CN103500261B - Method for fault simulation of direct - Google Patents

Abstract

A kind of method for fault simulation of direct, step is as follows: 1: according to short trouble scene, has judged whether that straight-flow system is positioned at same electrical island with it, and if not, then straight-flow system does not take any operation; 2: if having straight-flow system and the position of fault to be positioned at same electrical island, then whether the failure judgement duration is less than the actuation time of straight-flow system 100Hz harmonic wave, zero-sequence current and commutation failure protection, if so, enters step 5, otherwise enters step 3; 3: in this island, carry out the calculating of ac bus short-circuit voltage; 4: judge whether protection starts according to short trouble type; 5: according to failure message, judge whether that the stable control strategy of DC line needs to start.If so, the operation of power setting adjustment is then performed according to Policy Table.Otherwise exit; The present invention can avoid and utilizes simulation software to carry out modeling and transient emulation to straight-flow system, and guarantees that the response of DC transmission system has enough precision when simulating ac and dc systems fault.

Description

Method for fault simulation of direct

Technical field

The present invention relates to electric power system fault sunykatuib analysis technical field, be specifically related to a kind of method for fault simulation of direct.

Background technology

Along with the development of power industry, nowadays the form of extensive interconnected network is formed gradually.As one of the most complicated industrial system that the mankind set up, bulk power grid is while generation economies of scale, lifting operational management efficiency, too increase the complicacy of self, make fluctuation, accident easily brings wide influence and more serious consequence more.Therefore, in order to the loss taken precautions against and reduction accident causes, the failure response simulation of electrical network has great importance.

Compare ac transmission, direct current transportation has as transmitted power size and direction can quick adjustment controls, performance driving economy is good and can the unique advantage such as built by separate periods, can realize high voltage, long apart from, Large Copacity power transmission and asynchronous networking.In recent years, the DC power transmission line quantity that puts into operation increases gradually, and nowadays, Ac/dc Power Systems is of common occurrence.As China, except North China, Central China Power Grid, other regional power grids have realized interconnected all by direct current.And there is the area of large-scale blackout, be also no lack of the electrical network comprising interchange, direct current two parts.

Because ac and dc systems contact is tight, in commingled system, when an error occurs, influencing each other therebetween can not be ignored.The Simulation and analysis of change to failure response of electrical network proposes new requirement, must think better of the factor of wherein direct current.

Because the control section of straight-flow system is comparatively complicated, the scholar of the relevant problem of great majority, when carrying out fault simulation and analyzing, selects to adopt the straight-flow system model in simulation software or to go forward side by side Mobile state simulation calculation to straight-flow system again modeling.JingzheTu; DeqiangGan; HuanhaiXin; When ZhenWang simulates the fault of ac and dc systems in " CascadingFailureandBlackoutRiskAnalysisofAC/DCPowerSyste m-TheImpactofAC/DCInterconnectionModeandCapacityDistribu tion ", be and utilize the straight-flow system quasi steady state model in PSS/E to carry out transient emulation.But in this model, the criterion of DC system locking is single, and implication is failed to understand.For the straight-flow system of reality, there is many factors that can cause locking, such as commutation line voltage zero-cross point offsets, zero-sequence current is excessive, 100Hz harmonic amplitude is excessively high, therefore requires more criterion.In addition, the effect of the stability control equipment installed in actual DC system do not considered by model.Meanwhile, carry out calculated amount in simulation process being caused large compared with Accurate Model to straight-flow system, make simulation time longer.Therefore a kind of failure simulation method of DC transmission system is needed, this method considers the multiple situation that may cause DC system locking, and in the process of analog DC transmission system failure response, do not adopt transient emulation, to reduce calculated amount and to shorten the time emulated.

Summary of the invention

In order to solve above-mentioned prior art Problems existing, the object of the present invention is to provide a kind of method for fault simulation of direct, can avoid and utilize simulation software to carry out modeling and transient emulation to straight-flow system, and guarantee that the response of DC transmission system has enough precision when simulating ac and dc systems fault.

For reaching above object, the present invention adopts following technical scheme:

A kind of method for fault simulation of direct, comprises the steps:

Step 1: according to short trouble scene, has judged whether that straight-flow system is positioned at same electrical island with it, and if not, then straight-flow system does not take any operation;

Step 2: if having straight-flow system and the position of fault to be positioned at same electrical island, then whether the failure judgement duration is less than the actuation time of straight-flow system 100Hz harmonic wave, zero-sequence current and commutation failure protection, if so, enters step 5, otherwise enters step 3;

Step 3: carry out the calculating of ac bus short-circuit voltage in this island, obtains the ac bus short-circuit voltage of straight-flow system rectification side and inverter side;

Step 4: judge whether protection starts according to short trouble type;

1) when there is single-phase or line to line fault earth fault, if straight-flow system either side ac bus voltage lower than the 100Hz overcurrent protection voltage starting value under this kind of fault and trouble duration be longer than protection start-up time, then locking straight-flow system; If straight-flow system is non-latching, then judge that the now change of current becomes the protection of neutral point zero sequence excess current and whether starts, start then locking straight-flow system;

2) when there is three-phase shortcircuit earth fault, if straight-flow system inverter side ac bus voltage is lower than the voltage starting value of this protection and trouble duration is longer than protection start-up time, then locking straight-flow system.

Step 5: for the straight-flow system of not yet locking, according to failure message, judges whether that the stable control strategy of DC line needs to start, if so, then performs the operation of power setting adjustment according to Policy Table, otherwise exit.

Calculating ac bus short-circuit voltage described in step 2, calculating be each busbar voltage in three-phase shortcircuit situation, concrete grammar is as follows:

Step 1: ignore DC line in straight-flow system, AC portion circuit is formed admittance battle array, and master section is with next transient state reactance grounded;

Step 2: DC line is equivalent to alternating current circuit parameter, add admittance battle array, method is as follows:

If the rectification side of DC line is i side, inverter side is j side, at known DC line two side bus alternating voltage U _i, U _j, and both sides current conversion station absorbed power P _i, P _j, Q _i, Q _jwhen, utilize following formula (1), formula (2), formula (3) and formula (4) to carry out equivalence to DC line:

In formula: g is equivalent AC wired in series conductance, b is equivalent AC wired in series susceptance, b _i0for equivalent AC wire rectification side shunt susceptance, b _j0for equivalent AC wire inverter side shunt susceptance;

Concrete steps are:

1) utilize simulation software, three phase short circuit fault is set at DC line i side bus, carry out simulation calculation, obtain the alternating voltage U of DC line two side bus of moment after short circuit _i, U _j, and both sides current conversion station absorbed power P _i, P _j, Q _i, Q _j, calculate g, b, b by formula (1), formula (2), formula (3) _i0, and press y _ij=g+bi asks for y _ij, wherein, y _ijfor equivalent AC circuit is by the series admittance of rectification side i to inverter side j;

2) utilize simulation software, three phase short circuit fault is set at DC line j side bus, carry out simulation calculation, obtain the alternating voltage U of DC line two side bus of moment after short circuit _i, U _j, and both sides current conversion station absorbed power P _i, P _j, Q _i, Q _j, calculate g, b, b by formula (1), formula (2), formula (4) _j0, and press y _ji=g+bi asks for y _ji, wherein, y _jifor equivalent AC circuit is by the series admittance of inverter side j to rectification side i;

3) y will obtained _ij, y _ji, b _i0, b _j0add admittance battle array;

Step 3: admittance battle array is converted into Impedance Matrix;

Step 4: set the ac bus of the fault that is short-circuited as f, during normal operation, its voltage phasor is short circuit grounding impedance is Z _f, then by the short-circuit current on ac bus f flow direction ground be:

${\stackrel{\·}{I}}_f=\frac{{\stackrel{\·}{U}}_{f0}}{Z_{\mathrm{ff}}+Z_f}$

Wherein: Z _ffrepresent the self-impedance at node f place, the element that namely in Impedance Matrix, the capable f of f arranges;

Step 5: set and require that the bus of power taking pressure is as m, can calculate wherein, represent false voltage component, Z _mfrepresent the transimpedance between node m and node f, the element that namely in Impedance Matrix, the capable f of m arranges;

Step 6: establish when normally running, bus m voltage is then its short-circuit voltage for:

${\stackrel{\·}{U}}_m={\stackrel{\·}{U}}_{m0}+\mathrm{\Δ}{\stackrel{\·}{U}}_m$

Wherein: represent false voltage component.

The concrete grammar carrying out power adjustment according to steady control strategy described in step 4 is: judge whether stability control equipment has corresponding power control strategy; If have, then run according to tactful Variable power, if not, then judge whether rectification busbar voltage drops to ultimate value; If so, then current setting is reduced to 90% or change straight-flow system operate power according to busbar voltage, limit Trigger Angle, current setting result of calculation, if not, then straight-flow system operate power is constant.

Described steady control strategy comprises as follows:

1) when DC line generation locking, the load in excision inverter side AC network;

2) when the alternating current circuit in parallel with DC line break down cause transmission to stop time, start the power ascension function of straight-flow system;

3) when converting plant exchanges inlet wire fault or inverter side outlet fault, straight-flow system transmission power is reduced.

Compared to the prior art, tool has the following advantages in the present invention:

By adopting the failure simulation method of DC transmission system of the present invention, can avoid and utilize simulation software to carry out modeling and transient emulation to straight-flow system, and guarantee when simulating ac and dc systems fault, the response of DC transmission system has enough precision, the object of reach and promote computing velocity, saving simulation time.Specifically, tool has the following advantages:

1) consider 100Hz excess current, change of current change neutral point zero sequence excess current and commutation failure to the impact of straight-flow system, the precision simulated is improved.

2) simulate the steady control strategy of stability control equipment, the failure response of straight-flow system is controlled, reality of more fitting.

3) in the present invention, only need to carry out a transient emulation when obtaining DC line equivalent AC parameter, compare and utilize transient emulation to calculate short-circuit voltage, utilize the transient emulation analog DC system failure to respond, effectively improve computing velocity, save computing time.

Accompanying drawing explanation

Accompanying drawing is the inventive method process flow diagram.

Embodiment

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

Step 1: according to short trouble scene, has judged whether that straight-flow system is positioned at same electrical island with it, and if not, then straight-flow system does not take any operation;

Step 2: if having straight-flow system and the position of fault to be positioned at same electrical island, then whether the failure judgement duration is less than the actuation time of straight-flow system 100Hz harmonic wave, zero-sequence current and commutation failure protection, if so, enters step 5, otherwise enters step 3;

Step 3: carry out the calculating of ac bus short-circuit voltage in this island, obtains the ac bus short-circuit voltage of straight-flow system rectification side and inverter side;

Calculating ac bus short-circuit voltage described above, calculating be each busbar voltage in three-phase shortcircuit situation, concrete grammar is as follows:

One: ignore DC line in straight-flow system, AC portion circuit is formed admittance battle array, and master section is with next transient state reactance grounded;

Two: DC line is equivalent to alternating current circuit parameter, add admittance battle array, method is as follows:

If the rectification side of DC line is i side, inverter side is j side, at known DC line two side bus alternating voltage U _i, U _j, and both sides current conversion station absorbed power P _i, P _j, Q _i, Q _jwhen, utilize following formula (1), formula (2), formula (3) and formula (4) to carry out equivalence to DC line:

In formula: g is equivalent AC wired in series conductance, b is equivalent AC wired in series susceptance, b _i0for equivalent AC wire rectification side shunt susceptance, b _j0for equivalent AC wire inverter side shunt susceptance;

Concrete steps are:

1) utilize simulation software, three phase short circuit fault is set at DC line i side bus, carry out simulation calculation, obtain the alternating voltage U of DC line two side bus of moment after short circuit _i, U _j, and both sides current conversion station absorbed power P _i, P _j, Q _i, Q _j, calculate g, b, b by formula (1), formula (2), formula (3) _i0, and press y _ij=g+bi asks for y _ijy _ij, wherein, y _ijfor equivalent AC circuit is by the series admittance of rectification side i to inverter side j;

2) utilize simulation software, three phase short circuit fault is set at DC line j side bus, carry out simulation calculation, obtain the alternating voltage U of DC line two side bus of moment after short circuit _i, U _j, and both sides current conversion station absorbed power P _i, P _j, Q _i, Q _j, calculate g, b, b by formula (1), formula (2), formula (4) _j0, and press y _ji=g+bi asks for y _ji, wherein, y _jifor equivalent AC circuit is by the series admittance of inverter side j to rectification side i;

3) y will obtained _ij, y _ji, b _i0, b _j0add admittance battle array;

Three: admittance battle array is converted into Impedance Matrix;

Four: set the ac bus of the fault that is short-circuited as f, during normal operation, its voltage phasor is short circuit grounding impedance is Z _f, then by the short-circuit current on ac bus f flow direction ground be:

${\stackrel{\·}{I}}_f=\frac{{\stackrel{\·}{U}}_{f0}}{Z_{\mathrm{ff}}+Z_f}$

In formula: Z _ffrepresent the self-impedance at node f place, the element that namely in Impedance Matrix, the capable f of f arranges;

Five: set and require that the bus of power taking pressure is as m, can calculate wherein, represent false voltage component, Z _mfrepresent the transimpedance between node m and node f, the element that namely in Impedance Matrix, the capable f of m arranges;

Six: establish when normally running, bus m voltage is then its short-circuit voltage for:

${\stackrel{\·}{U}}_m={\stackrel{\·}{U}}_{m0}+\mathrm{\Δ}{\stackrel{\·}{U}}_m$

Wherein: represent false voltage component.

Step 4: judge whether protection starts according to short trouble type;

1) when there is single-phase or line to line fault earth fault, if straight-flow system either side ac bus voltage lower than the 100Hz overcurrent protection voltage starting value under this kind of fault and trouble duration be longer than protection start-up time, then locking straight-flow system; If straight-flow system is non-latching, then judge that the now change of current becomes the protection of neutral point zero sequence excess current and whether starts, start then locking straight-flow system;

2) when there is three-phase shortcircuit earth fault, if straight-flow system inverter side ac bus voltage is lower than the voltage starting value of this protection and trouble duration is longer than protection start-up time, then locking straight-flow system.

Trouble duration: using the moment of harmonics excision fault as the end time of fault in the present invention.Consider malfunction and the tripping of protection, its actuation time is a stochastic variable.According to the actual count data of harmonics actuation time, can by its probability density function of Weibull distribution matching.During fault simulation, generate a random number, as the duration of this fault by this probability density function.

When AC system breaks down, in straight-flow system, the protection of the easiest action has 100Hz overcurrent protection, the zero sequence excess current protection of change of current change neutral point and commutation failure protection.Namely the present invention simulates these three kinds protections.Below these three kinds of protections are described in detail.

1) 100Hz overcurrent protection

After asymmetric earth fault occurs AC system, 100Hz excess current can be produced.When protecting the 100Hz electric current detected in DC line to reach setting value and after certain time, the startup of 100Hz overcurrent protection, locking straight-flow system.

Adopt the voltage swing of straight-flow system ac bus when fault to estimate the size of 100Hz electric current in the present invention.

Adopting simulation software to emulate there is all kinds of asymmetry short circuit fault in system everywhere, obtaining the magnitude of voltage of straight-flow system ac bus when straight-flow system 100Hz electric current under dissimilar short trouble reaches protection initiation value.When straight-flow system ac bus Voltage Drop is to this value, then think that 100Hz electric current has reached protection initiation value.

Owing to only carrying out the calculating of three-phase shortcircuit voltage in the present invention, therefore need carry out three phase short circuit fault experiment in same place, the magnitude of voltage of straight-flow system ac bus when there is three phase short circuit fault under obtaining the same terms, as the voltage criterion that protection starts.

In fault simulation process, when straight-flow system ac bus voltage lower than protection start voltage criterion, and trouble duration be longer than protection start-up time time, starting protection, locking straight-flow system.

2) change of current becomes the protection of neutral point zero sequence excess current

During AC system generation unbalanced fault, zero-sequence current can be produced.When protection detects that the zero-sequence current amplitude of change of current change neutral point is too high, the change of current becomes the protection of neutral point zero sequence excess current and starts, locking straight-flow system.

The analogy method of this protection is substantially identical with the analogy method of 100Hz overcurrent protection; emulation is just needed to obtain under various unbalanced short circuit fault occurs system; straight-flow system change of current change neutral point zero sequence excess current reaches ac bus Voltage Drop during initiation value; test again, using the corresponding ac bus voltage in three-phase shortcircuit situation as protection voltage starting value.

3) commutation failure protection

When continuous commutation failure occurs straight-flow system, protection starts, and carries out locking.

The minimum bus voltage that can obtain AC system generation three phase short circuit fault straight-flow system generation in season commutation failure is:

$E_{\min }=\frac{\sqrt{2}{X}_r{I}_d}{\cos {\mathrm{\γ}}_{\min }-\cos \mathrm{\β}}$

Because commutation failure generally occurs in straight-flow system inverter side, in the present invention, when straight-flow system inverter side ac bus voltage is lower than this value and certain time, think that continuous commutation failure occurs system, starting protection.

Due to unsymmetrical short-circuit earth fault occur time, the Voltage Drop of ac bus is mostly unlikely causes continuous commutation failure, and completely likely occurs breaking down in some place, and straight-flow system commutation failure does not occur, and but causes the situation of 100Hz protection act.Therefore, when non-three-phase ground fault occurs, the startup of commutation failure protection can be included in the situation of 100Hz overcurrent protection startup.

Step 5: for the straight-flow system of not yet locking, according to failure message, judges whether that the stable control strategy of DC line needs to start, if so, then performs the operation of power setting adjustment according to Policy Table, otherwise exit.Power setting adjustment concrete grammar is: judge whether stability control equipment has corresponding power control strategy; If have, then a tactful Variable power runs, and if not, then judges whether rectification busbar voltage drops to ultimate value; If so, then current setting is reduced to 90% or change straight-flow system operate power according to busbar voltage, limit Trigger Angle, current setting result of calculation, if not, then straight-flow system operate power is constant.

Several conventional strategy of stability control equipment is simulated in the present invention, specific as follows:

1) when DC line generation locking, the load in excision inverter side AC network;

2) when the alternating current circuit in parallel with DC line break down cause transmission to stop time, start the power ascension function of straight-flow system;

3) when converting plant exchanges inlet wire fault or inverter side outlet fault, straight-flow system transmission power is reduced.

The above is only the preferred embodiment of the present invention; it should be pointed out that for those skilled in the art, under the prerequisite not departing from the technology of the present invention principle; can also make some improvement and distortion, these improve and distortion also should be considered as protection scope of the present invention.

Claims (4)

1. a method for fault simulation of direct, is characterized in that: comprise the steps:

Step 1: according to short trouble scene, has judged whether that straight-flow system is positioned at same electrical island with it, and if not, then straight-flow system does not take any operation;

Step 2: if having straight-flow system and the position of fault to be positioned at same electrical island, then whether the failure judgement duration is less than the actuation time of straight-flow system 100Hz harmonic wave, zero-sequence current and commutation failure protection, if so, enters step 5, otherwise enters step 3;

Step 3: carry out the calculating of ac bus short-circuit voltage in this island, obtains the ac bus short-circuit voltage of straight-flow system rectification side and inverter side;

Step 4: judge whether protection starts according to short trouble type;

1) when there is single-phase or line to line fault earth fault, if straight-flow system either side ac bus voltage lower than the 100Hz overcurrent protection voltage starting value under this kind of fault and trouble duration be longer than protection start-up time, then locking straight-flow system; If straight-flow system is non-latching, then judge that the now change of current becomes the protection of neutral point zero sequence excess current and whether starts, start then locking straight-flow system;

2) when there is three-phase shortcircuit earth fault, if straight-flow system inverter side ac bus voltage is lower than the voltage starting value of this protection and trouble duration is longer than protection start-up time, then locking straight-flow system;

Step 5: for the straight-flow system of not yet locking, according to failure message, judges whether that the stable control strategy of DC line needs to start, and if so, then carries out power adjustment according to steady control strategy, otherwise exits.

2. method for fault simulation of direct according to claim 1, is characterized in that: the calculating ac bus short-circuit voltage described in step 3, calculating be each busbar voltage in three-phase shortcircuit situation, concrete grammar is as follows:

Step 1: ignore DC line in straight-flow system, AC portion circuit is formed admittance battle array, and master section is with next transient state reactance grounded;

Step 2: DC line is equivalent to alternating current circuit parameter, add admittance battle array, method is as follows:

If the rectification side of DC line is i side, inverter side is j side, at known DC line two side bus alternating voltage U _i, U _j, and both sides current conversion station absorbed power P _i, P _j, Q _i, Q _jwhen, utilize following formula (1), formula (2), formula (3) and formula (4) to carry out equivalence to DC line:

In formula: g is equivalent AC wired in series conductance, b is equivalent AC wired in series susceptance, b _i0for equivalent AC wire rectification side shunt susceptance, b _j0for equivalent AC wire inverter side shunt susceptance;

Concrete steps are:

1) utilize simulation software, three phase short circuit fault is set at DC line i side bus, carry out simulation calculation, obtain the alternating voltage U of DC line two side bus of moment after short circuit _i, U _j, and both sides current conversion station absorbed power P _i, P _j, Q _i, Q _j, calculate g, b, b by formula (1), formula (2), formula (3) _i0, and press y _ij=g+bi asks for y _ij, wherein, y _ijfor equivalent AC circuit is by the series admittance of rectification side i to inverter side j;

2) utilize simulation software, three phase short circuit fault is set at DC line j side bus, carry out simulation calculation, obtain the alternating voltage U of DC line two side bus of moment after short circuit _i, U _j, and both sides current conversion station absorbed power P _i, P _j, Q _i, Q _j, calculate g, b, b by formula (1), formula (2), formula (4) _j0, and press y _ji=g+bi asks for y _ji, wherein, y _jifor equivalent AC circuit is by the series admittance of inverter side j to rectification side i;

3) y will obtained _ij, y _ji, b _i0, b _j0add admittance battle array;

Step 3: admittance battle array is converted into Impedance Matrix;

Step 4: set the ac bus of the fault that is short-circuited as f, during normal operation, its voltage phasor is short circuit grounding impedance is Z _f, then by the short-circuit current on ac bus f flow direction ground be:

${\stackrel{\·}{I}}_f=\frac{{\stackrel{\·}{U}}_{f0}}{Z_{ff}+Z_f}$

Wherein: Z _ffrepresent the self-impedance at node f place, the element that namely in Impedance Matrix, the capable f of f arranges;

Step 5: set and require that the bus of power taking pressure is as m, can calculate wherein, represent false voltage component, Z _mfrepresent the transimpedance between node m and node f, the element that namely in Impedance Matrix, the capable f of m arranges;

Step 6: establish when normally running, bus m voltage is then its short-circuit voltage for:

${\stackrel{\·}{U}}_m={\stackrel{\·}{U}}_{m0}+\mathrm{\Δ}{\stackrel{\·}{U}}_m$

Wherein: represent false voltage component.

3. method for fault simulation of direct according to claim 1, is characterized in that: the concrete grammar carrying out power adjustment according to steady control strategy described in step 5 is: judge whether stability control equipment has corresponding power control strategy; If have, then run according to tactful Variable power, if not, then judge whether rectification busbar voltage drops to ultimate value; If so, then current setting is reduced to 90% or change straight-flow system operate power according to busbar voltage, limit Trigger Angle, current setting result of calculation, if not, then straight-flow system operate power is constant.

4. method for fault simulation of direct according to claim 3, is characterized in that: described steady control strategy comprises as follows:

1) when DC line generation locking, the load in excision inverter side AC network;

2) when the alternating current circuit in parallel with DC line break down cause transmission to stop time, start the power ascension function of straight-flow system;

3) when converting plant exchanges inlet wire fault or inverter side outlet fault, straight-flow system transmission power is reduced.