CN107492871B - A kind of flexible direct current line direction longitudinal protection method based on total current amount - Google Patents
A kind of flexible direct current line direction longitudinal protection method based on total current amount Download PDFInfo
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- CN107492871B CN107492871B CN201710556622.6A CN201710556622A CN107492871B CN 107492871 B CN107492871 B CN 107492871B CN 201710556622 A CN201710556622 A CN 201710556622A CN 107492871 B CN107492871 B CN 107492871B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
- H02H7/268—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for dc systems
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H1/00—Details of emergency protective circuit arrangements
- H02H1/0007—Details of emergency protective circuit arrangements concerning the detecting means
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H1/00—Details of emergency protective circuit arrangements
- H02H1/0061—Details of emergency protective circuit arrangements concerning transmission of signals
- H02H1/0069—Details of emergency protective circuit arrangements concerning transmission of signals by means of light or heat rays
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
- H02H7/261—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured involving signal transmission between at least two stations
- H02H7/263—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured involving signal transmission between at least two stations involving transmissions of measured values
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- Emergency Protection Circuit Devices (AREA)
Abstract
The invention discloses a kind of flexible direct current line direction longitudinal protection method based on total current amount, the guard method is the following steps are included: step 1: a current sensor is respectively installed at by the breaker at protection DC line both ends；Step 2: being measured by current sensor respectively by the instantaneous value of protection DC line both ends electric current, and is utilized respectively total current amount and is differentiated sense of current；Step 3: being arranged protective device at two current sensors respectively, passes through fiber optic communication between protective device, and protective device differentiates to opposite end transmitting current direction as a result, the current direction for receiving opposite end simultaneously differentiates result；Step 4: when being simultaneously timing by the current direction at protection DC line both ends, it is determined as troubles inside the sample space, by the delay of protection exit, protection exit tripping；Step 5: according to troubles inside the sample space criterion formula, determining whether this route troubles inside the sample space, when criterion this route troubles inside the sample space meets, protection exit tripping.
Description
Technical field
The present invention relates to Relay Protection Technology in Power System fields, more particularly to the flexible direct current line based on total current amount
Road direction pilot protection method.
Background technique
With in the development of voltage source converter (voltage sourced converter, VSC) and power supply and load
The increase of DC link in current transformation, flexible direct current system due to its have control flexibly, convenient for receive distributed generation resource with
The advantages that DC load, power supply capacity are big, power quality is good has aroused extensive attention at home and abroad.However lack mature AC line
Road protection technique is one of the significant challenge that flexible direct current system faces.The difficult point of flexible direct current system route protection is should
Quickly identification DC Line Fault accurately selects faulty line to reduce scope of power outage again to prevent equipment damage in a short time.
Flexible direct current Line Current Differential Protection method includes: at present
1. Non-unit protection is difficult to realize clearly protect boundary, it is quick cannot preferably to meet flexible direct current route protection
Property and option demand.
2. influence of the current differential protection vulnerable to factors such as line distribution capacitance, mutual inductor saturation and measurement errors.
3. directional pilot protection has many advantages, such as that the traffic is small, is not necessarily to communication synchronization, but currently about DC line direction
The research of pilot protection is based primarily upon jump-value of current, and the control response speed of flexible direct current system is exceedingly fast, and VSC can after failure
Basic change occurs for the quick lock in 1ms, system topological, and principle of stacking will be no longer applicable in, it can be seen that being based on electric current
The directional pilot protection of Sudden Changing Rate is not suitable for flexible direct current system from principle.
Therefore, it is desirable to there is a kind of flexible direct current line direction longitudinal protection method based on total current amount that can overcome or extremely
Mitigate the problems of the prior art less.
Summary of the invention
The purpose of the present invention is to provide a kind of flexible direct current line direction longitudinal protection method pair based on total current amount
The failure process of entire flexible direct current route shields, and is not influenced by line distribution capacitance, and communication synchronization is not necessarily to.
The present invention provides a kind of flexible direct current line direction longitudinal protection method based on total current amount, including following step
It is rapid:
Step 1: a current sensor is respectively installed at by the breaker at protection flexible direct current route both ends；
Step 2: being measured by current sensor respectively by the instantaneous value of protection flexible direct current route both ends electric current, and point
Not Li Yong total current amount differentiate sense of current, criterion are as follows:
I in formulapAnd inIt is the instantaneous value of positive electrode current and cathodal current respectively；IsetIt is a positive number for preset threshold,
If criterion meets, then it is assumed that sense of current is positive；
Step 3: protective device is set at two current sensors respectively, passes through fiber optic communication, guarantor between protective device
Protection unit differentiates to opposite end transmitting current direction as a result, the current direction for receiving opposite end simultaneously differentiates result；
Step 4: when being simultaneously timing by the current direction at protection flexible direct current route both ends, it is determined as troubles inside the sample space, passes through
The delay of overprotection outlet, protection exit tripping.
Preferably, current sensor in the step 1 realizes wide frequency domain linear transform, and installation polarity is electric current from mother
Line direction is described to be positive by protection flexible direct current route.
Preferably, the protective device in the step 3 is relay protector.
Preferably, under bipolar short-circuit conditions, there are direction characters for the total current amount of fault current: positive electrode current is from the change of current
Device flows to fault point, and cathodal current flows to inverter from fault point, and the step 4 utilizes the direction character of total current amount, determines
Troubles inside the sample space.
Preferably, the maximum communication that the protection exit delay is greater than the protective device is delayed.
The invention discloses a kind of flexible direct current line direction longitudinal protection method based on total current amount, through the invention
The flexible direct current line direction longitudinal protection method based on total current amount need to only acquire route both ends current information, be not necessarily to voltage
Sampling, this method after by converter blocking topology it is not changed influence, can shield to entire failure process, not by
The influence of line distribution capacitance is not necessarily to communication synchronization.
Detailed description of the invention
Current direction schematic diagram when Fig. 1 is two level VSC bipolar short trouble；
Fig. 2 is the work flow diagram of the flexible direct current line direction longitudinal protection method based on total current amount；
Fig. 3 is the protection point schematic diagram of the flexible direct current line direction pilot protection system based on total current amount；
Route both ends current waveform figure when Fig. 4 is troubles inside the sample space；
Route both ends current waveform figure when Fig. 5 is external area error；
Route both ends current waveform figure when Fig. 6 is load fluctuation.
Specific embodiment
To keep the purposes, technical schemes and advantages of the invention implemented clearer, below in conjunction in the embodiment of the present invention
Attached drawing, technical solution in the embodiment of the present invention is further described in more detail.In the accompanying drawings, identical from beginning to end or class
As label indicate same or similar element or element with the same or similar functions.Described embodiment is the present invention
A part of the embodiment, instead of all the embodiments.The embodiments described below with reference to the accompanying drawings are exemplary, it is intended to use
It is of the invention in explaining, and be not considered as limiting the invention.Based on the embodiments of the present invention, ordinary skill people
Member's every other embodiment obtained without creative efforts, shall fall within the protection scope of the present invention.Under
Face is described in detail the embodiment of the present invention in conjunction with attached drawing.
As shown in Figure 1, bipolar fault progression process can be divided into three phases: capacitor discharge regime, diode are freely connected
Stage with exchange the side feed-in stage.
Capacitor discharge regime, fault current mainly include the discharge current of shunt capacitor, equivalent circuit such as Fig. 1 (a)
It is shown.The expression formula of this stage fault current are as follows:
In formula, ifFor positive fault current, vCFor shunt capacitor both end voltage；V0For failure initial time voltage, ω is
The oscillation angular frequency of electric current, ω0For the resonance angular frequency of capacitor discharging circuit, β is the oscillation phase angle difference of voltage and current；R and L
Respectively line resistance and inductance.
From above formula it is found that when ω t is at [0, π], fault current ifIt is positive；When ω t is greater than π-β, capacitance voltage vCIt will be by
Just becoming negative.Significantly, since the presence of anti-parallel diodes, shunt capacitor will not be reversed charging, electricity
Pressure is not in negative value.I.e. when ω t be equal to π-β when, capacitor discharge regime will terminate, fault current can by diode continuousing flow,
Failure enters the free conducting phase of diode.Therefore, in capacitor discharge regime, the direction of fault current are as follows: positive route flow direction
Fault point, anode circuit outgoing failure point.
The free conducting phase of diode, shown in equivalent circuit such as Fig. 1 (b), the expression formula of fault current are as follows:
if=I '0e-(R/L)t (2)
I in formula0ˊ is the fault current at the end of capacitor discharge regime, the i.e. fault current at (π-β)/ω moment, therefore I0ˊ
For the positive value greater than 0.Therefore, in the free conducting phase of diode, the direction of fault current is still: positive route flows to failure
Point, anode circuit outgoing failure point.
The side feed-in stage is exchanged, AC power source passes through diode rectifier bridge (inverter after locking) to fault point feed-in event
Hinder the process of electric current, shown in equivalent circuit such as Fig. 1 (c).It is dominated by exchanging side feed-in electric current in fault current direction.Due to two poles
The conducting of pipe has directionality, therefore in the exchange side feed-in stage, fault current direction is still are as follows: and positive route flows to fault point,
Anode circuit outgoing failure point.
In conclusion bipolar short trouble occurs for flexible direct current system, the electric current of three failure phases after converter blocking
Directional characteristic has consistent conclusion, i.e., in its entire failure process, the direction of fault current is positive route flow direction always
Fault point, anode circuit outgoing failure point.
For MMC, failure process only includes capacitor discharge regime and exchange feed-in stage, the side of fault current
It is consistent with above-mentioned analysis to feature.
Therefore either two level VSC or MMC, under bipolar short-circuit conditions, electric current there are certain direction character,
Using this direction character, the invention proposes the direction pilot line protection methods based on total current amount.
As shown in Figures 2 and 3, the workflow of guard method includes the following steps:
Step 11: current sensor being installed at flexible direct current route both ends, measures the current instantaneous value of DC line；
Step 12: current instantaneous value being compared with preset threshold value, the direction of Cutoff current.Its criterion are as follows:
I in formulapAnd inIt is the instantaneous value of positive electrode current and cathodal current respectively；InFor the load current value of institute's protection circuit,
It is a positive number.If criterion meets, then it is assumed that sense of current is positive；
Step 13: as shown in figure 3, protective device differentiates to opposite end transmitting current direction as a result, simultaneously by fiber optic communication
The current direction for receiving opposite end differentiates result；
Step 14: when the current direction at both ends is simultaneously timing, can determine that as troubles inside the sample space, by centainly exporting delay,
Protection exit tripping.For the route within 20km, the settable 0.3ms of outlet delay.
The test result for ± 10kV the flexible direct current system that the present invention is built on PSCAD/EMTDC is given below.
As shown in figure 4, when troubles inside the sample space, the positive electrode current rapid mutation of the side M and the side N to 0.2In or more, cathodal current is fast
Speed mutation is to -0.2In hereinafter, protection can be exported quickly.
As shown in figure 5, when external area error, the positive electrode current of the side N always in 0.2In hereinafter, the cathodal current of the side N always
More than -0.2In, therefore the positive direction criterion of the side N is unsatisfactory for, and directional pilot protection all will not malfunction.
As shown in fig. 6, the positive electrode current of the side N is always in 0.2In hereinafter, the cathodal current of the side N when load fluctuation occurs
Always more than -0.2In, therefore the positive direction criterion of the side N is unsatisfactory for, and directional pilot protection all will not malfunction.
As it can be seen that present invention protection has good reliability, rapidity and selectivity.
Finally it is noted that the above embodiments are merely illustrative of the technical solutions of the present invention, rather than its limitations.To the greatest extent
Present invention has been described in detail with reference to the aforementioned embodiments for pipe, those skilled in the art should understand that: it is still
It is possible to modify the technical solutions described in the foregoing embodiments, or part of technical characteristic is equally replaced
It changes；And these are modified or replaceed, the essence for technical solution of various embodiments of the present invention that it does not separate the essence of the corresponding technical solution
Mind and range.
Claims (5)
1. a kind of flexible direct current line direction longitudinal protection method based on total current amount, which comprises the following steps:
Step 1: a current sensor is respectively installed at by the breaker at protection flexible direct current route both ends；
Step 2: being measured by current sensor respectively by the instantaneous value of protection flexible direct current route both ends electric current, and benefit respectively
Sense of current, criterion are differentiated with total current amount are as follows:
I in formulapAnd inIt is the instantaneous value of positive electrode current and cathodal current respectively；IsetIt is a positive number for preset threshold, if
Criterion meets, then it is assumed that sense of current is positive；
Step 3: protective device is set at two current sensors respectively, passes through fiber optic communication, protection dress between protective device
It sets to opposite end transmitting current direction and differentiates as a result, the current direction for receiving opposite end simultaneously differentiates result；
Step 4: when being simultaneously timing by the current direction at protection flexible direct current route both ends, it is determined as troubles inside the sample space, by protecting
Protect the delay of outlet, protection exit tripping.
2. the flexible direct current line direction longitudinal protection method based on total current amount as described in claim 1, it is characterised in that:
Current sensor in the step 1 realizes wide frequency domain linear transform, and installation polarity is that electric current is protected from bus direction is described
Flexible direct current route is positive.
3. the flexible direct current line direction longitudinal protection method based on total current amount as described in claim 1, it is characterised in that:
Protective device in the step 3 is relay protector.
4. the flexible direct current line direction longitudinal protection method based on total current amount as described in claim 1, it is characterised in that:
Under bipolar short-circuit conditions, there are direction characters for the total current amount of fault current: positive electrode current flows to fault point from inverter, bears
Electrode current flows to inverter from fault point, and the step 4 utilizes the direction character of total current amount, determines troubles inside the sample space.
5. the flexible direct current line direction longitudinal protection method based on total current amount as claimed in claim 4, it is characterised in that:
The maximum communication that the protection exit delay is greater than the protective device is delayed.
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| CN107492871B true CN107492871B (en) | 2019-01-15 |
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| CN109546677B (en) * | 2018-11-07 | 2020-06-23 | 国网浙江省电力有限公司经济技术研究院 | Safety control strategy solving method for large-scale offshore wind power flexible sending-out system |
| CN109839575B (en) * | 2019-04-04 | 2021-07-06 | 国家电网有限公司 | Power system fault processing method and device and terminal equipment |
| CN110350500B (en) * | 2019-08-13 | 2021-08-27 | 南京南瑞继保电气有限公司 | Method, device, system, equipment and medium for protecting pseudo bipolar direct current distribution network |
| CN111614067A (en) * | 2020-06-08 | 2020-09-01 | 广州市扬新技术研究有限责任公司 | Direct current traction pilot protection system and method based on optical fiber communication |
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|---|---|---|---|---|
| WO1993016517A1 (en) * | 1992-02-12 | 1993-08-19 | Asea Brown Boveri Ab | Method and device for preventing overstabilization of longitudinal differential protection in case of internal fault |
| CN102510050A (en) * | 2011-11-08 | 2012-06-20 | 西安交通大学 | Pilot protection method for direct current line current abrupt change of multi-terminal direct current transmission system |
| CN106058828A (en) * | 2016-07-18 | 2016-10-26 | 天津大学 | Multi-terminal flexible DC power grid line direction pilot protection method |
| CN106711971A (en) * | 2017-02-09 | 2017-05-24 | 东南大学 | Method for protecting double-end direct current distribution network |
-
2017
- 2017-07-10 CN CN201710556622.6A patent/CN107492871B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1993016517A1 (en) * | 1992-02-12 | 1993-08-19 | Asea Brown Boveri Ab | Method and device for preventing overstabilization of longitudinal differential protection in case of internal fault |
| CN102510050A (en) * | 2011-11-08 | 2012-06-20 | 西安交通大学 | Pilot protection method for direct current line current abrupt change of multi-terminal direct current transmission system |
| CN106058828A (en) * | 2016-07-18 | 2016-10-26 | 天津大学 | Multi-terminal flexible DC power grid line direction pilot protection method |
| CN106711971A (en) * | 2017-02-09 | 2017-05-24 | 东南大学 | Method for protecting double-end direct current distribution network |
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