Specific embodiment
With reference to the attached drawing in the embodiment of the present invention, technical solution in the embodiment of the present invention carries out clear, complete
Ground description, it is clear that described embodiments are only a part of the embodiments of the present invention, instead of all the embodiments.Based on this
The embodiment of invention, every other implementation obtained by those of ordinary skill in the art without making creative efforts
Example, belongs to protection scope of the present invention.
The embodiment of the present invention is described in further detail below in conjunction with attached drawing, is implemented as shown in Figure 1 for the present invention
The method flow schematic diagram for the new energy station multiterminal pilot protection based on cosine similarity that example provides, which comprises
Step 1, for by the grid-connected new energy station of power electronics inverter, in conjunction with the common negative-sequence current that inhibits
Control strategy obtains the transient short circuit current analytic expression of new energy station failure;
The detailed process of the step are as follows:
Firstly, new energy station grid-connected inverters loop equation indicates under dq coordinate system are as follows:
In formula, L is the equivalent inductance of grid-connected inverters topology;R is the substitutional resistance of grid-connected inverters topology;idFor dq seat
D shaft current under mark system;iqFor the q shaft current under dq coordinate system;udFor the d shaft voltage of inverter outlet;uqFor inverter outlet
Q shaft voltage;edFor power grid electromotive force d axis component;eqFor power grid electromotive force q axis component;ω is angular frequency;
When above-mentioned new energy station inverter uses voltage-to-current double-closed-loop control device, in the control for inhibiting negative-sequence current
Under strategy, the governing equation of inverter be can be written as:
In formula, kip、kiiIt is current regulator ratio, integration time constant respectively;Respectively indicate d shaft current ginseng
Examine value and q shaft current reference value;id, iqRespectively indicate d axis, q shaft current actual value;L is the equivalence electricity of grid-connected inverters topology
Sense;edFor power grid electromotive force d axis component;eqFor power grid electromotive force q axis component.
It will disconnect outer voltage when inverter transient response, at this moment dq shaft current is mainly influenced by current control inner ring, PI
Electric current loop only needs to track given reference value, can in conjunction with the loop equation and inverter control equation of grid-connected inverters
To obtain inverter transient response equation are as follows:
In formula, kip、kiiIt is current regulator ratio, integration time constant respectively;Respectively indicate the reference of d shaft current
Value and q shaft current reference value;id, iqRespectively indicate d axis, q shaft current actual value;L is the equivalent inductance of grid-connected inverters topology.
When due to operating normally, new energy station generally keeps rated power factor to run, so dq axis initial current id0
=1p.u., iq0=0p.u. solves the transient current analytic expression under the available dq axis of inverter transient response equation are as follows:
Wherein, id, iqRespectively indicate d axis, q shaft current actual value;Respectively indicate d shaft current reference value and q axis electricity
Flow reference value;ξ is the damping ratio of second-order system, and value isωnAngular frequency, value are vibrated naturally for second-order system
ForωdDamped oscillation frequency is represented, value isβ is drag angle, and value is
It is short that the transient current analytic expression is further converted to by the new energy station under ABC coordinate system by coordinate transform
Road electric current analytic expression, is embodied as:
Wherein, iφFor the short circuit current of phase any in three-phase;θφInitial phase angle after representing three-phase fault;ω represents lock
The angular frequency that phase ring detects;t0For failure start time.
Step 2, according to the new energy station short circuit current analytic expression, analysis obtains new energy station short circuit current waveform
In the characteristic that the sine wave that non-power frequency decays is superimposed with non-power frequency sine wave, and thus construct the new energy based on cosine similarity
Source station multiterminal pilot protection criterion;
In the step, the short circuit current analytic expression of conventional synchronization power supply is indicated are as follows:
In formula, i is the short circuit current of any phase in three-phase;Eq|0|And xdRespectively synchronous machine built-in potential and synchronous electricity
It is anti-;x″dWith x 'd、T″dWith T 'dSynchronous machine reactance, AC compounent damping time constant in respectively secondary transient state and transient process;
ω is power frequency angular frequency;TaIt is DC component damping time constant;For fault initial angle.
According to above formula it is found that conventional synchronization power supply short circuit current waveform shows as the power frequency exponentially to decay sine
Wave;And the characteristic that the sine wave of non-power frequency decaying is superimposed with non-power frequency sine wave is presented in new energy station short circuit current waveform.This
There are huge differences for two kinds of characteristics, and the new energy station multiterminal based on cosine similarity can be constructed using this species diversity
Pilot protection criterion, specifically:
Line topological is sent out in conjunction with new energy station T direct type, it is synchronous that all T are connect the long internal clock of new energy station 10ms window
Current sampling data it is corresponding be added, operation result is denoted as station side and current vector
In formula, N, which is represented, shares N number of new energy station access on T direct type submitting route;iwkFor k-th of new energy station
The synchronous current sampling data vector of the long internal clock of 10ms window;N is the total number of all sampled points in 10ms window is long;
The synchronous current sampling data of the long internal clock of synchronization system side 10ms window is denoted as system side current vector, indicates are as follows: is
=(is1,is2,…,isn);
Above-mentioned two current vector is substituted into following cosine similarity formula and is calculated again:
In formula, cos (iw,is) represent two current vectors cosine similarity calculate;
Wherein, when external area error occurs, the transient current waveform of station side and electric current and system side electric current is on the contrary, calculate
Obtain two current vector coefficient of similarity cos (iw,is)=- 1;When troubles inside the sample space occurs, since new energy power supply and tradition are same
It is different to walk power failure characteristic, two sides transient current wave-form similarity is poor, and the coefficient of similarity being calculated will be greater than -1;By
It being directly grounded in the neutral point of main transformer in wind-powered electricity generation station, when ground fault occurring in area, zero-sequence current is larger in system, so that
Thus the calculated value of cosine similarity constructs the new energy station multiterminal pilot protection based on cosine similarity and sentences near 1
According to expression are as follows:
cos(iwΣ,is) > cosset
In formula, subscript φ is any phase in ABC three-phase, calculates coefficient of similarity using the data of same famous prime minister;cossetFor
Definite value is protected, value range is between [- 1,1].
Step 3, angular error when being operated normally according to system and amplitude error are in the multiterminal pilot protection criterion
Protection definite value adjusted.
Here, the protection definite value in the multiterminal pilot protection criterion is carried out adjusting used formula are as follows:
Wherein, K is safety factor;KangFor angular error coefficient;KampFor amplitude error coefficient;KmarFor nargin coefficient;
cossetTo protect definite value.
For example, angular error is mainly derived from pilot protection communication synchronization error and CT angular error, chooses electric current
Reference direction is that bus is directed toward route, in the case where not considering angular error, station side and electric current and system side current waveform
Completely on the contrary, cosine similarity calculated value is -1 at this time.In view of synchronous error is up to 0.5ms, corresponding 9 ° of power frequency angle;CT
Angular error is generally considered as 7 °, so angular error is 16 ° total.When angular error is 16 °, corresponding cosine similarity is calculated
Value is -0.960, and in order to escape angular error, the COEFFICIENT K about angular error is arrangedang。
Other than angular error, amplitude error also will affect cosine similarity calculated value, be mainly derived from CT amplitude mistake
Difference.Since CT precision is generally 5% or 10%, under 10% amplitude error, cosine similarity calculated value is -0.993.In order to hide
Amplitude error is crossed, the COEFFICIENT K about amplitude error is setamp。
In addition, under normal circumstances protection definite value setting in order to ensure reliability need to there are certain nargin, so setting about
The COEFFICIENT K of narginmar。
Such as can choose that angular error coefficient is 0.95, amplitude error coefficient is 0.99, nargin coefficient is 0.95, it calculates
Obtaining safety factor K is 0.9, it is possible thereby to know that the setting valve of protection definite value is cosset=-1 × 0.9=-0.9.
It is described in detail below with process of the specific example to the above method, is illustrated in figure 2 the present invention and lifts in fact
Scale new energy station T direct type sends out line topological and abort situation schematic diagram, a power electronics unit table in Fig. 2 in example
Show a new energy station (general rated capacity is 50MW or 100MW), multiple new energy fields can be connect with T on a submitting route
It stands, is then incorporated to external sync system through overhead line, the T direct type that voltage class is 220kV in Fig. 2, which is sent out, accesses two on route
100MW new energy station, wherein #1 new energy station is permanent magnetism wind power plant, and single machine rated capacity is 1.5MW, shares 99 typhoons
Machine, set end voltage 0.69kV;#2 new energy station is double-fed fan motor field, and single machine rated capacity is 3MW, totally 33 Fans, machine
End voltage is 0.69kV;Case becomes rated capacity 3.5MVA, no-load voltage ratio 35kV/0.69kV, Dyn wiring, short-circuit impedance 6.76%;It is equivalent
Collect 0.11 Ω of line resistance, 409.5 μ H of inductance.Main transformer rated capacity 120MVA, no-load voltage ratio 220kV/35kV, YNd wiring, short circuit resistance
Anti- 6%.Route overall length 40km is sent out, positive and negative sequence impedance is 0.076+j0.338 Ω/km, zero sequence impedance 0.284+
J0.824 Ω/km, T contact is located at route midpoint.Topological structure and above-mentioned parameter according to fig. 2 is in Real Time Digital Simulator
New energy T is built in (Real time digital simulator, RTDS) connects grid-connected system electrical-magnetic model to verify this
Invent the method proposed.
Abort situation at totally 6, is separately positioned on and sends out route W1、W2, the side S is externally ported and inner proximal, be denoted as respectively
K11,K12,K13,K14,K15,K16.Fault type includes all 4 seed types, including the event of singlephase earth fault, two phase ground
Barrier, two-phase short-circuit fault, three phase short circuit fault are grounded respectively with A phase, BC two phase ground, BC line to line fault and ABC three-phase shortcircuit
For, above 4 kinds of fault types are abbreviated as AG, BCG, BC, ABC respectively.
It is illustrated in figure 3 new energy station T direct type in example of the present invention and sends out circuit relay protection device and connect and show
It is intended to.It is as shown in Figure 3: to send out route W1Side, W2Side and the side S are mounted with protective relaying device W respectively1、W2And S, every suit protection
Device independently measures this side three-phase current, and the sampled value of other two sides is obtained by communication channel.It proposes through the invention
The new energy station multiterminal pilot protection criterion based on cosine similarity, utilize same famous prime minister station side and electric current and system side electricity
It flows sampled value and carries out cosine similarity calculating, judge abort situation and send out trip signal to corresponding breaker.
It is illustrated in figure 4 in example of the present invention T junction in area and protection act situation when A phase ground fault occurs
(troubles inside the sample space);It is illustrated in figure 5 in example of the present invention T junction in area and protection act when BC two-phase short-circuit fault occurs
Situation (troubles inside the sample space);It is illustrated in figure 6 in example of the present invention T junction in area and protection when BC double earthfault occurs
Action situation (troubles inside the sample space);It is illustrated in figure 7 in example of the present invention T junction in area and guarantor when ABC three-phase fault occurs
It protects action situation (troubles inside the sample space).Wherein solid line is A phase cosine similarity calculated value, and dotted line is B phase cosine similarity calculated value,
Chain-dotted line is C phase cosine similarity calculated value;In order to clearly illustrate Perfomance of protective relaying, it is fixed that protection has been marked with double dot dash line
Value.0ms is that the moment occurs for failure in figure, and the cosine similarity coefficient calculated value of the 5ms after troubles inside the sample space, failure phase are just more than
Definite value -0.9 is protected, and cosine similarity calculated value tends towards stability in 10~15ms, protection reliably, can be identified rapidly
Area's internal and external fault, and act in circuit breaker trip.
It is former for different faults position shown in Fig. 2, difference for the validity for further verifying the proposed method of the present invention
A large amount of simulation studies are carried out situations such as hindering type in Real Time Digital Simulator (RTDS), the following table 1 gives all emulation knots
Fruit, cosine similarity in 20ms after " cosine similarity index variation range " is referred to from failure start time to failure in table 1
The variation range of coefficient;In the case that table 2 gives T junction through transition resistive short, the action performance of protection.In table 2
" cosine similarity calculated value " is the cosine similarity being calculated using all sampled values in failure the latter data window length;
When the new energy station T direct type that table 3 gives different capabilities is sent out, the cosine similarity calculated value of T junction failure.In table 3
" cosine similarity calculated value " be using failure the latter data window it is long in the cosine that is calculated of all sampled values it is similar
Degree.
Table 1
Table 2
Table 3
Above-mentioned simulation result shows that protection reliably can rapidly identify various types of area's internal and external faults, troubles inside the sample space
10~15ms protects cosine similarity calculated value to be greater than protection definite value -0.9 and tends towards stability afterwards, and protection quick-action is good;Protection
It is not influenced by new energy station capacity and the method for operation, can guarantee higher sensitivity in various situations;It is short through transition resistance
In the case where road, protection still has reliability, is resistant to high resistive fault.
It is worth noting that, the content being not described in detail in the embodiment of the present invention belongs to professional and technical personnel in the field's public affairs
The prior art known.
In conclusion traditional protection sensitivity decline is even refused when the method for the embodiment of the present invention avoids troubles inside the sample space
Dynamic situation, while when sending out route troubles inside the sample space, protection can action message, and can be realized complete fibre;This method is not
It is influenced by new energy power supply capacity, the method for operation, and uncontrolled strategy influences.
The foregoing is only a preferred embodiment of the present invention, but scope of protection of the present invention is not limited thereto,
Within the technical scope of the present disclosure, any changes or substitutions that can be easily thought of by anyone skilled in the art,
It should be covered by the protection scope of the present invention.Therefore, protection scope of the present invention should be with the protection model of claims
Subject to enclosing.