A method and apparatus for switching operating modes of a power converter

Abstract

The application discloses a kind of switching methods of converter operating mode, according to actual power grid system topology, all new energy power supply nodes are evenly distributed network type converter, and corresponding simulation system is built, different faults are set in each possible fault node position of simulation system to make grid voltage drop, simulate each fault, obtain the transient power angle of each network type converter and the corresponding relationship of time under each fault, determine the comprehensive participation factor of each network type converter based on the corresponding relationship under each fault, the node position of target network type converter with comprehensive participation factor less than preset threshold is switched to network type converter by target network type converter.The application is based on the solution idea of actual power grid system disturbed trajectory simulation measurement, considers the disturbed dynamic response characteristics of network type converter and network type converter under different faults, overcomes the inaccuracy caused by short-circuit ratio index in prior art to guide converter operating mode switching.

Description

Technical Field

[0001] This invention relates to the field of converter technology, and more specifically, to a method and apparatus for switching converter operating modes. Background Technology

[0002] Based on different control strategies, voltage source converters can be categorized into grid-connected converters and grid-connected converters. Grid-connected converters utilize phase-locked loops (PLLs) to achieve synchronization with the AC grid. They follow the voltage of the connected AC bus and inject a set current to achieve the power generation target, ensuring grid system stability under high grid intensity. However, because grid-connected converters lack the power and power angle equation constraints of synchronous motors and do not have instantaneous power sharing capabilities, they introduce more negative damping under weak grid intensity, which is detrimental to improving grid system stability. Grid-connected converters generally use power control to achieve synchronization while simultaneously regulating power. The DC side of grid-connected converters is equipped with energy storage units to provide additional power support during dynamic processes. By integrating the synchronization function into the power controller, grid-connected converters overcome the shortcomings of PLLs, enabling them to maintain grid system stability even under weak grid intensity, thus solving the problems encountered by grid-connected converters under weak grid intensity. However, grid-type converters are not conducive to improving the stability of the power grid system under strong grid intensity.

[0003] To address the characteristics of grid-connected converters and grid-connected converters in terms of grid system stability under different grid strengths, existing methods for switching voltage source converters involve switching between grid-connected and grid-connected converters based on the equivalent short-circuit ratio of the grid system, in order to maintain the operational stability of the grid system.

[0004] However, the equivalent short-circuit ratio only considers the static characteristics of the power frequency at the rated operating point and cannot reflect the influence of the dynamic characteristics and output characteristics of each control loop in the converter. As a result, the switching of the existing converter operating mode cannot reflect the actual power grid topology and cannot guarantee the stability of the power grid system. Summary of the Invention

[0005] In view of this, the present invention discloses a method and apparatus for switching the operating mode of a converter, so as to realize the solution based on the simulation and measurement of the disturbance trajectory of the actual power grid system, and consider the dynamic response characteristics of grid-connected converters and grid-linked converters under different faults. This overcomes the inaccuracy caused by relying solely on the short-circuit ratio index, which characterizes the static characteristics of the rated operating point at the power frequency, to guide the switching of the converter operating mode in the prior art.

[0006] A method for switching the operating mode of a converter, comprising:

[0007] Based on the actual power grid system topology, grid-type converters are deployed at all new energy power nodes, and a simulation system composed of the deployed grid-type converters is built.

[0008] Different faults are set at each possible fault node location in the simulation system to cause the grid voltage to drop.

[0009] Simulate each of the aforementioned faults to obtain the transient power angle versus time relationship of each grid-type converter under each fault.

[0010] Based on the transient power angle and time correspondence of each grid-type converter under different faults, the comprehensive participation factor of each grid-type converter is determined, wherein the magnitude of the comprehensive participation factor is used to characterize the degree of disturbance of the grid-type converter under different faults.

[0011] The node where the target grid-type converter is located, whose comprehensive participation factor is less than a preset threshold, is switched from the target grid-type converter to a grid-following converter.

[0012] Optionally, determining the comprehensive participation factor for each grid-type converter based on the transient power angle versus time correspondence under different fault conditions includes:

[0013] Based on the transient power angle and time correspondence of each grid-type converter under a single fault, the participation factor of each grid-type converter is determined, wherein the participation factor is used to characterize the degree of disturbance of the grid-type converter under a single fault.

[0014] Based on the participation factor corresponding to each grid-type converter under different fault conditions and the probability of different fault occurrences, the comprehensive participation factor of each grid-type converter is obtained.

[0015] Optionally, determining the participation factor for each grid-type converter based on the transient power angle versus time correspondence under a single fault includes:

[0016] Based on the transient power angle and time correspondence of each grid-type converter under a single fault, the first rotor angle of the grid-type converter corresponding to the first moment of the transient process maturity period and the second rotor angle of the grid-type converter corresponding to the second moment are determined, wherein the first moment and the second moment are any two moments in the transient process maturity period.

[0017] Calculate the rotor angle difference between the second rotor angle and the first rotor angle of the grid converter corresponding to each of the grid converters;

[0018] The participation factor of the target grid-type converter with the highest rotor angle difference value is set to 1;

[0019] The participation factor of each of the network converters other than the target network converter is determined based on the target rotor angle difference corresponding to the target network converter.

[0020] Optionally, determining the participation factor for each of the network converters other than the target network converter based on the target rotor angle difference corresponding to the target network converter includes:

[0021] Calculate the quotient of the rotor angle difference of each of the grid-type converters other than the target grid-type converter with respect to the target rotor angle difference, and determine the quotient as the participation factor of the corresponding grid-type converter.

[0022] Optionally, each of the grid-type converters is a virtual synchronous machine, and the grid-connected simulation parameters of each virtual synchronous machine may be the same or different.

[0023] Optionally, the locations of each of the potential fault nodes are set on the AC system side.

[0024] Optionally, the simulation of each of the aforementioned faults yields the transient power angle versus time relationship for each grid-type converter under each fault, including:

[0025] For each of the aforementioned faults, the electromagnetic transient conditions of each of the grid-type converters are simulated to obtain the transient power angle and time correspondence of each of the grid-type converters under each fault. The transient power angle is determined based on the active power loop output phase angle of the grid-type converter and the grid phase angle.

[0026] A converter operating mode switching device, comprising:

[0027] The simulation system building unit is used to deploy grid-type converters at all new energy power nodes according to the actual power grid system topology, and build a simulation system composed of the deployed grid-type converters.

[0028] The fault setting unit is used to set different faults at each possible fault node location in the simulation system to cause the grid voltage to drop.

[0029] The simulation unit is used to simulate each of the aforementioned faults and obtain the transient power angle and time correspondence of each grid-type converter under each of the aforementioned faults.

[0030] The determining unit is used to determine the comprehensive participation factor of each grid-type converter based on the transient power angle and time correspondence of each grid-type converter under different faults, wherein the value of the comprehensive participation factor is used to characterize the degree of disturbance of the grid-type converter under different faults.

[0031] The switching unit is used to switch the node location of the target grid-type converter, where the comprehensive participation factor is less than a preset threshold, from the target grid-type converter to a grid-following converter.

[0032] Optionally, the determining unit includes:

[0033] The participation factor determination subunit is used to determine the participation factor of each grid-type converter based on the transient power angle and time correspondence of each grid-type converter under a single fault, wherein the participation factor is used to characterize the degree of disturbance of the grid-type converter under a single fault.

[0034] The comprehensive participation factor determination subunit is used to obtain the comprehensive participation factor of each grid-type converter based on the participation factor corresponding to each grid-type converter under different faults and the probability of different fault occurrences.

[0035] Optionally, the participation factor determination subunit is specifically used for:

[0036] Based on the transient power angle and time correspondence of each grid-type converter under a single fault, the first rotor angle of the grid-type converter corresponding to the first moment of the transient process maturity period and the second rotor angle of the grid-type converter corresponding to the second moment are determined, wherein the first moment and the second moment are any two moments in the transient process maturity period.

[0037] Calculate the rotor angle difference between the second rotor angle and the first rotor angle of the grid converter corresponding to each of the grid converters;

[0038] The participation factor of the target grid-type converter with the highest rotor angle difference value is set to 1;

[0039] The participation factor of each of the network converters other than the target network converter is determined based on the target rotor angle difference corresponding to the target network converter.

[0040] Optionally, the participation factor determination subunit is further used for:

[0041] Calculate the quotient of the rotor angle difference of each of the grid-type converters other than the target grid-type converter with respect to the target rotor angle difference, and determine the quotient as the participation factor of the corresponding grid-type converter.

[0042] Optionally, the simulation unit is specifically used for:

[0043] For each of the aforementioned faults, the electromagnetic transient conditions of each of the grid-type converters are simulated to obtain the transient power angle and time correspondence of each of the grid-type converters under each fault. The transient power angle is determined based on the active power loop output phase angle of the grid-type converter and the grid phase angle.

[0044] As can be seen from the above technical solution, the present invention discloses a method and device for switching the operating mode of a converter. The method includes: according to the actual power grid system topology, deploying grid-type converters at all new energy power nodes, and building a simulation system composed of the deployed grid-type converters; setting different faults at each possible fault node location in the simulation system to cause the grid voltage to drop; simulating each fault to obtain the transient power angle and time correspondence of each grid-type converter under each fault; determining the comprehensive participation factor of each grid-type converter based on the transient power angle and time correspondence of each grid-type converter under different faults; when the comprehensive participation factor is less than a preset threshold, it indicates that the grid-type converter is highly susceptible to interference, indicating that the grid-type converter is under weak grid strength; to ensure the stability of the power grid system operation, the target grid-type converter under weak grid strength is switched to a grid-following converter, thereby realizing the switching of the converter operating mode. This invention is based on the solution approach of simulation and measurement of the disturbance trajectory of actual power grid system. It considers the dynamic response characteristics of grid-connected converters and grid-linked converters under different faults, rather than the static characteristics under a single operating condition. This overcomes the inaccuracy caused by relying solely on the short-circuit ratio index, which characterizes the static characteristics at the rated operating point, to guide the switching of converter operating modes in the existing technology. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the published drawings without creative effort.

[0046] Figure 1 This is a flowchart of a converter operation mode switching method disclosed in an embodiment of the present invention;

[0047] Figure 2 This is a flowchart illustrating a method for determining the comprehensive participation factor of each grid-type converter, as disclosed in an embodiment of the present invention.

[0048] Figure 3 This is a flowchart of a method for determining the participation factor of each grid-type converter, as disclosed in an embodiment of the present invention.

[0049] Figure 4 This is a schematic diagram of the structure of a converter operation mode switching device disclosed in an embodiment of the present invention;

[0050] Figure 5 This is a schematic diagram of the structure of a determining unit disclosed in an embodiment of the present invention. Detailed Implementation

[0051] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] This invention discloses a method and apparatus for switching converter operating modes. The method includes: deploying grid-type converters at all new energy power nodes according to the actual power grid system topology, and building a simulation system composed of the deployed grid-type converters. Different faults are set at the possible fault nodes of the simulation system to cause the grid voltage to drop. The simulation is performed to obtain the transient power angle and time correspondence of each grid-type converter under each fault. Based on the transient power angle and time correspondence of each grid-type converter under different faults, the comprehensive participation factor of each grid-type converter is determined. When the comprehensive participation factor is less than a preset threshold, it indicates that the grid-type converter is highly susceptible to interference, indicating that the grid-type converter is under weak grid strength. In order to ensure the stability of the power grid system operation, the target grid-type converter under weak grid strength is switched to a grid-following converter, thereby realizing the switching of converter operating modes. This invention is based on the solution approach of simulation and measurement of the disturbance trajectory of actual power grid system. It considers the dynamic response characteristics of grid-connected converters and grid-linked converters under different faults, rather than the static characteristics under a single operating condition. This overcomes the inaccuracy caused by relying solely on the short-circuit ratio index, which characterizes the static characteristics at the rated operating point, to guide the switching of converter operating modes in the existing technology.

[0053] See Figure 1 The present invention discloses a flowchart of a method for switching the operating mode of a converter, the method comprising:

[0054] Step S101: Based on the actual power grid system topology, deploy grid-type converters at all new energy power nodes and build a simulation system composed of the deployed grid-type converters.

[0055] This embodiment first deploys grid-type converters at all new energy power nodes according to the actual power grid system topology. Then, based on the deployed grid-type converters, a simulation system composed of grid-type converters is built in electromagnetic transient simulation software (such as PSCAD).

[0056] In practical applications, each grid-type converter can be a virtual synchronous machine. The grid-connected simulation parameters of each virtual synchronous machine can be the same or different, depending on the actual needs. This invention does not impose any limitations on this.

[0057] Step S102: Set different faults at each possible fault node location in the simulation system to cause the grid voltage to drop;

[0058] Among them, the potential fault nodes are determined based on historical fault nodes.

[0059] This embodiment sets different faults at each possible fault node location in the simulation system, thereby applying a disturbance to each possible fault node location and causing the grid voltage to drop.

[0060] In practical applications, the locations of each possible fault node are set on the AC system side, and the fault type is determined according to actual needs. For example, for a symmetrical short circuit fault, the fault clearing time τ can be uniformly set to 0.1s. Of course, the fault clearing time τ can also be set to other times as needed.

[0061] Step S103: Simulate each fault to obtain the transient power angle and time correspondence of each grid-type converter under each fault;

[0062] Specifically, the relationship between the transient power angle and time of a grid-type converter can be represented as a transient power angle-time (δ-t) curve.

[0063] Step S104: Based on the transient power angle and time correspondence of each grid-type converter under different fault conditions, determine the comprehensive participation factor of each grid-type converter;

[0064] The magnitude of the comprehensive participation factor is used to characterize the degree of disturbance experienced by the grid-type converter under different fault conditions. A higher comprehensive participation factor indicates a weaker degree of disturbance to the grid-type converter, suggesting that the converter is under strong grid strength. Conversely, a lower comprehensive participation factor indicates a stronger degree of disturbance to the grid-type converter, suggesting that the converter is under weak grid strength.

[0065] Step S105: Switch the node location of the target grid-type converter, where the comprehensive participation factor is less than the preset threshold, from the target grid-type converter to the grid-type converter.

[0066] When the comprehensive participation factor is less than the preset threshold, it indicates that the grid-type converter is highly susceptible to interference, meaning that the grid-type converter is under weak grid strength. In order to ensure the stability of the power grid system, the target grid-type converter under weak grid strength will be switched to a grid-connected converter.

[0067] In other words, if the comprehensive participation factor C of the grid-type converter k is... k Satisfy C k When <ε, ε represents a preset threshold, which can be determined by offline simulation, the target grid-type converter will be switched to a follow-grid type converter.

[0068] Conversely, if the comprehensive participation factor C of the grid-type converter k is... k Not satisfied with C k When ε < ε, the target grid-type converter at that node remains unchanged.

[0069] In summary, this invention discloses a method for switching converter operating modes. Based on the actual power grid topology, grid-type converters are deployed at all new energy power nodes, and a simulation system composed of the deployed grid-type converters is built. Different faults are set at the possible fault locations of the simulation system to cause the grid voltage to drop. The simulation of each fault is performed to obtain the transient power angle and time correspondence of each grid-type converter under each fault. Based on the transient power angle and time correspondence of each grid-type converter under different faults, the comprehensive participation factor of each grid-type converter is determined. When the comprehensive participation factor is less than a preset threshold, it indicates that the grid-type converter is highly susceptible to interference, indicating that the grid-type converter is under weak grid strength. To ensure the stability of the power grid system, the target grid-type converter under weak grid strength is switched to a grid-following converter, thereby realizing the switching of the converter operating mode. This invention is based on the solution approach of simulation and measurement of the disturbance trajectory of actual power grid system. It considers the dynamic response characteristics of grid-connected converters and grid-linked converters under different faults, rather than the static characteristics under a single operating condition. This overcomes the inaccuracy caused by relying solely on the short-circuit ratio index, which characterizes the static characteristics at the rated operating point, to guide the switching of converter operating modes in the existing technology.

[0070] To further optimize the above embodiments, see [link to relevant documentation]. Figure 2 The flowchart of a method for determining the comprehensive participation factor of each grid-type converter disclosed in this embodiment of the invention, specifically step S104, includes:

[0071] Step S201: Based on the transient power angle and time correspondence of each grid-type converter under a single fault, determine the participation factor of each grid-type converter;

[0072] Among them, the participation factor is used to characterize the degree of disturbance to the grid-type converter under a single fault.

[0073] The higher the value of the participation factor, the weaker the disturbance of the grid-type converter under a single fault, indicating that the grid-type converter is under strong grid strength at this time; conversely, the lower the value of the participation factor, the stronger the disturbance of the grid-type converter under a single fault, indicating that the grid-type converter is under weak grid strength at this time.

[0074] Step S202: Based on the participation factors of each grid-type converter under different fault conditions and the probability of different fault occurrences, obtain the comprehensive participation factor of each grid-type converter.

[0075] The formula for calculating the overall participation factor of each grid-type converter is as follows:

[0076]

[0077] In the formula, C k The comprehensive participation factor of grid-type converter k is represented by p. F c represents the probability of fault F occurring. k.F This represents the participation factor of the grid-type converter k under fault F.

[0078] To further optimize the above embodiments, see [link to relevant documentation]. Figure 3 The flowchart of a method for determining the participation factor of each grid-type converter disclosed in this embodiment of the invention, specifically step S201 includes:

[0079] Step S301: Based on the correspondence between the transient power angle and time of each grid-type converter under a single fault, determine the first rotor angle of the grid-type converter at the first moment of the transient process maturity period, and the second rotor angle of the grid-type converter at the second moment.

[0080] The transient process maturity period refers to the state in which the rotor angle relative swing-off dominant mode remains unchanged during the transient process.

[0081] In practical applications, the transient power angle of a grid-type converter corresponds to time as follows: the transient power angle versus time curve of the grid-type converter, i.e., δ i.F -t curve.

[0082] Here, the first time and the second time are any two times in the maturity period of the transient process. For example, the first time t0 = 8τ and the second time t1 = 9τ, where τ represents the fault clearing time and can be 0.1s.

[0083] Determine the first rotor angle of each grid-type converter i at the first moment t0 during the transient process maturity period. And the second rotor angle of each grid-type converter i at the second time t1 during the transient process maturity period.

[0084] Step S302: Calculate the rotor angle difference between the second rotor angle and the first rotor angle of the grid-type converter for each grid-type converter;

[0085] Wherein, rotor angle difference Δδ i.F The calculation formula is as follows:

[0086]

[0087] Step S303: Set the participation factor of the target grid-type converter with the highest rotor angle difference value to 1;

[0088] Specifically, the various grid-type converters are sorted in descending order of rotor angle difference value. The grid-type converter ranked first is determined as the target grid-type converter j with the highest rotor angle difference value. Then, the participation factor c of the target grid-type converter j is... j.F =1.

[0089] Step S304: Determine the participation factors of each grid-type converter other than the target grid-type converter based on the target rotor angle difference corresponding to the target grid-type converter.

[0090] Specifically, the quotient of the rotor angle difference of each grid converter other than the target grid converter is calculated and the target rotor angle difference is determined as the participation factor of the corresponding grid converter.

[0091] In other words, the formula for calculating the participation factor of each grid-type converter k, excluding the target grid-type converter, is as follows:

[0092]

[0093] In the formula, c k.F Δδ represents the participation factor of grid-type converter k. j.F Δδ represents the target rotor angle difference corresponding to the target grid-type converter j. k.F This represents the rotor angle difference corresponding to k in a grid-type converter.

[0094] To further optimize the above embodiments, step S103 may specifically include:

[0095] For each fault, the electromagnetic transient situation of each grid-type converter is simulated to obtain the transient power angle and time correspondence of each grid-type converter under each fault. The transient power angle is determined based on the active power loop output phase angle of the grid-type converter and the grid phase angle.

[0096] Specifically, for each fault, the electromagnetic transient conditions of each grid-type converter are simulated using electromagnetic transient simulation software (such as PSCAD) to obtain the transient power angle-time (δ-t) curves of each grid-type converter under each fault.

[0097] The expression for the transient work angle δ is as follows:

[0098] δ=θ VSG -θ g ;

[0099] In the formula, θ VSG θ represents the active loop output phase angle of a grid-connected converter. g This indicates the phase angle of the power grid.

[0100] Corresponding to the above method embodiments, the present invention also discloses a converter operating mode switching device.

[0101] See Figure 4 A schematic diagram of a converter operation mode switching device disclosed in an embodiment of the present invention is shown. The device includes:

[0102] The simulation system building unit 401 is used to deploy grid-type converters at all new energy power nodes according to the actual power grid system topology, and build a simulation system composed of the deployed grid-type converters.

[0103] This embodiment first deploys grid-type converters at all new energy power nodes according to the actual power grid system topology. Then, based on the deployed grid-type converters, a simulation system composed of grid-type converters is built in electromagnetic transient simulation software (such as PSCAD).

[0104] In practical applications, each grid-type converter can be a virtual synchronous machine. The grid-connected simulation parameters of each virtual synchronous machine can be the same or different, depending on the actual needs. This invention does not impose any limitations on this.

[0105] The fault setting unit 402 is used to set different faults at each possible fault node location in the simulation system to cause the grid voltage to drop.

[0106] Among them, the potential fault nodes are determined based on historical fault nodes.

[0107] This embodiment sets different faults at each possible fault node location in the simulation system, thereby applying a disturbance to each possible fault node location and causing the grid voltage to drop.

[0108] In practical applications, the locations of each possible fault node are set on the AC system side, and the fault type is determined according to actual needs. For example, for a symmetrical short circuit fault, the fault clearing time τ can be uniformly set to 0.1s. Of course, the fault clearing time τ can also be set to other times as needed.

[0109] Simulation unit 403 is used to simulate each of the aforementioned faults and obtain the transient power angle and time correspondence of each of the grid-type converters under each of the aforementioned faults;

[0110] Specifically, the relationship between the transient power angle and time of a grid-type converter can be represented as a transient power angle-time (δ-t) curve.

[0111] The determining unit 404 is used to determine the comprehensive participation factor of each grid-type converter based on the transient power angle and time correspondence of each grid-type converter under different fault conditions;

[0112] The comprehensive participation factor is used to characterize the degree of disturbance to the grid-type converter under different fault conditions. The higher the comprehensive participation factor value, the weaker the disturbance to the grid-type converter, indicating that the grid-type converter is under strong grid strength; conversely, the lower the comprehensive participation factor value, the stronger the disturbance to the grid-type converter, indicating that the grid-type converter is under weak grid strength.

[0113] The switching unit 405 is used to switch the node location of the target grid-type converter, where the comprehensive participation factor is less than a preset threshold, from the target grid-type converter to a grid-type converter.

[0114] When the comprehensive participation factor is less than the preset threshold, it indicates that the grid-type converter is highly susceptible to interference, meaning that the grid-type converter is under weak grid strength. In order to ensure the stability of the power grid system, the target grid-type converter under weak grid strength will be switched to a grid-connected converter.

[0115] In other words, if the comprehensive participation factor C of the grid-type converter k is... k Satisfy C k When <ε, ε represents a preset threshold, which can be determined by offline simulation, the target grid-type converter will be switched to a follow-grid type converter.

[0116] In summary, this invention discloses a converter operation mode switching device. Based on the actual power grid topology, grid-type converters are deployed at all new energy power nodes, and a simulation system composed of the deployed grid-type converters is built. Different faults are set at the possible fault nodes of the simulation system to cause the grid voltage to drop. The simulation of each fault is performed to obtain the transient power angle and time correspondence of each grid-type converter under each fault. Based on the transient power angle and time correspondence of each grid-type converter under different faults, the comprehensive participation factor of each grid-type converter is determined. When the comprehensive participation factor is less than a preset threshold, it indicates that the grid-type converter is highly susceptible to interference, indicating that the grid-type converter is under weak grid strength. In order to ensure the stability of the power grid system operation, the target grid-type converter under weak grid strength is switched to a grid-following converter, thereby realizing the switching of the converter operation mode. This invention is based on the solution approach of simulation and measurement of the disturbance trajectory of actual power grid system. It considers the dynamic response characteristics of grid-connected converters and grid-linked converters under different faults, rather than the static characteristics under a single operating condition. This overcomes the inaccuracy caused by relying solely on the short-circuit ratio index, which characterizes the static characteristics at the rated operating point, to guide the switching of converter operating modes in the existing technology.

[0117] To further optimize the above embodiments, see [link to relevant documentation]. Figure 5 The present invention discloses a structural schematic diagram of a determining unit, the determining unit comprising:

[0118] The participation factor determination subunit 501 is used to determine the participation factor of each grid-type converter based on the transient power angle and time correspondence of each grid-type converter under a single fault.

[0119] Among them, the participation factor is used to characterize the degree of disturbance to the grid-type converter under a single fault.

[0120] The higher the value of the participation factor, the weaker the disturbance of the grid-type converter under a single fault, indicating that the grid-type converter is under strong grid strength at this time; conversely, the lower the value of the participation factor, the stronger the disturbance of the grid-type converter under a single fault, indicating that the grid-type converter is under weak grid strength at this time.

[0121] The comprehensive participation factor determination subunit 502 is used to obtain the comprehensive participation factor of each grid-type converter based on the participation factor corresponding to each grid-type converter under different faults and the probability of different fault occurrences.

[0122] The formula for calculating the overall participation factor of each grid-type converter is as follows:

[0123]

[0124] In the formula, Ck The comprehensive participation factor of grid-type converter k is represented by p. F c represents the probability of fault F occurring. k.F This represents the participation factor of the grid-type converter k under fault F.

[0125] Specifically, the participation factor determination subunit 501 can be used for:

[0126] Based on the transient power angle and time correspondence of each grid-type converter under a single fault, the first rotor angle of the grid-type converter corresponding to the first moment of the transient process maturity period and the second rotor angle of the grid-type converter corresponding to the second moment are determined, wherein the first moment and the second moment are any two moments in the transient process maturity period.

[0127] Calculate the rotor angle difference between the second rotor angle and the first rotor angle of the grid converter corresponding to each of the grid converters;

[0128] The participation factor of the target grid-type converter with the highest rotor angle difference value is set to 1;

[0129] The participation factor of each of the network converters other than the target network converter is determined based on the target rotor angle difference corresponding to the target network converter.

[0130] To further optimize the above embodiments, the participation factor determination subunit 501 can also be used for:

[0131] Calculate the quotient of the rotor angle difference of each of the grid-type converters other than the target grid-type converter with respect to the target rotor angle difference, and determine the quotient as the participation factor of the corresponding grid-type converter.

[0132] To further optimize the above embodiments, the simulation unit 403 can specifically be used for:

[0133] For each of the aforementioned faults, the electromagnetic transient conditions of each of the grid-type converters are simulated to obtain the transient power angle and time correspondence of each of the grid-type converters under each fault. The transient power angle is determined based on the active power loop output phase angle of the grid-type converter and the grid phase angle.

[0134] Specifically, for each fault, the electromagnetic transient conditions of each grid-type converter are simulated using electromagnetic transient simulation software (such as PSCAD) to obtain the transient power angle-time (δ-t) curves of each grid-type converter under each fault.

[0135] The expression for the transient work angle δ is as follows:

[0136] δ=θVSG -θ g ;

[0137] In the formula, θ VSG θ represents the active loop output phase angle of a grid-connected converter. g This indicates the phase angle of the power grid.

[0138] It should be noted that the specific working principles of each component in the device embodiment can be found in the corresponding section of the method embodiment, and will not be repeated here.

[0139] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0140] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0141] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not 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

1. A method for switching the operating mode of a converter, characterized in that, include: Based on the actual power grid system topology, grid-type converters are deployed at all new energy power nodes, and a simulation system composed of the deployed grid-type converters is built. Different faults are set at each possible fault node location in the simulation system to cause the grid voltage to drop. Simulate each of the aforementioned faults to obtain the transient power angle versus time relationship of each grid-type converter under each fault. Based on the transient power angle and time correspondence of each grid-type converter under different faults, the comprehensive participation factor of each grid-type converter is determined, wherein the magnitude of the comprehensive participation factor is used to characterize the degree of disturbance of the grid-type converter under different faults. The node location of the target grid-type converter, where the comprehensive participation factor is less than a preset threshold, is switched from the target grid-type converter to a grid-following converter; The determination of the comprehensive participation factor for each grid-connected converter based on the transient power angle versus time correspondence under different fault conditions includes: Based on the transient power angle and time correspondence of each grid-type converter under a single fault, the participation factor of each grid-type converter is determined, wherein the participation factor is used to characterize the degree of disturbance of the grid-type converter under a single fault. Based on the participation factor corresponding to each grid-type converter under different fault conditions and the probability of different fault occurrences, the comprehensive participation factor of each grid-type converter is obtained.

2. The switching method according to claim 1, characterized in that, The determination of the participation factor for each grid-type converter based on the transient power angle versus time correspondence under a single fault includes: Based on the transient power angle and time correspondence of each grid-type converter under a single fault, the first rotor angle of the grid-type converter corresponding to the first moment of the transient process maturity period and the second rotor angle of the grid-type converter corresponding to the second moment are determined, wherein the first moment and the second moment are any two moments in the transient process maturity period. Calculate the rotor angle difference between the second rotor angle and the first rotor angle of the grid converter corresponding to each of the grid converters; The participation factor of the target grid-type converter with the highest rotor angle difference value is set to 1; The participation factor of each of the network converters other than the target network converter is determined based on the target rotor angle difference corresponding to the target network converter.

3. The switching method according to claim 2, characterized in that, The determination of the participation factor for each of the network converters other than the target network converter based on the target rotor angle difference corresponding to the target network converter includes: Calculate the quotient of the rotor angle difference of each of the grid-type converters other than the target grid-type converter with respect to the target rotor angle difference, and determine the quotient as the participation factor of the corresponding grid-type converter.

4. The switching method according to claim 1, characterized in that, Each of the grid-type converters is a virtual synchronous machine, and the grid-connected simulation parameters of each virtual synchronous machine may be the same or different.

5. The switching method according to claim 1, characterized in that, The locations of each of the potential fault nodes are set on the AC system side.

6. The switching method according to claim 1, characterized in that, The simulation of each of the aforementioned faults yields the transient power angle versus time relationship for each grid-type converter under each fault, including: For each of the aforementioned faults, the electromagnetic transient conditions of each of the grid-type converters are simulated to obtain the transient power angle and time correspondence of each of the grid-type converters under each fault. The transient power angle is determined based on the active power loop output phase angle of the grid-type converter and the grid phase angle.

7. A converter operating mode switching device, characterized in that, include: The simulation system building unit is used to deploy grid-type converters at all new energy power nodes according to the actual power grid system topology, and build a simulation system composed of the deployed grid-type converters. The fault setting unit is used to set different faults at each possible fault node location in the simulation system to cause the grid voltage to drop. The simulation unit is used to simulate each of the aforementioned faults and obtain the transient power angle and time correspondence of each grid-type converter under each of the aforementioned faults. The determining unit is used to determine the comprehensive participation factor of each grid-type converter based on the transient power angle and time correspondence of each grid-type converter under different faults, wherein the value of the comprehensive participation factor is used to characterize the degree of disturbance of the grid-type converter under different faults. The switching unit is used to switch the node location of the target grid-type converter, where the comprehensive participation factor is less than a preset threshold, from the target grid-type converter to a grid-following converter. The determining unit includes: The participation factor determination subunit is used to determine the participation factor of each grid-type converter based on the transient power angle and time correspondence of each grid-type converter under a single fault, wherein the participation factor is used to characterize the degree of disturbance of the grid-type converter under a single fault. The comprehensive participation factor determination subunit is used to obtain the comprehensive participation factor of each grid-type converter based on the participation factor corresponding to each grid-type converter under different faults and the probability of different fault occurrences.

8. The switching device according to claim 7, characterized in that, The participation factor determination subunit is specifically used for: Based on the transient power angle and time correspondence of each grid-type converter under a single fault, the first rotor angle of the grid-type converter corresponding to the first moment of the transient process maturity period and the second rotor angle of the grid-type converter corresponding to the second moment are determined, wherein the first moment and the second moment are any two moments in the transient process maturity period. Calculate the rotor angle difference between the second rotor angle and the first rotor angle of the grid converter corresponding to each of the grid converters; The participation factor of the target grid-type converter with the highest rotor angle difference value is set to 1; The participation factor of each of the network converters other than the target network converter is determined based on the target rotor angle difference corresponding to the target network converter.

9. The switching device according to claim 8, characterized in that, The participation factor determination subunit is further used for: Calculate the quotient of the rotor angle difference of each of the grid-type converters other than the target grid-type converter with respect to the target rotor angle difference, and determine the quotient as the participation factor of the corresponding grid-type converter.

10. The switching device according to claim 7, characterized in that, The simulation unit is specifically used for: For each of the aforementioned faults, the electromagnetic transient conditions of each of the grid-type converters are simulated to obtain the transient power angle and time correspondence of each of the grid-type converters under each fault. The transient power angle is determined based on the active power loop output phase angle of the grid-type converter and the grid phase angle.

Images