CN112165114B - Alternating current-direct current hybrid system transient stability analysis method considering commutation failure - Google Patents
Alternating current-direct current hybrid system transient stability analysis method considering commutation failure Download PDFInfo
- Publication number
- CN112165114B CN112165114B CN202011083828.XA CN202011083828A CN112165114B CN 112165114 B CN112165114 B CN 112165114B CN 202011083828 A CN202011083828 A CN 202011083828A CN 112165114 B CN112165114 B CN 112165114B
- Authority
- CN
- China
- Prior art keywords
- direct current
- transient
- fault
- alternating current
- hybrid system
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
- H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Supply And Distribution Of Alternating Current (AREA)
Abstract
The invention discloses an alternating current-direct current hybrid system transient stability analysis method considering commutation failure, aiming at an alternating current-direct current hybrid system of a high-voltage direct current transmission line containing a power grid commutation type, establishing a network structure maintenance model of the alternating current-direct current hybrid system by equivalently using a direct current converter station as a dynamic load on a corresponding converter bus, and constructing an energy function of the alternating current-direct current hybrid system through first integration; secondly, a trapezoidal integral path is adopted to approximately calculate a transient energy function of the system after the fault, a transient stability criterion based on the energy function is provided, and meanwhile, the dichotomy is utilized to quickly calculate the limit removal time of the system; and finally, an improved IEEE-39 node alternating current-direct current hybrid system is built, and the correctness of the theoretical analysis method is verified through simulation. When the alternating current-direct current hybrid system fails in an alternating current system and causes phase commutation failure on the inversion side of a direct current line, transient stability margin analysis can be rapidly carried out.
Description
Technical Field
The invention relates to an alternating current and direct current hybrid system transient stability analysis technology, in particular to an alternating current and direct current hybrid system transient stability analysis method considering commutation failure.
Background
At present, large primary energy bases and load centers are generally distributed in a reverse direction. In order to optimize resource allocation and improve energy utilization efficiency, a Line Commutated Converter High Voltage Direct Current (LCC-HVDC) Converter type High Voltage Direct Current (LCC-HVDC) power transmission is rapidly developed by virtue of advantages in the aspects of long-distance and large-capacity power transmission and the like. The alternating current-direct current hybrid system has the characteristics of high direct current occupation ratio and large capacity on a power grid structure. When an alternating current system in the near area of a converter station at the inversion side of a direct current line fails, the phase change failure at the inversion side of the direct current is caused at the same time, so that the short-time large-range transfer of the power flow is caused, and the safe and stable operation of the system is seriously threatened. Alternating current side faults in the alternating current-direct current hybrid system and direct current line commutation failure are accompanied, transient stability of the system is greatly influenced, and on-line transient stability analysis of the alternating current-direct current hybrid system containing LCC-HVDC is necessary to be studied deeply.
In the field of transient stability analysis of alternating current and direct current hybrid systems, a great deal of research has been carried out by domestic and foreign scholars. Compared with a time domain simulation method, the energy function method judges the transient stability of the system from the energy perspective, can give the stability margin of the system and determine the instability trend of the system, and is widely applied to the transient stability analysis of the power system. Ni and Fouaad define corresponding transient energy functions by neglecting dynamic processes of direct current lines and control and adopting a quasi-steady state direct current model for the first time, and direct transient stability analysis is realized by utilizing a RUEP method.
In the prior art, n.fernandopulle and r.t.h.alden, "integration of cascaded HVDC dynamics in transient energy functions," IEEE trans.power system ", vol.20, No.2, pp.1043-1052, and may.2005, a differential equation is introduced to characterize the dynamic characteristics of HVDC when a transient energy function is constructed, so that the prediction accuracy of the transient stability of the alternating current/direct current hybrid system is improved, and the calculation time is also saved.
In the second prior art, based on a network structure maintenance Model, a transient Energy Function considering Detailed dynamic characteristics of a direct current line is constructed, and a numerical algorithm for constructing the Energy Function is provided, wherein the "Energy Function for Power System with Detailed DC Model" Construction and Analysis, "IEEE trans.
The existing technology has the disadvantages that when an alternating current system of the alternating current-direct current hybrid system fails and causes a phase commutation failure on an inversion side of a direct current line, the transient stability of the system is seriously impacted, and a fast transient stability margin analysis method under the current scene has few literature reports.
Disclosure of Invention
The invention aims to provide an alternating current-direct current hybrid system transient stability analysis method considering commutation failure.
The purpose of the invention is realized by the following technical scheme:
the invention discloses an alternating current-direct current hybrid system transient stability analysis method considering commutation failure, which aims at an alternating current-direct current hybrid system of a high-voltage direct current transmission line containing a power grid commutation type, constructs a transient energy function containing a direct current line, and carries out transient stability analysis on the alternating current-direct current hybrid system under the scene of commutation failure on a direct current inversion side caused by an alternating current fault, and comprises the following steps:
firstly, establishing a network structure maintenance model of an alternating current-direct current hybrid system by equivalently using a direct current convertor station as a dynamic load on a corresponding convertor bus, and constructing an energy function of the alternating current-direct current hybrid system through first integration;
secondly, a trapezoidal integral path is adopted to approximately calculate a transient energy function of the system after the fault, a transient stability criterion based on the energy function is provided, and meanwhile, the dichotomy is utilized to quickly calculate the limit cut-off time of the system;
and finally, an improved IEEE-39 node alternating current-direct current hybrid system is built, and the correctness of the theoretical analysis method is verified through simulation.
According to the technical scheme provided by the invention, the transient stability analysis method of the alternating current-direct current hybrid system considering the commutation failure provided by the embodiment of the invention can be used for quickly analyzing the transient stability margin under the condition that the alternating current-direct current hybrid system fails and causes the commutation failure on the inversion side of the direct current line.
Drawings
FIG. 1 is a schematic diagram of a model of an AC/DC hybrid system according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of an equivalent model of a converter station in an embodiment of the invention;
FIG. 3 is a schematic diagram of a CEPRI-7 AC/DC system model according to an embodiment of the present invention;
FIG. 4 is a diagram illustrating a critical stability scenario in an embodiment of the present invention; in the figure: (a) gamma curve of turn-off angle, (b) Pd curve of direct current power, (c) theta curve of relative rotor angle, (d) mu ray A curve;
FIG. 5 is a schematic diagram of an unstable scenario in an embodiment of the present invention; in the figure: (a) gamma curve of turn-off angle, (b) Pd curve of direct current power, (c) theta curve of relative rotor angle, and (d) mu ray A curve;
FIG. 6 is a schematic diagram illustrating a transient stability margin evaluation process according to an embodiment of the invention;
FIG. 7 is a schematic diagram of an improved IEEE-39 AC/DC hybrid system in an embodiment of the present invention;
FIG. 8 is a schematic diagram illustrating a stable equilibrium point unchanged in a stable scene according to an embodiment of the present invention; in the figure: (a) gamma curve of turn-off angle, (b) theta curve of relative rotor angle, (c) V curve of energy function, and (d) mu ray A curve;
FIG. 9 is a schematic diagram illustrating a stable equilibrium point unchanged under an unstable scenario in an embodiment of the present invention; in the figure: (a) gamma curve of turn-off angle, (b) theta curve of relative rotor angle, (c) V curve of energy function, and (d) mu ray A curve;
FIG. 10 is a schematic diagram illustrating a stable equilibrium point change in a stable scene according to an embodiment of the present invention; in the figure: (a) gamma curve of turn-off angle, (b) theta curve of relative rotor angle, (c) V curve of energy function, and (d) mu ray A curve;
FIG. 11 is a schematic diagram illustrating a stable equilibrium point change in an unstable scenario according to an embodiment of the present invention; in the figure: (a) gamma curve of turn-off angle, (b) theta curve of relative rotor angle, (c) V curve of energy function, and (d) mu ray A curve.
Detailed Description
The embodiments of the present invention will be described in further detail below. Details which are not described in detail in the embodiments of the invention belong to the prior art which is known to the person skilled in the art.
The invention relates to an alternating current-direct current hybrid system transient stability analysis method considering commutation failure, which has the preferred specific implementation mode that:
to containing electric wire netting commutation type high voltage direct current transmission line's alternating current-direct current series-parallel connection system, construct the transient state energy function that contains the direct current circuit, under alternating current fault causes the direct current contravariant side and takes place commutation failure scene, carry out transient state stability analysis to alternating current-direct current series-parallel connection system, include:
firstly, establishing a network structure maintenance model of an alternating current-direct current hybrid system by equivalently using a direct current convertor station as a dynamic load on a corresponding convertor bus, and constructing an energy function of the alternating current-direct current hybrid system through first integration;
secondly, a trapezoidal integral path is adopted to approximately calculate a transient energy function of the system after the fault, a transient stability criterion based on the energy function is provided, and meanwhile, the dichotomy is utilized to quickly calculate the limit cut-off time of the system;
and finally, an improved IEEE-39 node alternating current-direct current hybrid system is built, and the correctness of the theoretical analysis method is verified through simulation.
The method specifically comprises the following steps:
step 1: constructing a network structure maintenance model of the AC-DC hybrid system:
for an alternating current-direct current hybrid system with n nodes and l direct current lines (LCC-HVDC), wherein i is 1,2, the node is connected with a generator, the synchronous generator adopts E' q constant representation, the voltage characteristic of a load is considered, the resistance of the high voltage line is ignored, two ends of the direct current lines are equivalent to the injection power of the corresponding bus, and an equivalent model based on a system network structure holding model is obtained;
in the inertial Center (COI) reference coordinate, the system equation is:
1) characteristic equation of synchronous generator
In the formula: 1,2, ·, m; theta i and omega i are respectively the power angle and the angular speed of the ith synchronous generator relative to an inertia Center (COI); ui and phi i are respectively the amplitude and phase angle of the ith node; pmi, Pei and Di are respectively the mechanical input power, active power output and damping of the ith generator; mi and PCOI are respectively an inertia time constant and an acceleration power of an inertia Center (COI) of the ith synchronous generator;
2) load equation taking into account voltage characteristics
Taking into account the voltage characteristics of the load at node i, the following relationship is obtained:
in the formula: i is 1,2, n, PLi and QLi are the active and reactive magnitudes of the load on the ith node, and a, b, c, d, e and f are constant coefficients;
3) dc link power equation
Taking a converter station at the rectification side of a direct current line (LCC-HVDC) as an example, the relationship between the direct current voltage and the direct current of the converter station at the rectification side of the direct current line (LCC-HVDC) in the equivalent model of the converter station in the alternating current-direct current hybrid system is as follows:
in the formula: udr is the DC voltage of the rectifier side converter station; id is direct current; xr is the equivalent commutation reactance of the rectification side; ktr is the transformation ratio of the converter transformer at the rectifying side; ulr is the AC bus voltage of the rectifier side converter station; alpha is a commutation side trigger delay angle;
when the active loss of the commutation process is ignored, the power characteristic equation between the rectifier station and the alternating current system is expressed as follows:
in the formula, Pd and Qd are respectively the active power and the reactive power transmitted to the rectifier station by the alternating current system; pdr is the transmission active power of the rectifier side converter station; cr is equivalent capacitance of a parallel capacitor on an alternating current bus of the rectifier side converter station, and Qcr is reactive output of the parallel capacitor; qdr is the total reactive power consumption of the converter station at the rectifying side; omega is the angular speed of the alternating current system; phi r is the equivalent power factor angle of the rectification side of the direct current system;
4) network equation
Based on the equivalent model of the AC-DC hybrid system and according to the power balance relationship, the active power and the reactive power injected into the network by the node i are respectively as follows:
in the formula: qei is the reactive output of the ith generator; bij is an imaginary part of an admittance array Y of the system network node;
further obtaining according to the power balance relation:
P i +P Li +ξP di ＝0 (11)
Q i +Q Li +ξQ di ＝0 (12)
in the formula: pdi and Qdi are respectively the equivalent active and reactive power of the converter station on the corresponding node, and if the node i has direct current line access, zeta is 1; if the node i has no direct line access, zeta is 0;
and 2, step: theoretical derivation and analysis of the system transient energy function:
the alternating current-direct current hybrid system containing the direct current circuit (LCC-HVDC) can describe the whole dynamic process of the system including a phase-change failure scene of the inversion side of the direct current circuit and can reduce the construction difficulty of an energy function by equivalently constructing the converter stations at two ends of the direct current circuit as the dynamic load of corresponding buses, and the transient energy function of the ith converter station is expressed as follows through the first integral construction:
in the formula: xs is a stable balance point after the fault; x is a current operating point, and in energy function analysis, all transient energy of the direct current system is used as potential energy to be processed;
for the AC-DC hybrid system, the transient energy of the system after the fault is divided into transient kinetic energy and transient potential energy, wherein the transient potential energy consists of AC system potential energy and DC system potential energy, and the value is (theta) s ,ω s ,U s ,Φ s ,t s ) And constructing an energy function for a stable balance point of the system equation after the fault by integrating the system equation for the first time to obtain:
the physical interpretation in the formula is: v pk Transient kinetic energy of the system; v pe Is the transient potential energy of the system, and, V ac Is the transient potential, V, of an AC system d Is the transient potential energy of the dc system;
the transient energy function V is derived with respect to time t, and the result is shown in equations (18), (19), (20):
from the formulae (18), (19), (20):
according to the formula (21), based on a network structure maintenance model, along a trajectory after a fault, a derivative of a constructed transient energy function V with respect to time t is less than or equal to zero, which indicates that the transient energy of the system after the fault of the AC-DC hybrid system is gradually attenuated, and whether a lower bound exists depends on the stable state of the system after the fault;
based on equations (11), (12) and the implicit integral theorem, U, Φ of the system network node is expressed as a function of θ, that is, there are:
the transient potential Vpe of the AC-DC hybrid system is rewritten into
Similarly, equation (14) is rewritten as:
wherein: the transient kinetic energy Vpk and the transient potential energy Vpe after the fault are mutually converted to define dV pc The frequency of 0 is m, which represents the frequency of complete mutual conversion of the transient kinetic energy Vpk and the transient potential energy Vpe of the system after the fault;
performing transient stability analysis on the AC-DC hybrid system by using a Potential Energy Boundary Surface (PEBS) method based on an energy function, and judging whether a current system operating point is separated from the Potential Energy Boundary Surface (PEBS) by using a formula (25) which is popularized from a classical power system model to a network structure maintenance model;
if the μ ray is less than 0 after the fault, representing that the current system operation trajectory is in the PEBS; if the mu ray is greater than 0, the current system operation trajectory is outside the PEBS;
and step 3: transient stability analysis based on energy function:
1) proposing criterion of transient stability
An alternating current fault occurs near the direct current inversion station, so that the inversion side has phase commutation failure; when the AC fault disappears, the DC returns to the normal operation state, the relative rotor angle of the generator gradually converges along with the damping of the system, which shows that the system is in the stable state after the fault and the system mu after the fault ray If the voltage is constant negative, an alternating current fault occurs near the inverter station, so that the phase change failure occurs on the direct current inverter side;
when the AC fault disappears, the generator diverges relative to the rotor angle, namely the system is in an unstable state after the fault, the DC is always in the dynamic regulation process, and the mu of the system after the fault is detected ray From minus at t ═ 0.49sThe value becomes a positive value;
on the basis, a transient stability criterion based on an energy function is provided:
criterion I: if after failure mu ray Changing from negative to positive indicates that the system is in an unstable state;
criterion II: if after failure mu ray The constant is negative until m is 3, which indicates that the system is in a stable state;
2) transient stability margin evaluation
And (3) approximately calculating an energy function curve by adopting a trapezoidal integral path, and quickly obtaining the Critical Clearing Time (CCT) of the AC-DC hybrid system by utilizing a dichotomy (BM), wherein the Critical Clearing Time (CCT) is used as a transient stability margin index.
The invention relates to an alternating Current-Direct Current hybrid system transient stability analysis method considering commutation failure, which aims at an alternating Current-Direct Current hybrid system containing a power grid commutation type High-Voltage Direct Current (LCC-HVDC), constructs a transient energy function containing a Direct Current Line, and carries out transient stability analysis on the alternating Current-Direct Current hybrid system under the scene of commutation failure on a Direct Current inversion side caused by alternating Current fault. Firstly, establishing a network structure maintenance model of an alternating current-direct current hybrid system by equivalently converting a direct current converter station into a dynamic load on a corresponding converter bus, and constructing an energy function of the alternating current-direct current hybrid system through first integration; then, a trapezoidal integral path is adopted to approximately calculate a transient energy function of the system after the fault, a transient stability criterion based on the energy function is provided, and simultaneously, a binary clear Time (CCT) of the system is quickly calculated by using a Binary Method (BM); and finally, an improved IEEE-39 node alternating current-direct current hybrid system is built, and the correctness of the theoretical analysis method is verified through simulation.
The specific embodiment is as follows:
step 1: construction of network structure maintenance model of alternating current-direct current hybrid system
For n nodes, an alternating current-direct current hybrid system with l direct current lines (LCC-HVDC) is combined, wherein i is 1,2, and m is connected with a generator. The synchronous generator is represented by constant E' q, the voltage characteristic of the load is considered, the resistance of the high-voltage line is ignored, two ends of the direct-current line are equivalent to the injection power of the corresponding bus, and an equivalent model based on a system network structure holding model is obtained, as shown in fig. 1.
In the Center of Inertia (COI) reference coordinate, the system equation is:
1) characteristic equation of synchronous generator
In the formula: 1,2, ·, m; theta i and omega i are respectively the power angle and the angular speed of the ith synchronous generator relative to an inertia Center (COI); ui and phi i are respectively the amplitude and phase angle of the ith node; pmi, Pei and Di are respectively the mechanical input power, active power output and damping of the ith generator; mi and PCOI are the inertia time constant and the acceleration power of the inertia Center (COI) of the ith synchronous generator respectively.
2) Load equation taking into account voltage characteristics
Taking into account the voltage characteristics of the load at node i, the following relationship can be obtained:
in the formula: 1,2, n. PLi and QLi are the real and reactive magnitudes of the load on the ith node, respectively. a. b, c, d, e and f are constant coefficients respectively.
3) Dc line power equation
Taking the converter station at the rectification side of the LCC-HVDC converter as an example, the equivalent model of the converter station in the ac-dc hybrid system is shown in fig. 2.
The relation between the direct-current voltage and the direct-current of the LCC-HVDC rectification side converter station obtained from the figure 2 is as follows:
in the formula: udr is the DC voltage of the rectifier side converter station; id is direct current; xr is the equivalent commutation reactance of the rectification side; ktr is the transformation ratio of the converter transformer at the rectifying side; ulr is the AC bus voltage of the rectifier side converter station; α is the commutation side triggered delay angle.
When active loss in the phase commutation process is ignored, the power characteristic equation between the rectifier station and the alternating current system can be expressed as:
in the formula, Pd and Qd are respectively the active power and the reactive power transmitted to the rectifier station by the alternating current system; pdr is the transmission active power of the rectifier side converter station; cr is equivalent capacitance of a parallel capacitor on an alternating current bus of the rectifier side converter station, and Qcr is reactive power output of the parallel capacitor; qdr is the total reactive power consumption of the converter station at the rectifying side; omega is the angular speed of the alternating current system; phi r is the equivalent power factor angle of the rectification side of the direct current system.
4) Network equation
Based on the equivalent model of the AC-DC hybrid system and according to the power balance relationship, the active power and the reactive power injected into the network by the node i are respectively as follows:
in the formula: qei is the reactive output of the ith generator; bij is the imaginary part of the admittance array Y of the network node of the system.
Further derived from the power balance relationship:
P i +P Li +ξP di ＝0 (11)
Q i +Q Li +ξQ di ＝0 (12)
in the formula: and Pdi and Qdi are respectively the equivalent active and reactive sizes of the converter stations on the corresponding nodes. If the node i has a direct current line access, zeta is 1; when the i-node has no direct line access, ζ is 0.
Step 2: theoretical derivation and analysis of system transient energy function
The direct current circuit has the characteristics of complex control, high dynamic regulation speed, phase change failure of a converter station at the inversion side and the like, so that the energy function for constructing and calculating the detailed dynamic process of direct current at two ends is very difficult and tedious, and the direct current circuit alternating current-direct current series-parallel connection system cannot be applied to the scene of phase change failure of the inversion side of the direct current circuit caused by alternating current faults. The transient energy function is constructed by equivalent of the converter stations at the two ends of the direct current line as the dynamic load of the corresponding bus, so that the dynamic overall process of the system including the scene of phase change failure on the inversion side of the direct current line can be described, and the construction difficulty of the energy function can be reduced. Through the first integration construction, the transient energy function of the ith converter station can be expressed as:
in the formula: xs is a stable balance point after the fault; and x is the current operating point. In the energy function analysis, all transient energy of the direct current system is treated as potential energy.
For theIn the alternating current-direct current hybrid system, the transient state energy of the system after the fault can be divided into transient state kinetic energy and transient state potential energy, wherein the transient state potential energy consists of alternating current system potential energy and direct current system potential energy. Let (theta) s ,ω s ,U s ,Φ s ,t s ) For the stable balance point of the system equation after the fault, an energy function is constructed by integrating the system equation for the first time to obtain:
the physical interpretation in the formula is: v pk Is the transient kinetic energy of the system; v pe Is the transient potential of the system. And, V ac Is the transient potential energy of an AC system, V d Is the transient potential energy of the dc system.
The transient energy function V is derived with respect to time t, and the result is shown in equations (18), (19), (20):
the following equations (18), (19) and (20) can be obtained:
from equation (21), based on the network structure maintenance model, along the trajectory after the fault, the derivative of the constructed transient energy function V with respect to time t is less than or equal to zero, which indicates that the transient energy of the system after the fault of the ac/dc hybrid system gradually decays, and whether a lower bound exists will depend on the steady state of the system after the fault.
Based on equations (11), (12) and implicit integration theorem, U, Φ of the system network node can be expressed as a function of θ, that is, there are:
the transient potential Vpe of the AC-DC hybrid system can be rewritten as
Similarly, equation (14) can be rewritten as:
wherein: the transient kinetic energy Vpk and the transient potential energy Vpe after the fault are mutually converted to define dV pe The number of times when/dt is 0 is m, which represents the number of times that the system transient kinetic energy Vpk and the transient potential energy Vpe complete one-time mutual conversion after the fault.
Transient stability analysis of the AC-DC hybrid system is performed by adopting a Potential Energy Boundary Surface (PEBS) method based on an Energy function, and whether the current system operating point is separated from a Potential Energy Boundary Surface (PEBS) is judged by using a formula (25) which is popularized from a classical power system model to a network structure retention model.
If the μ ray is less than 0 after the fault, representing that the current system operation trajectory is in the PEBS; if μ ray >0, it represents that the current system operation trajectory is outside the PEBS.
And 3, step 3: transient stability analysis based on energy function
1) Proposing criterion of transient stability
Taking the CEPRI-7 system as an example, the network structure is shown in FIG. 3. Critical cut-off angle gamma of DC inversion side min The generator in the system has uniform damping at 7 deg., i.e., Di/Mi. Three-phase short circuit fault occurs at the Bus-6 position, which causes commutation failure at the direct current inversion side, so that the system is in critical stable and unstable states after the fault.
The calculation results are shown in fig. 4 and 5, respectively. In fig. 4(a) and 5(a), the blue solid line and the red solid line represent the real-time off angle and the critical off angle of the dc link, respectively. The solid blue line in fig. 4(b) and 5(b) represents the dc power. The solid blue line in fig. 4(c) and 5(c) indicates the relative rotor angle of the generator. The solid blue line in FIGS. 4(d) and 5(d) depicts μ ray A curve. As can be seen from fig. 4(a) and 4(b), an ac fault occurs near the dc inverter station, which results in a phase change failure on the inverter side; and when the alternating current fault disappears, the direct current restores to a normal operation state. As can be seen from fig. 4(c), the relative rotor angle of the generator gradually converges with the damping of the system, indicating that the system is in a steady state after a fault; as shown in FIG. 4(d), post-fault system μ ray And is always negative. As can be seen from fig. 5(a) and 5(b), an ac fault occurs near the inverter station, resulting in a phase change failure on the dc inverter side. When the ac fault disappears, the dc is always in the dynamic regulation process because the generator in fig. 5(c) diverges with respect to the rotor angle, i.e., the system is in an unstable state after the fault. As shown in FIG. 5(d), μ of post-fault system ray Changes from negative to positive at t-0.49 s.
On the basis, a transient stability criterion based on an energy function is provided:
criterion I: if after failure mu ray Changing from negative to positive indicates that the system is in an unstable state;
criterion II: if after failure mu ray It is always negative until m is 3, indicating that the system is in steady state.
2) Transient stability margin assessment
Fig. 6 shows a flow chart of transient stability margin evaluation of the ac/dc hybrid system, where ∈ h, and h is a simulation step size. "[ ]" denotes a rounding function. An energy function curve is approximately calculated by adopting a trapezoidal integral path, and the Critical Clearing Time (CCT) of the AC-DC hybrid system is quickly obtained by utilizing a dichotomy (BM), wherein the CCT can be used as a transient stability margin index.
The technical effects are as follows:
1) simulation verification
An improved IEEE-39 node alternating current and direct current hybrid system is built, and the correctness and the effectiveness of the theoretical method provided by the text are verified. The network topology is as shown in fig. 7, and on the premise of not changing the power flow of the system, the alternating current connecting line between the Bus-16 and the Bus-15 is changed into LCC-HVDC, wherein the Bus-16 is a rectifying station Bus, and the Bus-15 is an inverting station Bus. And, critical off angle gamma of DC inversion side min And 7 degrees, the generator in the alternating current and direct current system has uniform damping, namely, the lambda is Di/Mi.
In an alternating current system near a direct current inversion station, a three-phase short-circuit fault which causes commutation failure on a direct current inversion side is set. The simulation step h is 0.01s, and the simulation time T is 5 s. Selecting x c Is potential energy V pe The start of integration of (a). Under the following four scenes, transient stability evaluation is performed on the AC-DC hybrid system after the fault by adopting a transient stability criterion based on an energy function.
Scene I: a three-phase short circuit fault occurs at the Bus-14 of the ac system. The fault starts at t-0 and has a fault duration of 0.20 s.
The simulation results are shown in fig. 8. The blue solid line and the red solid line in fig. 8(a) respectively depict the real-time off-angle and critical off-angle variation curves of the dc line. The blue solid lines in fig. 8(b) respectively show the relative angle change curves of the generator rotor. In FIG. 8(c)The blue solid line, the red solid line and the black solid line respectively represent the potential energy V of the system after the fault pe Kinetic energy V pk And total energy change curve. The solid blue line in FIG. 8(d) depicts μ after failure ray A curve of variation.
As can be seen from fig. 8(a), the ac system near the inverter station fails, and the dc inverter side fails to perform commutation. And after the AC fault disappears, the DC line is restored to a normal operation state under the regulation of the DC control system. As shown in fig. 8(b), under the effect of system damping, the relative rotor angle of the generator gradually converges to the stable equilibrium point before failure, which indicates that the system is in a stable state after failure. As can be seen from fig. 8(c), the derivative of the energy function V of the post-fault system is always non-positive, and when the post-fault system is in a steady state, the energy function V has a lower bound, which proves the correctness of the energy function proposed herein. As shown in FIG. 8(d), μ of post-fault system ray And is constantly negative during the period when m is 3. According to the transient stability criterion, the system after the fault is in a stable state, and the analysis result is matched with the simulation result.
And scene II: a three-phase short circuit fault occurs at the Bus-14 of the ac system. The fault starts at t-0 and has a fault duration of 0.29 s.
As can be seen from fig. 9(a), an ac system near the inverter station fails, and a commutation failure occurs on the dc inverter side. After the ac fault disappears, the generator shown in fig. 9(b) gradually diverges from the rotor angle, i.e., it is shown that the system is in an unstable state after the fault, and the dc line is always in the dynamic adjustment process. As can be seen from fig. 9(c), the derivative of the post-fault system energy function V is always non-positive, and when the post-fault system is in an unstable state, the energy function V is unbounded, proving the correctness of the energy function proposed herein. As shown in FIG. 9(d), μ of post-fault system ray And the t is changed from negative to positive in 1.23 s. According to the transient stability criterion, the system after the fault is in an unstable state, and the analysis result is matched with the simulation result.
Scene III: a three-phase short circuit fault occurs at the Bus-14 of the ac system. The fault starts at t-0 and has a fault duration of 0.20 s. Furthermore, when t is 0.20s, the ac line between Bus-4 and Bus-14 is cut off.
As can be seen from fig. 10(a), an ac system near the inverter station fails, and a commutation failure occurs on the dc inverter side. And after the AC fault disappears, the DC line is restored to a normal running state under the regulation of the DC control system. As shown in fig. 10(b), under the effect of system damping, the relative rotor angle of the generator gradually converges to a new stable equilibrium point, which indicates that the system is in a stable state after a fault. As can be seen from fig. 10(c), the derivative of the energy function V of the post-fault system is always non-positive, and when the post-fault system is in a steady state, the energy function V has a lower bound, which proves the correctness of the energy function proposed herein. As shown in FIG. 10(d), post-fault system μ ray And is constantly negative during the period when m is 3. According to the transient stability criterion, the system after the fault is in a stable state, and the analysis result is matched with the simulation result. Compared to scenario I, the proposed method will be effective regardless of whether the system stable equilibrium point changes after a fault.
Scenario iv: and a three-phase short-circuit fault occurs at the Bus-14 of the alternating current system. The fault starts at t-0 and has a fault duration of 0.20 s. Furthermore, when t is 0.28s, the ac line between Bus-4 and Bus-14 is cut off.
As can be seen from fig. 11(a), an ac system near the inverter station has a fault, and a commutation fault occurs on the dc inverter side. After the ac fault disappears, the generator shown in fig. 11(b) gradually diverges from the rotor angle, i.e., it is described that the system is in an unstable state after the fault, and the dc line is always in the dynamic adjustment process. As can be seen from fig. 11(c), the derivative of the energy function V of the post-fault system is always non-positive, and when the post-fault system is in an unstable state, the energy function V is unbounded, which proves the correctness of the energy function proposed herein. As shown in FIG. 11(d), μ of post-fault system ray And the t is changed from negative to positive in 1.17 s. According to the transient stability criterion, the system after the fault is in an unstable state, and the analysis result is matched with the simulation result. Compared with the scenario II, the proposed method is effective no matter whether the stable balance point of the system changes after the fault.
2) Comparative analysis
Aiming at different positions of an alternating current system near an inverter station, a three-phase short-circuit fault which can cause a direct current commutation fault is set so as to simulate an alternating current fault accompanied with a commutation fault scene in an improved IEEE-39 node alternating current and direct current hybrid system. The CCT of the ac/dc hybrid system is calculated by using an Energy Function Criterion (EFC) and a Time Domain Simulation (TDS), respectively, and the result is shown in table 1.
TABLE 1 comparison of CCTs calculated by different methods under different scenarios
"/" indicates that no wires are cut.
According to table 1, it can be seen that, when an ac fault and a commutation fault occur in the ac/dc hybrid system, the transient stability evaluation result of the theoretical method provided herein is substantially consistent with the time domain simulation result. Under 20 scenes, CCT calculation results obtained by adopting EFC are about 0-0.01 s more than TDS conservation, and the effectiveness and the practicability of the method are verified.
Then, the time spent on calculating the CCT of the AC-DC hybrid system by respectively adopting EFC and TDS in different scenes is researched. The computation time of the CCT varies from hardware environment to hardware environment, and the computation time is mainly the time spent in simulation. Thus, in the comparison of Table 2, the total simulation duration is taken to represent the time taken to calculate the CCT, rather than the actual calculation time. When the alternating current-direct current hybrid system CCT is rapidly obtained by using the BM, the upper limit and the lower limit of the BM are respectively set to be 0.1s and 0.9 s. The simulation time was 5s, and the simulation results are shown in table 2.
TABLE 2 time comparison of CCT calculations by different methods under different scenarios
"/" indicates that no wires are cut.
As shown in table 2, in 20 scenarios, the time spent on calculating the CCT of the ac/dc hybrid system by using EFC is shorter than TDS. The CCT calculation speed by adopting EFC is 2-3 times faster than that of TDS, and the efficiency of dynamic security evaluation of the AC-DC hybrid system is greatly improved. In addition, when the CCT is calculated by TDS, it is impossible to quantitatively determine whether the system is stable after a fault by observing the relative rotor angle of the generator, and the EFC can solve this problem.
The above description is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are also within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (1)
1. The method for analyzing the transient stability of the alternating current-direct current hybrid system in consideration of the commutation failure is characterized in that a transient energy function containing a direct current line is constructed for the alternating current-direct current hybrid system containing a power grid commutation type high-voltage direct current transmission line, and the transient stability analysis is performed on the alternating current-direct current hybrid system under the situation that the commutation failure occurs on a direct current inversion side caused by an alternating current fault, and comprises the following steps:
firstly, establishing a network structure maintenance model of an alternating current-direct current hybrid system by equivalently using a direct current convertor station as a dynamic load on a corresponding convertor bus, and constructing an energy function of the alternating current-direct current hybrid system through first integration;
secondly, a trapezoidal integral path is adopted to approximately calculate a transient energy function of the system after the fault, a transient stability criterion based on the energy function is provided, and meanwhile, the dichotomy is utilized to quickly calculate the limit cut-off time of the system;
finally, an improved IEEE-39 node alternating current-direct current hybrid system is built, and the correctness of the theoretical analysis method is verified through simulation;
the method specifically comprises the following steps:
step 1: constructing a network structure maintenance model of the AC-DC hybrid system:
for an alternating current-direct current (LCC-HVDC) system with n nodes and l direct current lines, wherein i is 1,2, the.cndot.m nodes are connected with a generator, the synchronous generator adopts E' q constant representation, the voltage characteristic of a load is considered, the resistance of the high voltage line is ignored, the two ends of the direct current lines are equivalent to the injection power of the corresponding bus, and an equivalent model based on a system network structure maintenance model is obtained;
at the center of inertia (COI) reference coordinates, the system equation is:
1) characteristic equation of synchronous generator
In the formula: 1,2, ·, m; theta i and omega i are respectively the power angle and the angular speed of the ith synchronous generator relative to an inertia Center (COI); ui and phi i are respectively the amplitude and phase angle of the ith node; pmi, Pei and Di are respectively the mechanical input power, active power output and damping of the ith generator; mi and PCOI are respectively an inertia time constant and an acceleration power of an inertia Center (COI) of the ith synchronous generator;
2) load equation taking into account voltage characteristics
Taking into account the voltage characteristics of the load at node i, the following relationship is obtained:
in the formula: i is 1,2, n, PLi and QLi are the active and reactive sizes of the load on the ith node, and a, b, c, d, e and f are constant coefficients;
3) dc line power equation
Taking a converter station at the rectification side of a direct current line (LCC-HVDC) as an example, the relation between the direct current voltage and the direct current of the converter station at the rectification side of the direct current line (LCC-HVDC) in the equivalent model of the converter station in the alternating current-direct current hybrid system is as follows:
in the formula: udr is the DC voltage of the rectifier side converter station; id is direct current; xr is the equivalent commutation reactance of the rectification side; ktr is the transformation ratio of the converter transformer at the rectifying side; ulr is the AC bus voltage of the rectifier side converter station; alpha is a commutation side trigger delay angle;
when active loss in the phase commutation process is ignored, the power characteristic equation between the rectifier station and the alternating current system is expressed as:
in the formula, Pd and Qd are respectively the active power and the reactive power transmitted to the rectifier station by the alternating current system; pdr is the transmission active power of the rectifier side converter station; cr is equivalent capacitance of a parallel capacitor on an alternating current bus of the rectifier side converter station, and Qcr is reactive output of the parallel capacitor; qdr is the total reactive power consumption of the converter station at the rectifying side; omega is the angular speed of the alternating current system; phi r is the equivalent power factor angle of the rectification side of the direct current system;
4) network equation
Based on the equivalent model of the AC-DC hybrid system and according to the power balance relationship, the active power and the reactive power injected into the network by the node i are respectively as follows:
in the formula: qei is the reactive output of the ith generator; bij is the imaginary part of the system network node admittance array Y;
further obtaining according to the power balance relation:
P i +P Li +ξP di ＝0 (11)
Q i +Q Li +ξQ di ＝0 (12)
in the formula: pdi and Qdi are respectively the equivalent active and reactive power of the converter station on the corresponding node, and if the node i has direct current line access, zeta is 1; if the node i has no direct line access, zeta is 0;
step 2: theoretical derivation and analysis of the system transient energy function:
the alternating current-direct current hybrid system containing the direct current circuit (LCC-HVDC) can describe the whole dynamic process of the system including a phase-change failure scene of the inversion side of the direct current circuit and can reduce the construction difficulty of an energy function by equivalently constructing the converter stations at two ends of the direct current circuit as the dynamic load of corresponding buses, and the transient energy function of the ith converter station is expressed as follows through the first integral construction:
in the formula: xs is a stable balance point after failure; x is a current operating point, and all transient energy of the direct current system is treated as potential energy in energy function analysis;
for the AC-DC hybrid system, the transient energy of the system after the fault is divided into transient kinetic energy and transient potential energy, wherein the transient potential energy consists of AC system potential energy and DC system potential energy, and the value is (theta) s ,ω s ,U s ,Φ s ,t s ) And constructing an energy function for a stable balance point of the system equation after the fault by integrating the system equation for the first time to obtain:
the physical interpretation in the formula is: v pk Is the transient kinetic energy of the system; v pe Is the transient potential energy of the system, and, V ac Is the transient potential energy of an AC system, V d Is the transient potential energy of the dc system;
the transient energy function V is derived with respect to time t, and the result is shown in equations (18), (19), (20):
from the formulae (18), (19), (20):
according to the formula (21), based on a network structure maintenance model, along the trajectory after the fault, the derivative of the constructed transient energy function V with respect to the time t is less than or equal to zero, which indicates that the transient energy of the system after the fault of the AC-DC hybrid system is gradually attenuated, and whether a lower bound exists depends on the stable state of the system after the fault;
based on equations (11), (12) and the implicit integral theorem, U, Φ of the system network node is expressed as a function of θ, that is, there are:
the transient potential energy Vpe of the AC-DC hybrid system is rewritten to
Similarly, equation (14) is rewritten as:
wherein: the transient kinetic energy Vpk and the transient potential energy Vpe after the fault are mutually converted to define dV pe The frequency of 0 is m, which represents the frequency of complete mutual conversion of the transient kinetic energy Vpk and the transient potential energy Vpe of the system after the fault;
performing transient stability analysis on the AC-DC hybrid system by using a Potential Energy Boundary Surface (PEBS) method based on an energy function, and judging whether a current system operating point is separated from a Potential Energy Boundary Surface (PEBS) or not by using a formula (25) popularized from a classical power system model to a network structure retention model;
if the μ ray is less than 0 after the fault, representing that the current system operation trajectory is in the PEBS; if the mu ray is greater than 0, the current system operation trajectory is outside the PEBS;
and step 3: transient stability analysis based on energy function:
1) proposing criterion of transient stability
An alternating current fault occurs near the direct current inversion station, so that the inversion side has phase commutation failure; when the AC fault disappears, the DC returns to the normal operation state, the relative rotor angle of the generator gradually converges along with the damping of the system, which shows that the system is in the stable state after the fault and the system mu after the fault ray If the voltage is constant negative, an alternating current fault occurs near the inverter station, so that the phase change failure occurs on the direct current inverter side;
when the AC fault disappears, the generator diverges relative to the rotor angle, namely the system is in an unstable state after the fault, the DC is always in the dynamic regulation process, and the mu of the system after the fault is detected ray Changes from negative to positive at t-0.49 s;
on the basis, a transient stability criterion based on an energy function is provided:
criterion I: if after failure mu ray Changing from negative to positive indicates that the system is in an unstable state;
criterion II: if after failure mu ray The constant is negative until m is 3, which indicates that the system is in a stable state;
2) transient stability margin evaluation
And (3) approximately calculating an energy function curve by adopting a trapezoidal integral path, and quickly obtaining the Critical Clearing Time (CCT) of the AC-DC hybrid system by utilizing a dichotomy (BM), wherein the Critical Clearing Time (CCT) is used as a transient stability margin index.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011083828.XA CN112165114B (en) | 2020-10-12 | 2020-10-12 | Alternating current-direct current hybrid system transient stability analysis method considering commutation failure |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011083828.XA CN112165114B (en) | 2020-10-12 | 2020-10-12 | Alternating current-direct current hybrid system transient stability analysis method considering commutation failure |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN112165114A CN112165114A (en) | 2021-01-01 |
| CN112165114B true CN112165114B (en) | 2022-09-23 |
Family
ID=73866391
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202011083828.XA Active CN112165114B (en) | 2020-10-12 | 2020-10-12 | Alternating current-direct current hybrid system transient stability analysis method considering commutation failure |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN112165114B (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112865167B (en) * | 2021-04-12 | 2022-03-15 | 华北电力大学 | Method and system for determining transient stability margin of alternating current-direct current hybrid system |
| CN112994072B (en) * | 2021-04-27 | 2022-08-19 | 华北电力大学 | Two-port equivalent modeling method suitable for back-to-back VSC fault transient calculation |
| CN115065103B (en) * | 2022-08-12 | 2022-11-11 | 中国电力科学研究院有限公司 | New energy access capacity determination method and system based on commutation failure frequency constraint |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2005057872A (en) * | 2003-08-04 | 2005-03-03 | Meidensha Corp | Method for analyzing transient stability of induction generator |
| CN104242305A (en) * | 2014-09-11 | 2014-12-24 | 清华大学 | New energy-containing power system transient stability energy function analysis method |
| CN106709147A (en) * | 2016-11-25 | 2017-05-24 | 广西电网有限责任公司电力科学研究院 | BPA-based method for automatically solving limit clearing time of short circuit faults in batches |
| CN110739716A (en) * | 2019-11-27 | 2020-01-31 | 广东电网有限责任公司 | calculation method for transient stability limit cutting time of power grid |
| CN111030112A (en) * | 2020-01-02 | 2020-04-17 | 北京交通大学 | Method for judging transient stability of alternating current-direct current hybrid power system containing flexible direct current |
-
2020
- 2020-10-12 CN CN202011083828.XA patent/CN112165114B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2005057872A (en) * | 2003-08-04 | 2005-03-03 | Meidensha Corp | Method for analyzing transient stability of induction generator |
| CN104242305A (en) * | 2014-09-11 | 2014-12-24 | 清华大学 | New energy-containing power system transient stability energy function analysis method |
| CN106709147A (en) * | 2016-11-25 | 2017-05-24 | 广西电网有限责任公司电力科学研究院 | BPA-based method for automatically solving limit clearing time of short circuit faults in batches |
| CN110739716A (en) * | 2019-11-27 | 2020-01-31 | 广东电网有限责任公司 | calculation method for transient stability limit cutting time of power grid |
| CN111030112A (en) * | 2020-01-02 | 2020-04-17 | 北京交通大学 | Method for judging transient stability of alternating current-direct current hybrid power system containing flexible direct current |
Non-Patent Citations (1)
| Title |
|---|
| 交直流混联系统稳定性分析研究综述;刘垚 等;《电工电能新技术》;20200930;第36-47页 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN112165114A (en) | 2021-01-01 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN112165114B (en) | Alternating current-direct current hybrid system transient stability analysis method considering commutation failure | |
| CN104466984B (en) | Dynamic reactive standby optimization method for increasing safety level of direct current commutation | |
| CN110718918B (en) | Load flow calculation method based on HVAC and LCC-VSC HVDC hybrid system | |
| CN112865167B (en) | Method and system for determining transient stability margin of alternating current-direct current hybrid system | |
| CN105896586A (en) | Method and system for fault positioning and recovery of voltage source converter | |
| CN103825478A (en) | Control method of modular multilevel converter based on power frequency fixed switching frequency | |
| CN109659968B (en) | Electromechanical transient modeling method for distributed access type LCC-MMC (lower control limit-multilevel converter) mixed direct-current system | |
| CN111463811B (en) | MMHC energy storage system control method based on battery energy balance | |
| Zhou et al. | Common‐mode voltage injection‐based nearest level modulation with loss reduction for modular multilevel converters | |
| CN108988320B (en) | Method for analyzing influence of response characteristic of dynamic element of power system on transient voltage stability | |
| CN104734537A (en) | Control method for wind power current converter based on positive-and-negative sequence current inner-loop control | |
| CN105897025A (en) | Modular multilevel converter sub-module voltage equalization method | |
| CN108418442B (en) | Sliding mode control method for integral terminal of high-voltage direct-current transmission system of two-end voltage source type converter | |
| Gao et al. | Fast Decoupled Power Flow Calculation with Complementary Constraints of Reactive Power Generation and Node Voltage | |
| CN115714404A (en) | Commutation soft switching system for governing current unbalance of power distribution network and evaluation method | |
| Islam et al. | PHEV's park as a virtual active filter for HVDC networks | |
| CN114421511A (en) | Control method and device of hybrid direct-current transmission equipment and hybrid direct-current transmission system | |
| Torres-Olguin et al. | Grid Integration of offshore wind farms using a Hybrid HVDC composed by an MMC with an LCC-based transmission system | |
| Hasabelrasul et al. | Cascaded H-bridge multilevel inverter balancing for energy-power based on VSG | |
| Jiang et al. | Small-signal modeling and interaction analysis of LCC-HVDC systems based on harmonic state space theory | |
| CN104167757B (en) | A kind of electric power system based on seawave power generation | |
| Sun et al. | Steady-State Voltage Stability Analysis of AC-DC Hybrid Power System with VSC-HVDC | |
| CN113139152B (en) | Method and system for evaluating adaptability of instantaneous load of direct-current distribution network of offshore oil production platform | |
| CN118054427B (en) | Operation control method of unified power quality regulator | |
| CN113705144B (en) | Half-bridge type MMC electromagnetic transient simulation method considering blocking |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |