measures in commutation failure generation forward direction control system and reference is provided.

Claims (3)

1. a DC transmission system commutation area computation method, is characterized in that: comprise the following steps:

(1) detection system real time execution parameter, i.e. inverter ac line voltage u _v, inverter gating advance angle β;

(2) integrating range bound [π-β, π-γ in ac line voltage each cycle is determined _min], wherein, γ _minfor inverter critical extinction angle;

(3) to the inverter ac line voltage u of actual measurement _vcarry out phase-locked, obtain the time dependent waveform of its phase place;

(4) according to ac line voltage u _vphase-locked Output rusults in conjunction with inverter gating advance angle β, the integrate-dump pulse outside the enabling pulse in formation product by stages and this integrating range;

(5) according to enabling pulse, line voltage is sampled;

(6) by the line voltage u after sampling _vbe sent to integrator with integrate-dump pulse simultaneously, obtain the maximum commutation area in each cycle

2. DC transmission system commutation area computation method according to claim 1, is characterized in that: described inverter side ac line voltage is for measuring the waveform obtained in real time, S _vfor the maximum commutation area provided in real time in each power frequency period of alternating voltage.

3. a DC transmission system commutation failure detection method, is characterized in that: comprise the following steps:

(1) detection system real time execution parameter, i.e. inverter ac line voltage u _v, inverter gating advance angle β and direct current I _d;

(2) integrating range bound [π-β, π-γ in ac line voltage each cycle is determined _min], wherein, γ _minfor inverter critical extinction angle;

(3) to the inverter ac line voltage u of actual measurement _vcarry out phase-locked, obtain the time dependent waveform of its phase place;

(4) according to inversion test cross line voltage u _vphase-locked Output rusults in conjunction with inverter gating advance angle β, the integrate-dump pulse outside the enabling pulse in formation product by stages and this integrating range;

(5) according to enabling pulse, line voltage is sampled;

(6) by the line voltage u after sampling _vbe sent to integrator with integrate-dump pulse simultaneously, obtain the maximum commutation area in each cycle

(7) according to real-time parameter I _dcalculate the commutation area S that inverter needs, wherein, S=2L _r| I _d|, L _rfor commutation inductance;

(8) the commutation area S needed by inverter also compares with the maximum commutation area Sv that AC system provides; As Sv>S, commutation process carries out smoothly; As Sv<S, inverter generation commutation failure.