Active support type flexible direct current converter alternating current side fault transient / steady state calculation method and active support type flexible direct current converter alternating current side fault transient / steady state calculation system

Abstract

The invention discloses an active support type flexible DC converter AC side fault transient / steady state calculation method and system, and the method comprises the steps: constructing a flexible DC converter control response equation and an AC side power grid constraint equation, and carrying out the simultaneous solving of a time domain fault transient / steady state current and a grid-connected point voltage outputted by a flexible DC converter; according to the time-domain fault transient / steady state current output by the flexible direct current converter and a current amplitude limiting value of a flexible direct current converter control system, judging whether the current output by the flexible direct current converter is out of limit or not; obtaining an alternating current fault transient / steady state calculation result under a corresponding condition; and outputting an AC fault transient / steady state calculation result. According to the invention, a basis is provided for fault analysis and protection configuration of the new energy access AC system.

Description

Technical Field

[0001] This invention relates to novel power system fault analysis and relay protection, specifically to a method for calculating transient / steady-state faults on the AC side of an actively supported flexible DC converter. Background Technology

[0002] With the increasing replacement of synchronous generators by inverter-type power supplies, active support control is required for flexible DC systems. These systems must provide voltage and frequency support to the grid while simultaneously delivering power, showing broad application prospects in scenarios such as islanded operation of new energy systems and support for weak grids. To enhance grid support capabilities, actively supported converters possess higher overcurrent tolerance and incorporate step-down control in fault ride-through control to maximize the controllability of the AC-side output voltage. Therefore, when a fault occurs in the AC-side grid, the voltage-current control loop in the actively supported converter will result in a different fault output compared to traditional grid-connected converters. The coupling effect between the voltage and current control loops increases, leading to higher expression orders and nonlinearities, resulting in complex transient and steady-state electrical characteristics on the AC side after a fault, significantly increasing the difficulty of fault analysis. Consequently, the output characteristics of actively supported flexible DC converters after AC-side faults are influenced by grid-connected control strategies, rendering traditional fault transient / steady-state calculation methods based on the power outer loop and current inner loop inapplicable. Furthermore, the saturation of the voltage controller during the control response process also needs to be considered, further increasing the complexity of fault analysis. In existing engineering projects, most methods for obtaining the transient and steady-state electrical characteristics of actively supported converters after AC-side faults rely on numerical simulations. However, the results are limited by the specific system topology and parameters. There is an urgent need to research transient / steady-state calculation methods for actively supported converters to provide a basis for fault analysis and protection configuration in AC systems with renewable energy integration. Summary of the Invention

[0003] To effectively address the problems in the background technology, this invention proposes a method and system for calculating the transient / steady-state faults on the AC side of an actively supported flexible DC converter. This method considers the control responses of the voltage controller and current controller to achieve transient / steady-state calculations for AC side faults, specifically addressing typical scenarios of short-circuit faults in AC lines.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] In a first aspect, this invention proposes a method for calculating transient / steady-state faults on the AC side of an actively supported flexible DC converter, comprising:

[0006] S1. Construct the control response equation of the flexible DC converter and the constraint equation of the AC side power grid, and solve them simultaneously to find the time-domain fault transient / steady-state current and its grid connection point voltage output by the flexible DC converter.

[0007] S2. Based on the time-domain fault transient / steady-state current output by the flexible DC converter and the current limit value of the flexible DC converter control system, determine whether the current output by the flexible DC converter has exceeded the limit: if no limit has been exceeded, use the time-domain fault transient / steady-state current output by the flexible DC converter and the grid connection point voltage as the first AC fault transient / steady-state calculation result; if a limit has been exceeded, use the current limit value as the current reference value of the flexible DC converter control system, and then solve for the second AC side fault transient / steady-state calculation result.

[0008] S3. Output the transient / steady-state calculation results of the first AC side fault and the transient / steady-state calculation results of the second AC side fault.

[0009] In some implementations, the construction of the flexible DC converter control response equation and the AC-side grid constraint equation, and the simultaneous solution of the time-domain transient / steady-state current output by the flexible DC converter, further includes constructing a set of differential equations by combining the flexible DC converter control response equation and the AC-side grid constraint equation, and using the set of differential equations to solve the time-domain fault transient / steady-state current output by the flexible DC converter.

[0010] In some embodiments, the flexible DC-DC converter control response equation further includes a flexible DC-DC converter voltage control response equation and a flexible DC-DC converter current control response equation.

[0011] The voltage control response equation for the flexible DC converter is shown below:

[0012] ;

[0013] in, , These represent the current reference values ​​at fault response time t, where t represents the fault response time. , These represent the voltage reference values ​​at fault response time t, , These represent the grid connection point voltages of the actively supported flexible DC converter at fault response time t. , Let k represent the output current of the actively supported flexible DC converter at fault response time t. p.o k represents the proportional coefficient of the voltage controller. i.o This represents the integral coefficient of the voltage controller;

[0014] Furthermore, the current control response equation for the flexible DC converter is shown below:

[0015] ;

[0016] in, , The grid connection point voltage of the active-supported flexible DC converter at fault response time t. , k represents the output current of the actively supported flexible DC converter at fault response time t. p.i k represents the proportional coefficient of the current controller. i.i This represents the integral coefficient of the current controller. , R represents the reference current value at fault response time t. c L c This indicates the AC side resistance and inductance of an actively supported flexible DC converter;

[0017] The AC-side power grid constraint equations are as follows:

[0018] ;

[0019] Among them, U s This represents the voltage amplitude of the synchronous generator, and δ represents the power angle of the power sources on both sides. , These represent the grid connection point voltages of the actively supported flexible DC converter at fault response time t. , These represent the output current of the active-supported flexible DC converter at fault response time t, respectively. , R represents the synchronous generator output current at fault response time t. r L r R represents the resistance and inductance from the synchronous generator outlet to the fault point. g R represents the transition resistance. s L s This represents the resistance and inductance from the outlet of the actively supported flexible DC converter to the fault point, ω. * This indicates the rated frequency of the AC system.

[0020] In some implementations, the calculated converter output current is determined based on the current limit value. If it exceeds the limit, the current limit value is substituted into the current control response equation of the flexible DC converter to calculate the output current of the flexible DC converter. Then, it is substituted into the AC side grid constraint equation to recalculate the grid connection point voltage of the flexible DC converter and the output current of the synchronous generator. The recalculated grid connection point voltage of the flexible DC converter and the output current of the synchronous generator are used as the second AC fault transient steady-state calculation result.

[0021] Secondly, an active-supported flexible DC converter AC side fault transient / steady-state calculation system includes:

[0022] The converter and AC system parameter acquisition module is used to construct the control response equation of the flexible DC converter and the AC side grid constraint equation, and simultaneously solve the time-domain fault transient and steady-state current and its grid connection point voltage output by the flexible DC converter.

[0023] The AC fault transient / steady-state signal calculation module is used to determine whether the current output by the flexible DC converter has exceeded the limit based on the time-domain fault transient / steady-state current output by the flexible DC converter and the current limit value of the flexible DC converter control system. If no limit has been exceeded, the time-domain fault transient / steady-state current output by the flexible DC converter and the grid connection point voltage are used as the first AC fault transient / steady-state calculation result. If a limit has been exceeded, the current limit value is used as the current reference value of the flexible DC converter control system, and then the second AC side fault transient / steady-state calculation result is obtained.

[0024] An AC fault transient / steady-state signal output module is used to output the transient / steady-state calculation results of the first AC side fault and the transient / steady-state calculation results of the second AC side fault.

[0025] In some implementations, the construction of the control response equations of the actively supported flexible DC converter and the AC-side grid constraint equations, and the simultaneous solution of the time-domain transient / steady-state current output by the flexible DC converter, further includes constructing a set of differential equations by combining the control response equations of the flexible DC converter and the AC-side grid constraint equations, and using the set of differential equations to solve the time-domain fault transient / steady-state current output by the flexible DC converter.

[0026] In some embodiments, the flexible DC-DC converter control response equation further includes a flexible DC-DC converter voltage control response equation and a flexible DC-DC converter current control response equation:

[0027] The voltage control response equation for the flexible DC converter is shown below:

[0028] ;

[0029] in, , These represent the current reference values ​​at fault response time t, where t represents the fault response time. , These represent the voltage reference values ​​at fault response time t, , These represent the grid connection point voltages of the actively supported flexible DC converter at fault response time t. , Let k represent the output current of the actively supported flexible DC converter at fault response time t. p.o k represents the proportional coefficient of the voltage controller. i.oThis represents the integral coefficient of the voltage controller;

[0030] Furthermore, the current control response equation for the flexible DC converter is shown below:

[0031] ;

[0032] in, , The grid connection point voltage of the active-supported flexible DC converter at fault response time t. , k represents the output current of the actively supported flexible DC converter at fault response time t. p.i k represents the proportional coefficient of the current controller. i.i This represents the integral coefficient of the current controller. , R represents the reference current value at fault response time t. c L c This indicates the AC side resistance and inductance of an actively supported flexible DC converter;

[0033] The AC-side power grid constraint equations are as follows:

[0034] ;

[0035] Among them, U s This represents the voltage amplitude of the synchronous generator, and δ represents the power angle of the power sources on both sides. , These represent the grid connection point voltages of the actively supported flexible DC converter at fault response time t. , These represent the output current of the active-supported flexible DC converter at fault response time t, respectively. , R represents the synchronous generator output current at fault response time t. r L r R represents the resistance and inductance from the synchronous generator outlet to the fault point. g R represents the transition resistance. s L s This represents the resistance and inductance from the outlet of the actively supported flexible DC converter to the fault point, ω. * This indicates the rated frequency of the AC system.

[0036] In some implementations, the calculated converter output current is determined based on the current limit value. If it exceeds the limit, the current limit value is substituted into the current control response equation of the flexible DC converter to calculate the output current of the flexible DC converter. Then, it is substituted into the AC side grid constraint equation to recalculate the grid connection point voltage of the flexible DC converter and the output current of the synchronous generator. The recalculated grid connection point voltage of the flexible DC converter and the output current of the synchronous generator are used as the second AC fault transient steady-state calculation result.

[0037] Thirdly, the present invention proposes an electronic device comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements a method for calculating transient / steady-state faults on the AC side of an actively supported flexible DC converter.

[0038] Fourthly, the present invention proposes a non-transitory computer-readable storage medium storing a computer program, which, when executed by a processor, implements a method for calculating transient / steady-state faults on the AC side of an actively supported flexible DC converter.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] 1) A current limit value was designed as a constraint to calculate AC fault transient / steady-state signals. If the constraint is met, the output current and grid connection point voltage of the actively supported flexible DC converter are calculated using the voltage controller response, current controller response, and grid topology constraints as the AC fault transient / steady-state calculation results. If the constraint is not met, the output current and grid connection point voltage of the flexible DC converter are calculated using the current controller response and grid topology constraints as the AC fault transient / steady-state calculation results. Considering the influence of the voltage controller on the AC side output of the grid-connected actively supported flexible DC converter, this invention provides a basis for AC system fault analysis and relay protection configuration for new energy access.

[0041] 2) In response to a short-circuit fault on the AC side, construct the control response equation of the active-supported flexible DC converter and the AC side grid constraint equation, and solve the time-domain fault transient / steady-state current output by the flexible DC converter as an important criterion for obtaining AC fault transient / steady-state calculation. Attached Figure Description

[0042] Figure 1 This is a flowchart of the AC-side fault transient / steady-state calculation method for the active-supported flexible DC converter of the present invention.

[0043] Figure 2 This is a roadmap for the AC-side fault transient / steady-state calculation technology of the active-supported flexible DC converter of the present invention.

[0044] Figure 3 This is a topology diagram of an AC power grid connected to an actively supported flexible DC converter.

[0045] Figure 4 This is a logic diagram of the grid control strategy for an actively supported flexible DC converter.

[0046] Figure 5 This is a block diagram of the AC-side fault transient / steady-state calculation system for the active-supported flexible DC converter of the present invention. Detailed Implementation

[0047] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings. The accompanying drawings of the embodiments of the present invention provide a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0048] Example 1: Combining with, for example Figure 1 As shown, the present invention provides a method for calculating transient / steady-state faults on the AC side of an actively supported flexible DC converter, and, as... Figure 2 The diagram shown is a technical roadmap for AC-side fault transient / steady-state calculation of the actively supported flexible DC converter of the present invention. The specific process of this method includes the following steps:

[0049] Step 1: Construct the control response equations of the flexible DC converter and the AC-side grid constraint equations, and simultaneously solve for the time-domain fault transient / steady-state current output of the flexible DC converter and its grid connection point voltage; the specific description is as follows:

[0050] like Figure 3 The diagram shows a two-terminal AC system. Taking this two-terminal AC system as an example, the M and N sides represent an actively supported flexible DC converter and a synchronous generator, respectively. Figure 4 As shown, the actively supported flexible DC converter adopts a grid-based control strategy, including a power controller, a voltage controller, and a current controller. The operating and fault ride-through control parameters of the actively supported flexible DC converter are obtained, all expressed as dq components, including the voltage controller proportional coefficient k. p.o Integral coefficient k i.o dq voltage limiting value u d * u q * ; proportional coefficient k of the current controller p.i Integral coefficient k of current controller i.i AC side resistance R of actively supported flexible DC converter c Inductor L c dq current limiting value i d * i q* ;

[0051] Step 1.1: Obtain AC side system parameters, including synchronous generator voltage amplitude U. s The power angle δ of the power supplies on both sides, and the rated frequency ω of the AC system. * The resistance R from the synchronous generator outlet to the fault point r Inductor L r The resistance R from the outlet of the actively supported flexible DC converter to the fault point s Inductor L s and transition resistance R g .

[0052] The output current i of the actively supported flexible DC converter is calculated based on the parameters of the active-supported flexible DC converter and the AC side system parameters. d i q Synchronous generator output current i r.d i r.q The AC-side grid connection point voltage u of the actively supported flexible DC converter d u q ; Including the output current i of the actively supported flexible DC converter d i q Synchronous generator output current i r.d i r.q The AC-side grid connection point voltage u of the actively supported flexible DC converter d u q .

[0053] The control response equations of the flexible DC converter and the constraint equations of the AC-side grid are constructed, and the time-domain transient and steady-state currents output by the flexible DC converter are solved and analyzed. The solution results also include the grid connection point voltage and the time-domain transient and steady-state currents output by the AC-side system. Figure 3 For example, the specific description is as follows:

[0054] Step 1.2: After a fault occurs on the AC side, the power controller based on voltage amplitude and frequency quickly reaches its limiting value, i.e., saturation. The voltage limiting value u is then adjusted. d * u q * and current limiting value dq component i d * i q * The voltage limit value u is transmitted to the voltage controller as the voltage reference value and the current reference value, respectively. d * u q * The fault ride-through control provides a fixed frequency of the AC grid's rated frequency, and the voltage controller output current limit value i.d * i q * Based on the working principle of the voltage controller, the voltage control response equation of the flexible DC converter is constructed as follows:

[0055] ;

[0056] in, , These represent the current reference values ​​at fault response time t, where t represents the fault response time. , These represent the voltage reference values ​​at fault response time t, , These represent the grid connection point voltages of the actively supported flexible DC converter at fault response time t. , Let k represent the output current of the actively supported flexible DC converter at fault response time t. p.o k represents the proportional coefficient of the voltage controller. i.o This represents the integral coefficient of the voltage controller;

[0057] When the voltage controller outputs the dq current reference value , When the current limit is not reached, the dq current reference value transmitted to the current controller is provided by the voltage controller; while when the voltage controller outputs the dq current reference value... , When the current limit is reached, the reference value of the dq current transmitted to the current controller becomes the current limit. Based on the working principle of the current controller and the AC side topology of the actively supported flexible DC converter, the current control response equation of the flexible DC converter is constructed as follows:

[0058] ;

[0059] in, , The grid connection point voltage of the active-supported flexible DC converter at fault response time t. , k represents the output current of the actively supported flexible DC converter at fault response time t. p.i k represents the proportional coefficient of the current controller. i.i This represents the integral coefficient of the current controller. , R represents the reference current value at fault response time t. c L c This indicates the AC side resistance and inductance of an actively supported flexible DC converter;

[0060] Step 1.3: Construct the AC side power grid constraint equations:

[0061] Based on the topology between the actively supported flexible DC converter, synchronous generator, and fault point, the constraint equations for the AC-side power grid are constructed as follows:

[0062] ;

[0063] Among them, U s This represents the voltage amplitude of the synchronous generator, and δ represents the power angle of the power sources on both sides. , These represent the grid connection point voltages of the actively supported flexible DC converter at fault response time t. , These represent the output current of the active-supported flexible DC converter at fault response time t, respectively. , R represents the synchronous generator output current at fault response time t. r L r R represents the resistance and inductance from the synchronous generator outlet to the fault point. g R represents the transition resistance. s L s This represents the resistance and inductance from the outlet of the actively supported flexible DC converter to the fault point, ω. * Indicates the rated frequency of the AC system;

[0064] Step 1.4: Based on the control response equation of the active-supported flexible DC converter and the constraint equation of the AC-side power grid, construct a set of differential equations and solve them to obtain the current limit value, as described in detail below;

[0065] The control response equations of the actively supported flexible DC converter and the AC-side grid constraint equations are combined, wherein:

[0066] The variables include: , , , , , , , , ,

[0067] The corresponding variable derivative: , , , , , , , , ,

[0068] Construct a system of differential equations:

[0069] The currents d and q, along with their integrals, are simultaneously treated as variables in the system of differential equations. When calculating the time-domain transient numerical solution of each variable, the expression of the system of differential equations is considered:

[0070] , ;

[0071] Calculate the time-domain transient numerical solutions for each variable, including the time-domain transient and steady-state currents and grid connection point voltages output by the flexible DC converter, as well as the time-domain transient and steady-state currents output by the AC side system.

[0072] Step 2: Based on the time-domain fault transient / steady-state current output by the flexible DC converter and the current limit value of the converter control system, determine whether the current output by the flexible DC converter has exceeded the limit: If no limit has been exceeded, use the time-domain fault transient / steady-state current output by the flexible DC converter and the grid connection point voltage as the first AC fault transient / steady-state calculation result; if a limit has been exceeded, use the current limit value as the current reference value of the flexible DC converter control system, and then solve for the second AC side fault transient / steady-state calculation result, as described in detail below:

[0073] i. If the output current i of the actively supported flexible DC converter calculated in step 1 is... d i q If the dq current limit is not reached, it is determined that the current of the actively supported flexible DC converter has not exceeded the limit. At this time, the voltage controller has not reached saturation, and the output current i of the actively supported flexible DC converter is... d i q The final AC fault transient / steady-state calculation results, specifically including dq transient / steady-state voltage and dq transient / steady-state current, are then used to proceed to step 5.

[0074] ii. If the actively supported flexible DC converter calculated in step 1 is i d i q If the dq current limit is reached, it is determined that the current of the actively supported flexible DC converter has exceeded the limit. At this time, the voltage controller reaches saturation. The dq current limit is directly substituted into the current control response equation in step 2 to calculate the output current i of the actively supported flexible DC converter. d i q Then, substituting the AC-side grid constraint equations from step 2, the grid connection point voltage u of the flexible DC converter is calculated. d u q and synchronous generator output current i r.d ir.q As the final result of the second AC fault transient / steady-state calculation, specifically including dq transient / steady-state voltage and dq transient / steady-state current, proceed to step 3.

[0075] Step 3: Output the AC fault transient / steady-state calculation results, as detailed below:

[0076] After an AC-side fault, the real-time phase angle frequency in the active-support flexible DC converter control system is fixed at the rated frequency of the AC power grid. Therefore, based on the rated frequency, an inverse dq transformation is performed on the calculation results in step 4, including: the flexible DC converter output current i d i q Synchronous generator output current i r.d i r.q The voltage u at the AC side grid connection point of the flexible DC converter d u q Output the final fault transient / steady-state calculation results.

[0077] Example 2, as follows Figure 5 The diagram shown is a block diagram of the AC-side fault transient / steady-state calculation system for the actively supported flexible DC converter of the present invention. The system includes a converter and AC system parameter acquisition module 100, an AC fault transient / steady-state signal calculation module 200, and an AC fault transient / steady-state signal output module 300.

[0078] The converter and AC system parameter acquisition module 100 is used to construct the control response equation of the flexible DC converter and the constraint equation of the AC side power grid, and simultaneously solve the time-domain fault transient and steady-state current output by the flexible DC converter.

[0079] The AC fault transient / steady-state signal calculation module 200 is used to determine whether the current output by the flexible DC converter has exceeded the limit based on the time-domain fault transient / steady-state current output by the flexible DC converter and the current limit value of the flexible DC converter control system. If no limit has been exceeded, the time-domain fault transient / steady-state current output by the flexible DC converter and the grid connection point voltage are used as the AC fault transient / steady-state calculation result one. If a limit has been exceeded, the current limit value is used as the AC side output current of the flexible DC converter, and the AC side fault transient / steady-state calculation result two is calculated.

[0080] The AC fault transient / steady-state signal output module 300 is used to output AC fault transient / steady-state calculation results, including AC fault transient / steady-state calculation result one and AC fault transient / steady-state calculation result two, which are output based on whether the current exceeds the limit.

[0081] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of the present invention can be implemented using various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0082] Example 3: A non-transitory computer-readable storage medium storing a computer program that, when executed by a processor, implements a transient / steady-state calculation method for AC-side faults in an actively supported flexible DC-DC converter according to Example 1 of the present invention. The present invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It should be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate methods for implementing the transient / steady-state calculation method for AC-side faults in an actively supported flexible DC-DC converter. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0083] Example 4: An electronic device comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements a transient / steady-state calculation method for AC-side faults of an actively supported flexible DC-DC converter according to Example 1 of the present invention. These computer program instructions may also be stored in a computer-readable storage medium capable of directing a computer or other programmable data processing device to operate in a specific manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process... Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0084] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0085] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention.

[0086] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for calculating transient / steady-state faults on the AC side of an actively supported flexible DC converter, characterized in that, include: Construct the control response equations of the flexible DC converter and the AC grid constraint equations, and solve them simultaneously to find the time-domain fault transient / steady-state current and its grid connection point voltage at the output of the flexible DC converter. Based on the time-domain fault transient / steady-state current output by the flexible DC converter and the current limit value of the flexible DC converter control system, it is determined whether the current output by the flexible DC converter exceeds the limit: if no limit is exceeded, the time-domain fault transient / steady-state current output by the flexible DC converter and the grid connection point voltage are used as the first AC fault transient / steady-state calculation result. If the limit has been exceeded, the current limit value is used as the current reference value of the flexible DC converter control system, and then the transient / steady-state calculation results of the second AC side fault are solved. Output the transient / steady-state calculation results of the first AC side fault and the transient / steady-state calculation results of the second AC side fault.

2. The method for calculating transient / steady-state faults on the AC side of an actively supported flexible DC converter according to claim 1, characterized in that, The construction of the flexible DC converter control response equation and the AC-side grid constraint equation, and the simultaneous solution of the time-domain transient / steady-state current output by the flexible DC converter, further includes: constructing a set of differential equations by combining the flexible DC converter control response equation and the AC-side grid constraint equation, and using the set of differential equations to solve the time-domain fault transient / steady-state current output by the flexible DC converter.

3. The method for calculating transient / steady-state faults on the AC side of an actively supported flexible DC converter according to claim 1, characterized in that, The flexible DC-DC converter control response equation further includes a flexible DC-DC converter voltage control response equation and a flexible DC-DC converter current control response equation. The voltage control response equation for the flexible DC converter is shown below: ; in, , These represent the current reference values ​​at fault response time t, where t represents the fault response time. , These represent the voltage reference values ​​at fault response time t, , These represent the grid connection point voltages of the actively supported flexible DC converter at fault response time t. , Let k represent the output current of the actively supported flexible DC converter at fault response time t. p.o k represents the proportional coefficient of the voltage controller. i.o This represents the integral coefficient of the voltage controller; Furthermore, the current control response equation for the flexible DC converter is shown below: ; in, , The grid connection point voltage of the active-supported flexible DC converter at fault response time t. , k represents the output current of the actively supported flexible DC converter at fault response time t. p.i k represents the proportional coefficient of the current controller. i.i This represents the integral coefficient of the current controller. , R represents the reference current value at fault response time t. c L c This indicates the AC side resistance and inductance of an actively supported flexible DC converter; The AC-side power grid constraint equations are as follows: ; Among them, U s This represents the voltage amplitude of the synchronous generator, and δ represents the power angle of the power sources on both sides. , These represent the grid connection point voltages of the actively supported flexible DC converter at fault response time t. , These represent the output current of the active-supported flexible DC converter at fault response time t, respectively. , R represents the synchronous generator output current at fault response time t. r L r R represents the resistance and inductance from the synchronous generator outlet to the fault point. g R represents the transition resistance. s L s Indicates the outlet of the actively supported flexible DC converter to The resistance and inductance at the fault point, ω * This indicates the rated frequency of the AC system.

4. The method for calculating transient / steady-state faults on the AC side of an actively supported flexible DC converter according to claim 3, characterized in that, The current limit value is used to determine whether the calculated converter output current exceeds the limit. If it does, the current limit value is substituted into the current control response equation of the flexible DC converter to calculate the output current of the flexible DC converter. Then, it is substituted into the AC side grid constraint equation to recalculate the grid connection point voltage of the flexible DC converter and the output current of the synchronous generator. The recalculated grid connection point voltage of the flexible DC converter and the output current of the synchronous generator are used as the second AC fault transient steady state calculation result.

5. A fault transient / steady-state calculation system for an actively supported flexible DC converter on the AC side, characterized in that, include: The converter and AC system parameter acquisition module is used to construct the control response equation of the flexible DC converter and the AC side grid constraint equation, and simultaneously solve the time-domain fault transient and steady-state current and its grid connection point voltage output by the flexible DC converter. The AC fault transient / steady-state signal calculation module is used to determine whether the current output by the flexible DC converter has exceeded the limit based on the time-domain fault transient / steady-state current output by the flexible DC converter and the current limit value of the flexible DC converter control system. If no limit has been exceeded, the time-domain fault transient / steady-state current output by the flexible DC converter and the grid connection point voltage are used as the first AC fault transient / steady-state calculation result. If the limit has been exceeded, the current limit value is used as the current reference value of the flexible DC converter control system, and then the transient / steady-state calculation results of the second AC side fault are solved. An AC fault transient / steady-state signal output module is used to calculate the transient / steady-state result of a first AC-side fault or a second AC-side fault transient / steady-state result.

6. The active-supported flexible DC converter AC side fault transient / steady-state calculation system according to claim 1, characterized in that, The converter and AC system parameter acquisition module is also used to construct a set of differential equations by combining the control response equation of the flexible DC converter and the constraint equation of the AC grid, and to solve the time-domain fault transient / steady-state current output by the flexible DC converter using the set of differential equations.

7. The active-supported flexible DC converter AC side fault transient / steady-state calculation system according to claim 1, characterized in that, The flexible DC-DC converter control response equation further includes a flexible DC-DC converter voltage control response equation and a flexible DC-DC converter current control response equation. The voltage control response equation for the flexible DC converter is shown below: ; in, , These represent the current reference values ​​at fault response time t, where t represents the fault response time. , These represent the voltage reference values ​​at fault response time t, , These represent the grid connection point voltages of the actively supported flexible DC converter at fault response time t. , Let k represent the output current of the actively supported flexible DC converter at fault response time t. p.o k represents the proportional coefficient of the voltage controller. i.o This represents the integral coefficient of the voltage controller; Furthermore, the current control response equation for the flexible DC converter is shown below: ; in, , The grid connection point voltage of the active-supported flexible DC converter at fault response time t. , k represents the output current of the actively supported flexible DC converter at fault response time t. p.i k represents the proportional coefficient of the current controller. i.i This represents the integral coefficient of the current controller. , R represents the reference current value at fault response time t. c L c This indicates the AC side resistance and inductance of an actively supported flexible DC converter; The AC-side power grid constraint equations are as follows: ; Among them, U s This represents the voltage amplitude of the synchronous generator, and δ represents the power angle of the power sources on both sides. , These represent the grid connection point voltages of the actively supported flexible DC converter at fault response time t. , These represent the output current of the active-supported flexible DC converter at fault response time t, respectively. , R represents the synchronous generator output current at fault response time t. r L r R represents the resistance and inductance from the synchronous generator outlet to the fault point. g R represents the transition resistance. s L s This represents the resistance and inductance from the outlet of the actively supported flexible DC converter to the fault point, ω. * This indicates the rated frequency of the AC system.

8. The active-supported flexible DC converter AC side fault transient / steady-state calculation system according to claim 7, characterized in that, The AC fault transient / steady-state signal calculation module is also used to determine whether the calculated converter output current exceeds the limit based on the current limit value. If it does, the current limit value is substituted into the flexible DC converter current control response equation to calculate the flexible DC converter output current. Then, it is substituted into the AC side grid constraint equation to recalculate the flexible DC converter grid connection point voltage and the synchronous generator output current. The recalculated flexible DC converter grid connection point voltage and synchronous generator output current are used as the second AC fault transient / steady-state calculation result.

9. An electronic device, comprising: The system includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements a method for calculating transient / steady-state faults on the AC side of an actively supported flexible DC converter according to any one of claims 1 to 4.

10. A non-transitory computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements a transient / steady-state calculation method for AC-side faults of an actively supported flexible DC converter according to any one of claims 1 to 4.

Images