CN115513939A - Method and device for switching operation modes of converter - Google Patents
Method and device for switching operation modes of converter Download PDFInfo
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- H—ELECTRICITY
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- 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
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
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- 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
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Abstract
The invention discloses a switching method of converter operation modes, wherein grid-forming converters are uniformly distributed on all new energy power source nodes according to the topology of an actual power grid system, a corresponding simulation system is built, different faults are set at the positions of all possible fault nodes of the simulation system to drop the voltage of the power grid, each fault is simulated, the corresponding relation between the transient power angle and the time of each grid-forming converter under each fault is obtained, the comprehensive participation factor of each grid-forming converter is determined based on the corresponding relation under each fault, the node position of a target grid-forming converter with the comprehensive participation factor smaller than a preset threshold value is switched to a grid-following converter by the target grid-forming converter. The method is based on the solving idea of actual simulation and actual measurement of the disturbed track of the power grid system, considers the disturbed dynamic response characteristics of the network-forming type converter and the network-following type converter under different faults, and overcomes the defect of inaccuracy caused by guiding the operation mode switching of the converter only by means of a short-circuit ratio index in the prior art.
Description
Technical Field
The invention relates to the technical field of converters, in particular to a method and a device for switching operation modes of a converter.
Background
According to different control strategies of the voltage source type converter, the operation modes of the converter can be divided into a following network type converter and a network type converter. The network-following type converter realizes synchronization with an alternating current power network by using a phase-locked loop, injects set current to complete the power generation target along with the voltage of an accessed alternating current bus, and can ensure the stability of the operation of a power network system under the strong power network strength. However, the network-following type converter does not have the power and power angle equation constraints of the synchronous motor, and also does not have the instantaneous power sharing capability, so that more negative damping can be introduced into the network-following type converter under the weak network strength, which is not beneficial to the improvement of the operation stability of the power network system. The network-based converter generally adopts power control to realize a synchronization function and simultaneously performs power regulation. The dc side of the grid-type converter is equipped with energy storage units to provide additional power support in the dynamic process. The network-constructing type converter overcomes the defect of a phase-locked loop by integrating the synchronous function into the power controller, so that the network-constructing type converter can maintain the operation stability of a power grid system under the weak power grid strength, and the problem of the network-following type converter under the weak power grid strength is solved. However, the grid-type converter is not beneficial to improving the operation stability of the grid system under the condition of strong grid strength.
Aiming at the characteristics of a network following type converter and a network construction type converter in the aspect of power grid system stability under different power grid strengths, the network following type converter and the network construction type converter are switched according to an equivalent short circuit ratio of a power grid system when a voltage source type converter is switched so as to maintain the operation stability of the power grid system.
However, the equivalent short-circuit ratio only considers the power frequency static characteristics of the rated working point, and cannot reflect the influence of the dynamic characteristics, the output characteristics and the like of each control loop in the converter, so that the switching of the operation mode of the existing converter cannot reflect the actual power grid topology condition, and the operation stability of a power grid system cannot be ensured.
Disclosure of Invention
In view of this, the invention discloses a method and a device for switching a converter operation mode, so as to realize a solving idea based on actual simulation and actual measurement of disturbed track of a power grid system, consider disturbed dynamic response characteristics of a grid-forming type converter and a grid-following type converter under different faults, and overcome the defect of inaccuracy caused by guiding the converter operation mode switching only by means of a short-circuit ratio index representing a power frequency static characteristic of a rated working point in the prior art.
A method for switching the operation modes of a converter comprises the following steps:
according to the actual power grid system topology, network-forming type converters are uniformly distributed on all new energy power source nodes, and a simulation system formed by the distributed network-forming type converters is built;
setting different faults at each possible fault node position of the simulation system to drop the voltage of the power grid;
simulating each fault to obtain the corresponding relation between the transient power angle and the time of each network-type converter under each fault;
determining a comprehensive participation factor of each networking type converter based on the corresponding relation between the transient state power angle and the time of each networking type converter under different faults, wherein the numerical value of the comprehensive participation factor is used for representing the interference degree of the networking type converters under different faults;
and switching the node position of the target network-forming type converter with the comprehensive participation factor smaller than a preset threshold value into a network-following type converter by the target network-forming type converter.
Optionally, the determining, based on a corresponding relationship between the transient power angle and time of each networking type converter under different faults, a comprehensive participation factor of each networking type converter includes:
determining participation factors of each networking type converter based on the corresponding relation between the transient state power angle and the time of each networking type converter under the condition of single fault, wherein the participation factors are used for representing the interference degree of the networking type converter under the condition of single fault;
and obtaining the comprehensive participation factor of each network-forming type converter based on the corresponding participation factor of each network-forming type converter under different faults and the occurrence probability of different faults.
Optionally, the determining the participation factor of each network type converter based on the corresponding relationship between the transient power angle and the time of each network type converter under the single fault includes:
determining a first rotor angle of the network type converter corresponding to a first moment in a mature period of the transient process and a second rotor angle of the network type converter corresponding to a second moment based on the corresponding relation between the transient power angle and time of each network type converter under a single fault, wherein the first moment and the second moment are any two moments in the mature period of the transient process;
calculating a rotor angle difference of a second rotor angle of the network-forming type converter and a first rotor angle of the network-forming type converter corresponding to each network-forming type converter;
determining the participation factor of the target network-forming type converter with the highest rotor angle difference value as 1;
and determining the participation factors of the network-forming type converters except the target network-forming type converter based on the target rotor angle difference corresponding to the target network-forming type converter.
Optionally, the determining the participation factor of each network type converter except the target network type converter based on the target rotor angle difference corresponding to the target network type converter includes:
and calculating a quotient value of the rotor angle difference of each network-type converter except the target network-type converter and the target rotor angle difference, and determining the quotient value as the participation factor of the corresponding network-type converter.
Optionally, each networking type converter is a virtual synchronous machine, and the networking simulation parameters of the virtual synchronous machines are the same or different.
Optionally, each of the possible fault node positions is arranged on the ac system side.
Optionally, the simulating each fault to obtain a corresponding relationship between a transient power angle and time of each networking type converter under each fault includes:
and simulating the electromagnetic transient condition of each networking type converter aiming at each fault to obtain the corresponding relation between the transient power angle and time of each networking type converter under each fault, wherein the transient power angle is determined based on the active loop output phase angle and the grid phase angle of the networking type converter.
A converter operating mode switching apparatus comprising:
the simulation system building unit is used for uniformly distributing networking type converters on all new energy power supply nodes according to the actual power grid system topology and building a simulation system formed by the distributed networking type converters;
the fault setting unit is used for setting different faults at each possible fault node position of the simulation system so as to drop the voltage of the power grid;
the simulation unit is used for simulating each fault to obtain the corresponding relation between the transient power angle and the time of each networking type converter under each fault;
the determining unit is configured to determine an integrated participation factor of each networking type converter based on a corresponding relation between the transient power angle and time of each networking type converter under different faults, where a numerical value of the integrated participation factor is used to represent interference degrees of the networking type converters under different faults;
and the switching unit is used for switching the node position of the target network-forming type converter with the comprehensive participation factor smaller than a preset threshold value into the network-following type converter by the target network-forming type converter.
Optionally, the determining unit includes:
the participation factor determining subunit is configured to determine a participation factor of each networking type converter based on a corresponding relationship between the transient power angle and time, corresponding to each networking type converter under a single fault, where the participation factor is used to characterize an interference degree of the networking type converter under the single fault;
and the comprehensive participation factor determining subunit is used for obtaining the comprehensive participation factor of each network type converter based on the corresponding participation factor of each network type converter under different faults and the occurrence probability of different faults.
Optionally, the participation factor determining subunit is specifically configured to:
determining a first rotor angle of the network type converter corresponding to a first moment in a mature period of the transient process and a second rotor angle of the network type converter corresponding to a second moment based on the corresponding relation between the transient power angle and time of each network type converter under a single fault, wherein the first moment and the second moment are any two moments in the mature period of the transient process;
calculating a rotor angle difference of a second rotor angle of the network-forming type converter and a first rotor angle of the network-forming type converter corresponding to each network-forming type converter;
determining the participation factor of the target network-forming type converter with the highest rotor angle difference value as 1;
and determining the participation factors of the network-forming type converters except the target network-forming type converter based on the target rotor angle difference corresponding to the target network-forming type converter.
Optionally, the participation factor determining subunit is further specifically configured to:
and calculating a quotient value of the rotor angle difference of each network-type converter except the target network-type converter and the target rotor angle difference, and determining the quotient value as the participation factor of the corresponding network-type converter.
Optionally, the simulation unit is specifically configured to:
and simulating the electromagnetic transient condition of each networking type converter aiming at each fault to obtain the corresponding relation between the transient power angle and time of each networking type converter under each fault, wherein the transient power angle is determined based on the active loop output phase angle and the grid phase angle of the networking type converter.
From the above technical solution, the present invention discloses a method and an apparatus for switching an operation mode of a converter, where the method includes: according to the actual power grid system topology, networking type converters are uniformly distributed on all new energy power source nodes, a simulation system formed by the distributed networking type converters is built, different faults are set at the positions of the possible fault nodes of the simulation system, the voltage of a power grid drops, each fault is simulated, the corresponding relation between the transient power angle and the time of each networking type converter under each fault is obtained, the comprehensive participation factor of each networking type converter is determined based on the corresponding relation between the transient power angle and the time of each networking type converter under different faults, when the comprehensive participation factor is smaller than a preset threshold value, the interference degree of the networking type converter is high, the networking type converter is in weak power grid strength at the moment, in order to guarantee the operation stability of the power grid system, the target networking type converter under the weak power grid strength is switched to a network following type converter, and the switching of the operation modes of the converters is realized. The method is based on the solving idea of actual simulation and actual measurement of the disturbed track of the power grid system, considers the disturbed dynamic response characteristics of the network-forming type converter and the network-following type converter under different faults and is not the static characteristic under one working condition, and overcomes the defect of inaccuracy caused by guiding the operation mode switching of the converter only by means of the short-circuit ratio index representing the power frequency static characteristic of the rated working point in the prior art.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the disclosed drawings without creative efforts.
Fig. 1 is a flowchart of a method for switching an operation mode of a converter according to an embodiment of the present invention;
fig. 2 is a flowchart of a method for determining an integrated participation factor of each network type converter according to an embodiment of the present invention;
fig. 3 is a flowchart of a method for determining a participation factor of each network type converter according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of a switching device for operating modes of a converter according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of a determining unit according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The embodiment of the invention discloses a method and a device for switching the operation modes of a converter, wherein the method comprises the following steps: according to the actual power grid system topology, grid-forming type converters are uniformly distributed on all new energy power source nodes, a simulation system formed by the distributed grid-forming type converters is built, different faults are set at the positions of the possible fault nodes of the simulation system, the voltage of a power grid drops, the faults are simulated, the corresponding relation between the transient power angle and the time of each grid-forming type converter under each fault is obtained, the comprehensive participation factor of each grid-forming type converter is determined based on the corresponding relation between the transient power angle and the time of each grid-forming type converter under different faults, when the comprehensive participation factor is smaller than a preset threshold value, the interference degree of the grid-forming type converter is high, the grid-forming type converter is in weak power grid strength at the moment, and in order to guarantee the operation stability of the power grid system, the target grid-forming type converter under the weak power grid strength is switched to a grid-following type converter, and the switching of the operation modes of the converters is realized. The method is based on the solving idea of actual simulation and actual measurement of the disturbed track of the power grid system, considers the disturbed dynamic response characteristics of the network-forming type converter and the network-following type converter under different faults and is not the static characteristic under one working condition, and overcomes the defect of inaccuracy caused by guiding the operation mode switching of the converter only by means of the short-circuit ratio index representing the power frequency static characteristic of the rated working point in the prior art.
Referring to fig. 1, a flow chart of a method for switching an operating mode of a converter according to an embodiment of the present invention includes:
step S101, according to the actual power grid system topology, networking type converters are uniformly distributed on all new energy power source nodes, and a simulation system formed by the distributed networking type converters is built;
according to the embodiment, firstly, networking type converters are uniformly distributed on all new energy power supply nodes according to the actual power grid system topology, and then a simulation system formed by the networking type converters is built in electromagnetic transient simulation software (such as PSCAD) according to the distributed networking type converters.
In practical application, each network-forming type converter may be a virtual synchronous machine, and the network-forming simulation parameters of each virtual synchronous machine may be the same or different, specifically according to actual needs, and the present invention is not limited herein.
S102, setting different faults at each possible fault node position of the simulation system to drop the voltage of the power grid;
wherein the possible failure node is determined according to the historical failure node.
In the embodiment, different faults are set at each possible fault node position of the simulation system, so that each possible fault node position is disturbed, and the voltage of the power grid drops.
In practical application, the positions of the possible fault nodes are set at the side of the alternating current system, the fault type is determined according to actual needs, for example, a symmetric short-circuit fault, and the fault clearing time τ can be uniformly set to 0.1s, and of course, the fault clearing time τ can also be set to other times as needed.
S103, simulating each fault to obtain the corresponding relation between the transient power angle and the time of each network type converter under each fault;
the corresponding relationship between the transient power angle and the time of the grid-structured converter may be a transient power angle-time (δ -t) curve.
Step S104, determining comprehensive participation factors of each network type converter based on the corresponding relation between the transient power angle and the time of each network type converter under different faults;
the numerical value of the comprehensive participation factor is used for representing the interference degree of the network-structured converter under different faults. The higher the value of the comprehensive participation factor is, the weaker the interference degree of the network-structured type converter is, and the strong power network strength of the network-structured type converter is indicated; on the contrary, the lower the value of the comprehensive participation factor is, the stronger the interference degree of the network type converter is, and the network type converter is in weak power grid strength at the moment.
And S105, switching the node position of the target network-forming type converter with the comprehensive participation factor smaller than a preset threshold value into a network-following type converter by the target network-forming type converter.
When the comprehensive participation factor is smaller than a preset threshold value, the interference degree of the network-forming type converter is high, the network-forming type converter is in weak power grid strength at the moment, and in order to guarantee the operation stability of a power grid system, the target network-forming type converter in the weak power grid strength is switched to be a network-following type converter.
That is, if the comprehensive participation factor C of the grid-type converter k is formed k Satisfies C k If the value is less than epsilon, epsilon represents a preset threshold value, and can be established by off-line simulation, the target network-constructing type converter is switched to a network-following type converter.
On the contrary, if the comprehensive participation factor C of the network type converter k is constructed k Does not satisfy C k If the number is less than epsilon, keeping the node to lay the target network-type converter unchanged.
In summary, the invention discloses a switching method of a converter operation mode, according to the actual power grid system topology, networking type converters are uniformly distributed on all new energy power source nodes, a simulation system formed by the distributed networking type converters is built, different faults are set at possible fault node positions of the simulation system, the power grid voltage drops, the faults are simulated, the corresponding relation between the transient power angle and the time of each networking type converter under each fault is obtained, the comprehensive participation factor of each networking type converter is determined based on the corresponding relation between the transient power angle and the time of each networking type converter under different faults, when the comprehensive participation factor is smaller than a preset threshold value, the interference degree of the networking type converter is high, the networking type converter is in weak power grid strength at the moment, in order to ensure the operation stability of the power grid system, the target networking type converter under the weak power strength is switched to a following networking type converter, and the switching of the converter operation mode is realized. The method is based on the solving idea of actual simulation and actual measurement of the disturbed track of the power grid system, considers the disturbed dynamic response characteristics of the network-forming type converter and the network-following type converter under different faults and is not the static characteristic under one working condition, and overcomes the defect of inaccuracy caused by guiding the operation mode switching of the converter only by means of the short-circuit ratio index representing the power frequency static characteristic of the rated working point in the prior art.
To further optimize the above embodiment, referring to fig. 2, a flowchart of a method for determining an integrated participation factor of each network type converter disclosed in the embodiment of the present invention, that is, step S104 specifically includes:
step S201, determining participation factors of each network type converter based on the corresponding relation between the transient power angle and the time of each network type converter under the condition of single fault;
the participation factor is used for representing the interference degree of the network type converter under a single fault.
The higher the value of the participation factor is, the weaker the interference degree of the network-type converter under the single fault is, and the network-type converter is in the strong power grid strength at the moment; on the contrary, the lower the value of the participation factor is, the stronger the interference degree of the network type converter under the single fault is, which indicates that the network type converter is in weak power grid strength at the moment.
Step S202, obtaining comprehensive participation factors of each network type converter based on corresponding participation factors of each network type converter under different faults and different fault occurrence probabilities.
The calculation formula of the comprehensive participation factor of each network type converter is as follows:
in the formula, C k Represents the integrated participation factor of the network type converter k and represents p F Representing the probability of occurrence of the fault F, c k.F And representing the corresponding participation factor of the network type converter k under the fault F.
To further optimize the above embodiment, referring to fig. 3, a flowchart of a method for determining a participation factor of each network type converter disclosed in the embodiment of the present invention, that is, step S201 specifically includes:
step S301, determining a first rotor angle of the network-type converter corresponding to a first moment in a mature period of the transient process and a second rotor angle of the network-type converter corresponding to a second moment based on a corresponding relation between a transient power angle and time corresponding to each network-type converter under a single fault;
wherein, the transient process mature period refers to: in the transient process, the rotor angle is relatively swung open to keep the state of the leading mode unchanged.
In practical applications, the corresponding relationship between the transient power angle and the time of the network-forming converter may be: transient power angle versus time curve, i.e. delta, for a network-forming converter i.F -a t-curve.
Wherein the first time and the second time are any two times in the transient process maturation period, such as the first time t 0 =8 τ, second time t 1 =9 τ, τ representing the fault clearing time, may take a value of 0.1s.
Determining a first moment t of each network type converter i in the maturation period of the transient process 0 Corresponding first rotor angle of network-forming type converter
And each network type converter i is at the second moment t in the mature period of the transient process 1 Corresponding second rotor angle of the net-forming type converter
Step S302, calculating a rotor angle difference between a second rotor angle of the network-forming type converter and a first rotor angle of the network-forming type converter corresponding to each network-forming type converter;
wherein the rotor angle difference delta i.F The calculation formula of (c) is as follows:
step S303, determining the participation factor of the target network-forming type converter with the highest rotor angle difference value as 1;
specifically, the network-forming type converters are sequenced according to the sequence of the numerical values of the rotor angular difference from large to small, the network-forming type converter with the first sequence is determined as the target network-forming type converter j with the highest numerical value of the rotor angular difference, and the participation factor c of the target network-forming type converter j is determined j.F ＝1。
And S304, determining participation factors of the network-type converters except the target network-type converter based on the target rotor angle difference corresponding to the target network-type converter.
Specifically, a quotient value of the rotor angle difference of each network type converter except the target network type converter and the target rotor angle difference is calculated, and the quotient value is determined as a participation factor of the corresponding network type converter.
That is, the calculation formula of the participation factor of each mesh type converter k except for the target mesh type converter is as follows:
in the formula, c k.F Representing the participation factor, Δ δ, of a network-type converter k j.F Represents a target rotor angle difference, delta, corresponding to the target network-forming type converter j k.F The rotor angle difference corresponding to the network type converter k is shown.
To further optimize the above embodiment, step S103 may specifically include:
and simulating the electromagnetic transient condition of each network type converter aiming at each fault to obtain the corresponding relation between the transient power angle and time of each network type converter under each fault, wherein the transient power angle is determined based on the output phase angle of the active loop of the network type converter and the phase angle of the power grid.
Specifically, for each fault, the electromagnetic transient situation of each network type converter is simulated based on electromagnetic transient simulation software (such as PSCAD), and a transient power angle-time (δ -t) curve of each network type converter under each fault is obtained.
Wherein the transient power angle δ is expressed as follows:
δ＝θ VSG -θ g ；
in the formula, theta VSG Representing the output phase angle theta of the active loop of the network-type converter g Representing the grid phase angle.
Corresponding to the embodiment of the method, the invention also discloses a switching device of the operation mode of the converter.
Referring to fig. 4, a schematic structural diagram of a switching device for an operating mode of a converter according to an embodiment of the present invention includes:
the simulation system building unit 401 is used for uniformly distributing networking type converters on all new energy power source nodes according to the actual power grid system topology and building a simulation system formed by the distributed networking type converters;
according to the embodiment, firstly, network-type converters are uniformly distributed on all new energy power source nodes according to the actual power grid system topology, and then a simulation system formed by the network-type converters is built in electromagnetic transient simulation software (such as PSCAD) according to the distributed network-type converters.
In practical application, each network-forming type converter may be a virtual synchronous machine, and the network-forming simulation parameters of each virtual synchronous machine may be the same or different, specifically according to actual needs, and the present invention is not limited herein.
A fault setting unit 402, configured to set different faults at each possible fault node of the simulation system, so as to drop a grid voltage;
wherein the possible fault node is determined according to the historical fault node.
In the embodiment, different faults are set at each possible fault node position of the simulation system, so that each possible fault node position is disturbed, and the voltage of the power grid drops.
In practical application, the positions of the possible fault nodes are set at the side of the alternating current system, the fault type is determined according to actual needs, for example, a symmetric short-circuit fault, and the fault clearing time τ can be uniformly set to 0.1s, and of course, the fault clearing time τ can also be set to other times as needed.
The simulation unit 403 is configured to simulate each fault, so as to obtain a corresponding relationship between a transient power angle and time of each networking type converter under each fault;
the corresponding relationship between the transient power angle and the time of the grid-structured converter may be a transient power angle-time (δ -t) curve.
A determining unit 404, configured to determine a comprehensive participation factor of each networking type converter based on a corresponding relationship between the transient power angle and time of each networking type converter under different faults;
the numerical value of the comprehensive participation factor is used for representing the interference degree of the network-structured converter under different faults. The higher the value of the comprehensive participation factor is, the weaker the interference degree of the network-structured type converter is, and the strong power network strength of the network-structured type converter is indicated; conversely, the lower the value of the comprehensive participation factor, the stronger the interference degree of the network-structured type converter is, which indicates that the network-structured type converter is in weak grid strength at this time.
The switching unit 405 is configured to switch the node position of the target network formation type converter where the comprehensive participation factor is smaller than the preset threshold value from the target network formation type converter to the network tracking type converter.
When the comprehensive participation factor is smaller than a preset threshold value, the interference degree of the network-forming type converter is high, the network-forming type converter is in weak power grid strength at the moment, and in order to guarantee the operation stability of a power grid system, the target network-forming type converter in the weak power grid strength is switched to be a network-following type converter.
That is, the integral participation factor C of the grid-type converter k k Satisfy C k If the current is less than epsilon, epsilon represents a preset threshold value, and can be established by off-line simulation, the target network-constructing type converter is switched to a network-following type converter.
In summary, the invention discloses a converter operation mode switching device, wherein grid-forming converters are uniformly distributed on all new energy power source nodes according to the actual power grid system topology, a simulation system formed by the distributed grid-forming converters is built, different faults are set at the positions of possible fault nodes of the simulation system, the voltage of a power grid drops, the faults are simulated, the corresponding relation between the transient power angle and the time of each grid-forming converter under each fault is obtained, the comprehensive participation factor of each grid-forming converter is determined based on the corresponding relation between the transient power angle and the time of each grid-forming converter under different faults, when the comprehensive participation factor is smaller than a preset threshold value, the interference degree of the grid-forming converter is high, the grid-forming converter is in weak power grid strength at the moment, and in order to ensure the operation stability of the power grid system, the target grid-forming converter under the weak power strength is switched to the grid-following converter, so that the converter operation mode switching is realized. The method is based on the solving idea of actual simulation and actual measurement of the disturbed track of the power grid system, considers the disturbed dynamic response characteristics of the network-forming type converter and the network-following type converter under different faults and is not the static characteristic under one working condition, and overcomes the defect of inaccuracy caused by guiding the operation mode switching of the converter only by means of the short-circuit ratio index representing the power frequency static characteristic of the rated working point in the prior art.
In order to further optimize the foregoing embodiment, referring to fig. 5, a schematic structural diagram of a determining unit disclosed in the embodiment of the present invention includes:
a participation factor determining subunit 501, configured to determine a participation factor of each networking type converter based on a corresponding relationship between the transient power angle and time corresponding to each networking type converter under a single fault;
the participation factor is used for representing the interference degree of the networking type converter under a single fault.
The higher the value of the participation factor is, the weaker the interference degree of the network-structured converter under the single fault is, and the network-structured converter is in the strong power grid strength at the moment; conversely, the lower the value of the participation factor, the stronger the interference degree of the network type converter under the single fault is, which indicates that the network type converter is in weak grid strength at this time.
The comprehensive participation factor determining subunit 502 is configured to obtain the comprehensive participation factor of each network type converter based on the corresponding participation factor of each network type converter under different faults and the occurrence probability of different faults.
The calculation formula of the comprehensive participation factor of each networking type converter is as follows:
in the formula, C k Represents the integrated participation factor of the network type converter k and represents p F Representing the probability of occurrence of a fault F, c k.F And representing the corresponding participation factor of the network type converter k under the fault F.
The participation factor determining subunit 501 may be specifically configured to:
determining a first rotor angle of the network type converter corresponding to a first moment in a mature period of the transient process and a second rotor angle of the network type converter corresponding to a second moment based on the corresponding relation between the transient power angle and time of each network type converter under a single fault, wherein the first moment and the second moment are any two moments in the mature period of the transient process;
calculating a rotor angle difference between a second rotor angle of the network type converter and a first rotor angle of the network type converter corresponding to each network type converter;
determining the participation factor of the target network-forming type converter with the highest rotor angular difference value as 1;
and determining the participation factors of the network-forming type converters except the target network-forming type converter based on the target rotor angle difference corresponding to the target network-forming type converter.
To further optimize the above embodiment, the participation factor determining subunit 501 may be further configured to:
and calculating a quotient value of the rotor angle difference of each network-type converter except the target network-type converter and the target rotor angle difference, and determining the quotient value as the participation factor of the corresponding network-type converter.
To further optimize the above embodiment, the simulation unit 403 may specifically be configured to:
and for each fault, simulating an electromagnetic transient situation of each networking type converter to obtain a corresponding relation between the transient power angle and time of each networking type converter under each fault, wherein the transient power angle is determined based on an output phase angle of an active loop of the networking type converter and a phase angle of a power grid.
Specifically, for each fault, an electromagnetic transient situation of each grid-type converter is simulated based on electromagnetic transient simulation software (such as PSCAD), and a transient power angle-time (δ -t) curve of each grid-type converter under each fault is obtained.
Wherein the transient power angle δ is expressed as follows:
δ＝θ VSG -θ g ；
in the formula, theta VSG Representing the output phase angle theta of the active loop of the network-type converter g Representing the grid phase angle.
It should be noted that, for the specific working principle of each component in the device embodiment, please refer to the corresponding part of the method embodiment, which is not described herein again.
Finally, it should also be noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising a," "8230," "8230," or "comprising" does not exclude the presence of additional like elements in a process, method, article, or apparatus that comprises the element.
In the present specification, the embodiments are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (12)
1. A method for switching the operation modes of a converter is characterized by comprising the following steps:
according to the actual power grid system topology, network-forming type converters are uniformly distributed on all new energy power source nodes, and a simulation system formed by the distributed network-forming type converters is built;
different faults are set at each possible fault node position of the simulation system, so that the voltage of the power grid drops;
simulating each fault to obtain the corresponding relation between the transient power angle and the time of each networking type converter under each fault;
determining a comprehensive participation factor of each networking type converter based on the corresponding relation between the transient power angle and the time of each networking type converter under different faults, wherein the numerical value of the comprehensive participation factor is used for representing the interference degree of the networking type converter under different faults;
and switching the node position of the target network-forming type converter with the comprehensive participation factor smaller than a preset threshold value into a network-following type converter by the target network-forming type converter.
2. The switching method according to claim 1, wherein the determining a comprehensive participation factor of each of the network type converters based on the corresponding relationship between the transient power angle and time of each of the network type converters under different faults comprises:
determining participation factors of each networking type converter based on the corresponding relation between the transient state power angle and the time of each networking type converter under the condition of single fault, wherein the participation factors are used for representing the interference degree of the networking type converter under the condition of single fault;
and obtaining the comprehensive participation factor of each network-forming type converter based on the corresponding participation factor of each network-forming type converter under different faults and the occurrence probability of different faults.
3. The switching method according to claim 2, wherein the determining the participation factor of each grid-type converter based on the transient power angle and time correspondence relationship of each grid-type converter under a single fault comprises:
determining a first rotor angle of the network-structured converter corresponding to a first moment in a mature period of the transient process and a second rotor angle of the network-structured converter corresponding to a second moment based on the corresponding relation between the transient power angle and time of each network-structured converter corresponding to a single fault, wherein the first moment and the second moment are any two moments in the mature period of the transient process;
calculating a rotor angle difference between a second rotor angle of the network type converter and a first rotor angle of the network type converter corresponding to each network type converter;
determining the participation factor of the target network-forming type converter with the highest rotor angular difference value as 1;
and determining the participation factors of the network type transformers except the target network type transformer based on the target rotor angle difference corresponding to the target network type transformer.
4. The switching method according to claim 3, wherein the determining the participation factor of each of the network type converters other than the target network type converter based on the target rotor angle difference corresponding to the target network type converter comprises:
and calculating a quotient value of the rotor angle difference of each network-type converter except the target network-type converter and the target rotor angle difference, and determining the quotient value as the participation factor of the corresponding network-type converter.
5. The switching method according to claim 1, wherein each grid-connected converter is a virtual synchronous machine, and grid-connected simulation parameters of each virtual synchronous machine are the same or different.
6. The switching method according to claim 1, wherein each of the possible fault node locations is provided on an ac system side.
7. The switching method according to claim 1, wherein the simulating each fault to obtain a corresponding relationship between a transient power angle and time of each of the network type converters under each fault includes:
and simulating the electromagnetic transient condition of each networking type converter aiming at each fault to obtain the corresponding relation between the transient power angle and time of each networking type converter under each fault, wherein the transient power angle is determined based on the active loop output phase angle and the grid phase angle of the networking type converter.
8. A converter operating mode switching device, comprising:
the simulation system building unit is used for uniformly distributing networking type converters on all new energy power supply nodes according to the actual power grid system topology and building a simulation system formed by the distributed networking type converters;
the fault setting unit is used for setting different faults at each possible fault node position of the simulation system so as to drop the voltage of the power grid;
the simulation unit is used for simulating each fault to obtain the corresponding relation between the transient power angle and the time of each networking type converter under each fault;
the determining unit is configured to determine a comprehensive participation factor of each networking type converter based on a corresponding relationship between the transient power angle and time of each networking type converter under different faults, where a numerical value of the comprehensive participation factor is used to represent a degree of interference of the networking type converter under different faults;
and the switching unit is used for switching the node position of the target network-forming type converter with the comprehensive participation factor smaller than a preset threshold value into the network-following type converter by the target network-forming type converter.
9. The switching apparatus according to claim 8, wherein the determining unit includes:
the participation factor determining subunit is configured to determine a participation factor of each networking type converter based on a corresponding relationship between the transient power angle and time, corresponding to each networking type converter under a single fault, where the participation factor is used to characterize an interference degree of the networking type converter under the single fault;
and the comprehensive participation factor determining subunit is used for obtaining the comprehensive participation factor of each networking type converter based on the corresponding participation factor of each networking type converter under different faults and the occurrence probability of different faults.
10. The switching device according to claim 9, wherein the participation factor determining subunit is specifically configured to:
determining a first rotor angle of the network type converter corresponding to a first moment in a mature period of the transient process and a second rotor angle of the network type converter corresponding to a second moment based on the corresponding relation between the transient power angle and time of each network type converter under a single fault, wherein the first moment and the second moment are any two moments in the mature period of the transient process;
calculating a rotor angle difference between a second rotor angle of the network type converter and a first rotor angle of the network type converter corresponding to each network type converter;
determining the participation factor of the target network-forming type converter with the highest rotor angular difference value as 1;
and determining the participation factors of the network-forming type converters except the target network-forming type converter based on the target rotor angle difference corresponding to the target network-forming type converter.
11. The switching device according to claim 10, wherein the participation factor determining subunit is further configured to:
and calculating a quotient value of the rotor angle difference of each network-type converter except the target network-type converter and the target rotor angle difference, and determining the quotient value as the participation factor of the corresponding network-type converter.
12. The switching device according to claim 8, wherein the emulation unit is specifically configured to:
and simulating the electromagnetic transient condition of each networking type converter aiming at each fault to obtain the corresponding relation between the transient power angle and time of each networking type converter under each fault, wherein the transient power angle is determined based on the active loop output phase angle and the grid phase angle of the networking type converter.
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| CN117791716A (en) * | 2024-02-28 | 2024-03-29 | 国网江西省电力有限公司电力科学研究院 | New energy synchronous stabilization and dynamic voltage support security domain modeling method and system |
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| CN117791716A (en) * | 2024-02-28 | 2024-03-29 | 国网江西省电力有限公司电力科学研究院 | New energy synchronous stabilization and dynamic voltage support security domain modeling method and system |
| CN117791716B (en) * | 2024-02-28 | 2024-06-04 | 国网江西省电力有限公司电力科学研究院 | New energy synchronous stabilization and dynamic voltage support security domain modeling method and system |
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