CN107064714A - MMC HVDC transmission line fault detection methods based on unilateral transient current - Google Patents
MMC HVDC transmission line fault detection methods based on unilateral transient current Download PDFInfo
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Abstract
A kind of MMC HVDC transmission line fault detection methods based on unilateral transient current, by being sampled to electric current in DC line, when meeting DC line electric current update condition, update DC line current value Idc；Then carry out failure and there is judgement, work as Iop>IsetIWhen system there is failure and calculate DC line electric current natural mode of vibration Energy-Entropy H, when meeting when DC side failure criterion, i.e. DC side have failure structure Fault Identification criterion, according to Fault Identification criterion failure judgement type.The present invention can be quickly detected DC side failure；By moving average filter extraction curent change trend, fast response time, fault type recognition is accurately and reliably.
Description
Technical field
The present invention relates to a kind of technology of electrical distribution field, specifically a kind of MMC- based on unilateral transient current
HVDC transmission line fault detection method.
Background technology
Modular multilevel converter type HVDC (MMC-HVDC) transmission system has output quality of power supply height, the change of current
Device loss it is low, be easy to extension and system reliability it is high the advantages of, it has also become the main way of realization of flexible DC power transmission.It is flexible straight
Flow transmission line of electricity wide across region, fault rate is high, and excessively stream or overpressure problems are frequently accompanied by during failure generation, converter valve is made
Into impacting and influence the safety and stability of AC system.Compared with two level and three-level voltage source transverter, modular multilevel
Transverter (MMC) DC side is without bulky capacitor in parallel, AC line when causing the flexible direct current power transmission system DC side failure based on MMC
Road, fault branch and transverter form the fault loop of uniqueness, and fault characteristic and traditional two level and three level flexible direct currents are defeated
Electric system fault characteristic has notable difference.
The content of the invention
The present invention is directed to the following defect of prior art：DC voltage unbalance protection, DC minimum voltage protection and direct current mistake
Voltage protection is influenceed by capacitance type potential transformer transient response characteristic is poor, it is difficult to quick detection DC line fault；Directly
Stream overcurrent protection is only applicable to bipolar short-circuit low resistance faults, and can not realize the detection of monopolar grounding fault and disconnection fault；It is vertical
Connection current differential protection is easily influenceed by distribution capacity, it is necessary to prevent malfunction by being delayed, and responsiveness is slow, is used only as standby
Protection.Propose a kind of MMC-HVDC electric transmission line fault detection methods based on unilateral transient current.
The present invention is achieved by the following technical solutions：
The present invention relates to a kind of MMC-HVDC electric transmission line fault detection methods based on unilateral transient current, including it is following
Step：
1) electric current in DC line is sampled, when meeting DC line electric current update condition, updates DC line electricity
Flow valuve Idc；
2) carry out failure and there is judgement, work as Iop>IsetIWhen system there is failure and carry out next step, wherein：N1For the sampled point number in certain time window, k is last samples point, IsetIFor electricity
Flow setting valve；
3) DC line electric current natural mode of vibration Energy-Entropy H is calculated, there is event when meeting DC side failure criterion, i.e. DC side
Step 4 is performed during barrier, otherwise return to step 2.
4) Fault Identification criterion is built, according to Fault Identification criterion failure judgement type.
Described DC line electric current update condition isWherein：K is most
New sampled point, i (k) is current sampling data, and N is the sampled point number in certain time window.
For any one signal x (t), for time interval [t1,t2], described natural mode of vibration Energy-Entropy
Wherein：ci
(t) intrinsic mode function that is obtained after empirical mode decomposition is passed through for x (t)；rn(t) it is x (t) by after empirical mode decomposition
The residual error that arrives, x (t) empirical mode decomposition result is：
Described DC side failure criterion be min H (k) ..., H (k- (N2- 1) } ＞ Hset, wherein：N2For certain time window
Intraoral sampled point number, H (j) is time window [j- (N3- 1), j] interior DC current natural mode of vibration Energy-Entropy, N3For a timing
Between sampled point number in window, HsetFor natural mode of vibration Energy-Entropy threshold value.
Described Fault Identification criterion isWherein：M correspondences are protected
Startup time, i.e. t=mTsWhen Iop>IsetISet up for the first time, TsFor protection sampling period, Δ I (j)=IMAF(j)-Idc(j),N4For the sampled point number in certain time window, IsetIIFor current setting.
Technique effect
Compared with prior art, the present invention carries out failure using the good current signal transient of high-frequency signal progress of disease effect
Detection and classification, distinguish DC side and AC failure by natural mode of vibration Energy-Entropy, can be quickly detected DC side failure；
By moving average filter extraction curent change trend, fast response time, fault type recognition is accurately and reliably.
Brief description of the drawings
Fig. 1 is MMC-HVDC system structure diagrams；
Fig. 2 is schematic flow sheet of the present invention；
Fig. 3 is monopolar grounding fault schematic diagram；
Fig. 4 is bipolar short trouble schematic diagram；
Fig. 5 is disconnection fault schematic diagram；
Fig. 6 is the bipolar metallic short circuit fault protection figure in DC line midpoint；
Fig. 7 is DC line midpoint cathode metal earth-fault protection action diagram；
Fig. 8 is DC line midpoint positive pole disconnection fault protection act figure；
Fig. 9 is Inverter Station AC single phase metal ground protection action diagram.
Embodiment
As shown in figure 1, MMC-HVDC systems use symmetrical monopolar main wiring mode, DC side is through clamping resistance eutral grounding.f1、
f2And f3It is rectification side electric network fault position, inverter side electric network fault position, DC line fault position respectively.
During system dc line failure, fault traveling wave is produced at failure and is propagated to circuit both sides.Due to failure
Initial traveling wave includes different frequency component, while by the parameter frequency dependent characteristic of transmission line of electricity, traveling wave propagation distance, failure transition electricity
Electric current at the influence of the factor such as resistance and DC control, monitoring includes abundant high fdrequency component.Corresponding to DC side different type
Failure, specific features are as follows：DC line electric current generally steeply rises during bipolar short trouble, but is influenceed by fault traveling wave,
When fault distance is sufficiently large, short circuit current flow staged rises；During monopolar grounding fault, DC line electric current shakes through short duration high frequency
Recover after swinging normal；During disconnection fault, current conversion station normal power transmission in two ends is interrupted, and DC line electric current is through short duration high frequency
Zero is dropped to after vibration.
As shown in Fig. 2 MMC-HVDC electric transmission line fault detection methods comprise the following steps in the present embodiment：
1) electric current in DC line is sampled, when meeting DC line electric current update condition, updates DC line electricity
Flow valuve Idc.DC line electric current update condition isWherein：K is last samples
Point, i (k) is current sampling data, and N is the sampled point number in certain time window, and N takes adopting in 100ms time windows herein
Number of samples, IsetIFor current setting, I hereinsetI=0.01IN, INFor the specified running current of DC power transmission line.
2) carry out failure and there is judgement, work as Iop>IsetIWhen system there is failure and carry out next step, wherein：N1For the sampling number in 1ms time windows, k is last samples point, IsetIIt is whole for electric current
Definite value.
3) DC line electric current natural mode of vibration Energy-Entropy H is calculated, DC side has failure when meeting DC side failure criterion
And carry out next step.
Contain abundant fault message in voltage, current temporary state signal produced by fault transient, extract corresponding event
Hinder feature, quick, reliable relay protection can be achieved.Empirical mode decomposition (EMD) is a kind of by ripple of the signal by different scale
Dynamic or trend resolves into the signal processing method of limited intrinsic mode function (IMF) and a residual error step by step.EMD is according to number
Signal decomposition is adaptively completed according to the time scale feature of itself, without presetting any basic function.
Described natural mode of vibration Energy-Entropy combines empirical mode decomposition, signal energy and comentropy, natural mode of vibration Energy-EntropyWherein： ci(t) intrinsic mode function that is obtained after empirical mode decomposition is passed through for x (t)；rn(t) experience is passed through for x (t)
The residual error that is obtained after mode decomposition, x (t) empirical mode decomposition result is：Described DC side
Failure criterion be min H (k) ..., H (k- (N2- 1) } ＞ Hset, wherein：N2For the sampling number of 2ms time windows, HsetIt is solid
There is mode energy entropy threshold value.H (j) is time window [j- (N3- 1), j] in DC current natural mode of vibration Energy-Entropy, N3For
Sampling number in 5ms time windows, HsetFor natural mode of vibration Energy-Entropy threshold value, H hereinset=0.005.Meet DC side event
Barrier criterion then represents explanation DC line mode failure, now carries out step 4) determine whether fault type.
4) Fault Identification criterion is built, according to Fault Identification criterion failure judgement type.
Described Fault Identification criterion isWherein：M correspondences are protected
Startup time, i.e. t=mTsWhen Iop>IsetISet up for the first time, TsFor protection sampling period, Δ I (j)=IMAF(j)-Idc(j),IsetIIFor current setting, IsetII=0.1IN, INFor the specified running current of DC line, N4
For the sampled point number in 10ms time windows.By Fault Identification it is monopolar grounding fault, bipolar short according to Fault Identification criterion
Road failure or disconnection fault.
As seen in figures 3-5, if failure is bipolar short trouble, locking transverter and tripping AC circuit breaker.If single
When pole ground fault or disconnection fault, control strategy should be changed to reduce the influence to system and fix a breakdown as early as possible.
The present embodiment is based on system shown in Figure 1 and carries out simulating, verifying to the method for the invention.As shown in figure 1, system volume
Constant volume is 400MW, and DC rated voltage is 200kV, and DC power transmission line length is 200km.In emulation, reached surely with system
It is zero moment that timing, which is carved, and failure occurred at the 0.1s moment, and DC side trouble duration is 0.1s, AC trouble duration
For 0.05s.Data sampling frequency is 20kHz, and protection seting value is：N=2 000, N1=20, N2=40, N3=100, N4=
200、IsetI=0.01kA, IsetII=0.1kA, Hset=0.005.Simulation result is specific as Fig. 6 to Fig. 9, Fig. 6 to Fig. 8 show this
Method can reliably detect DC line fault and recognize fault type, Fig. 9 show this method in AC failure it is reliable not
Action.
Compared with prior art：The present invention carries out failure using the good current signal transient of high-frequency signal progress of disease effect
Detection and classification, distinguish DC side and AC failure by natural mode of vibration Energy-Entropy, can be quickly detected DC side failure；
By moving average filter extraction curent change trend, fast response time, fault type recognition is accurately and reliably.
Above-mentioned specific implementation can by those skilled in the art on the premise of without departing substantially from the principle of the invention and objective with difference
Mode local directed complete set is carried out to it, protection scope of the present invention is defined by claims and not by above-mentioned specific implementation institute
Limit, each implementation in the range of it is by the constraint of the present invention.
Claims (5)
1. a kind of MMC-HVDC electric transmission line fault detection methods based on unilateral transient current, it is characterised in that including following
Step：
1) electric current in DC line is sampled, when meeting DC line electric current update condition, updates DC line current value
Idc；
2) carry out failure and there is judgement, work as Iop>IsetIWhen system there is failure and carry out next step, wherein：N1For sampled point number, k is last samples point, IsetIFor current setting；
3) DC line electric current natural mode of vibration Energy-Entropy H is calculated, when meeting DC side failure criterion, i.e., when DC side has failure
Step 4 is performed, otherwise return to step 2；
4) Fault Identification criterion is built, according to Fault Identification criterion failure judgement type.
2. the MMC-HVDC electric transmission line fault detection methods according to claim 1 based on unilateral transient current, it is special
Levying is, described DC line electric current update condition isWherein：K is newest
Sampled point, i (k) is current sampling data, and N is sampled point number.
3. the MMC-HVDC electric transmission line fault detection methods according to claim 2 based on unilateral transient current, it is special
Levying is, described natural mode of vibration Energy-EntropyWherein：X (t) is any one signal, [t1,t2] it is time interval,For x
(t) intrinsic mode function by being obtained after empirical mode decomposition；rn(t) it is residual by what is obtained after empirical mode decomposition for x (t)
Poor item, x (t) empirical mode decomposition result is：
4. the MMC-HVDC electric transmission line fault detection methods according to claim 3 based on unilateral transient current, it is special
Levying is, described DC side failure criterion is min { H (k) ..., H (k- (N2- 1) } ＞ Hset, wherein：N2For certain time window
Interior sampled point number, H (j) is time window [j- (N3- 1), j] interior DC current natural mode of vibration Energy-Entropy, N3For certain time
Sampled point number in window, HsetFor natural mode of vibration Energy-Entropy threshold value.
5. the MMC-HVDC electric transmission line fault detection methods according to claim 4 based on unilateral transient current, it is special
Levying is, described Fault Identification criterion isWherein：M correspondence protections start
Moment, i.e. t=mTsWhen Iop>IsetISet up for the first time, TsFor protection sampling period, Δ I (j)=IMAF(j)-Idc(j),N4For the sampled point number in certain time window, IsetIIFor current setting.
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| CN108037409A (en) * | 2017-10-30 | 2018-05-15 | 中国电力科学研究院有限公司 | A kind of DC line fault detection method and device |
| CN109473956A (en) * | 2018-11-27 | 2019-03-15 | 西安交通大学 | Utilize the flexible direct current line one-end amount guard method of MMC type inverter characteristic frequency |
| CN110609215A (en) * | 2019-11-01 | 2019-12-24 | 云南电网有限责任公司电力科学研究院 | Flexible direct-current transmission line fault detection method and system based on transient current |
| CN110907753A (en) * | 2019-12-02 | 2020-03-24 | 昆明理工大学 | HHT energy entropy based MMC-HVDC system single-ended fault identification method |
| CN113381391A (en) * | 2021-05-21 | 2021-09-10 | 广西大学 | Novel single-end protection method for high-voltage direct-current transmission line |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN110609215A (en) * | 2019-11-01 | 2019-12-24 | 云南电网有限责任公司电力科学研究院 | Flexible direct-current transmission line fault detection method and system based on transient current |
| CN110907753A (en) * | 2019-12-02 | 2020-03-24 | 昆明理工大学 | HHT energy entropy based MMC-HVDC system single-ended fault identification method |
| CN110907753B (en) * | 2019-12-02 | 2021-07-13 | 昆明理工大学 | HHT energy entropy based MMC-HVDC system single-ended fault identification method |
| CN113381391A (en) * | 2021-05-21 | 2021-09-10 | 广西大学 | Novel single-end protection method for high-voltage direct-current transmission line |
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