A negative sequence voltage control method and system for a grid-connected converter

Abstract

The present disclosure provides a negative-sequence voltage control method and system for a grid-type converter, which relates to the technical field of grid-type converter control, including: calculating the negative-sequence reactive power absorbed by the converter and the maximum negative-sequence reactive power that can be absorbed under a specified fault condition based on the rated phase voltage of the converter, the grid voltage amplitude, and the converter voltage amplitude, and comparing the two to obtain a negative-sequence active power instruction and a negative-sequence reactive power instruction; performing droop control using the negative-sequence active power instruction; performing PI control using the negative-sequence reactive power instruction; when a fault occurs, performing three-phase voltage and current sequence decomposition to obtain the converter negative-sequence voltage amplitude and phase and the negative-sequence current amplitude and phase; performing power measurement based on the converter output negative-sequence voltage amplitude and phase and the negative-sequence current amplitude and phase to obtain the negative-sequence active power and reactive power transmitted between the converter and the grid.

Description

Technical Field

[0001] The present disclosure relates to the technical field of grid-type converter control, and in particular to a negative-sequence voltage control method and system for a grid-type converter. Background Art

[0002] The statements in this section merely provide background information related to the present disclosure and do not necessarily constitute prior art.

[0003] Grid-forming control is a control strategy for power electronic converters. Its core goal is to enable the converter to autonomously establish and maintain system voltage and frequency without relying on an external grid or synchronization signals. This control method gives the converter "gridding" capabilities similar to traditional synchronous generators. Compared to traditional grid-following control methods, grid-forming converters provide inertial and damping support to the grid, offering enhanced voltage regulation capabilities in the event of grid faults. They are particularly well-suited for microgrids, islanded operation, and power systems with a high penetration of renewable energy.

[0004] When an asymmetric low-voltage fault occurs in the power grid (such as a single-phase ground fault), the grid voltage will generate a negative-sequence component. If this negative-sequence component is not controlled, there will be an overcurrent risk. According to the requirements of the national standard GB / T 34120-2023 "Technical Requirements for Energy Storage Converters of Electrochemical Energy Storage Systems", during an asymmetric low-voltage fault, the converter should have the ability to support the grid reactive power, that is, absorb the reactive power generated by the negative-sequence component of the grid voltage to avoid an increase in negative-sequence voltage.

[0005] Among existing methods for controlling negative-sequence voltage, negative-sequence current injection closed-loop control is the most mainstream approach. This approach suppresses negative-sequence voltage and current by introducing a negative-sequence synchronous rotating coordinate system into the converter's control loop to control the negative-sequence current component. However, this approach cannot achieve reactive and active power support for the grid during asymmetric faults. Specific harmonic elimination methods employ a proportional resonant (PR) controller or a dual-second-order generalized integrator (DSOGI) and its derivatives, specifically designed for the negative-sequence fundamental frequency, in an αβ stationary coordinate system. This approach incorporates high-gain control of the negative-sequence component into the voltage or current loop to achieve zero-error tracking or suppression of the negative-sequence component. However, the controller's time delay can cause negative-sequence current overshoot during asymmetric faults. Virtual negative-sequence impedance control methods stabilize negative-sequence power by actively setting a desired negative-sequence output impedance within the converter's equivalent output impedance model. While this approach suppresses negative-sequence components, it can reduce the converter's active power support capability. Summary of the Invention

[0006] In order to solve the above problems, the present disclosure proposes a negative-sequence voltage control method and system for a grid-type converter. By analyzing the limit values ​​of active power and reactive power that prevent transient instability of the negative-sequence voltage and power angle, the active power and reactive power are adjusted without causing negative-sequence instability, thereby improving the stability of grid operation.

[0007] According to some embodiments, the present disclosure adopts the following technical solutions:

[0008] A negative sequence voltage control method for a grid-type converter, comprising:

[0009] Constructing a topological structure for connecting the grid-connected converter to the power grid;

[0010] Obtain the rated phase voltage of the grid-connected converter, the grid voltage amplitude, and the voltage amplitude of the grid-connected converter. Based on the rated phase voltage of the converter, the grid voltage amplitude, and the converter voltage amplitude, calculate the negative-sequence reactive power absorbed by the converter and the maximum negative-sequence reactive power that can be absorbed under the specified fault condition, compare the two, and output a negative-sequence active power command and a negative-sequence reactive power command.

[0011] The negative-sequence active power command is used for droop control, and the phase angle of the converter output negative-sequence voltage is adjusted by changing the input negative-sequence active power command. The negative-sequence reactive power command is used for PI control, and the amplitude of the converter output negative-sequence voltage is adjusted by changing the input negative-sequence reactive power command. The phase angle and amplitude of the negative-sequence voltage are then modulated by PWM to generate the three-phase switching signal of the grid-type converter.

[0012] When a fault occurs, the three-phase voltage and current signals on the grid side are decomposed into three-phase voltage and current sequence to obtain the amplitude and phase of the negative sequence voltage, the amplitude and phase of the negative sequence current of the converter;

[0013] Power measurement is performed based on the amplitude and phase of the negative-sequence voltage, the amplitude of the negative-sequence current, and the phase of the negative-sequence current output by the converter to obtain the negative-sequence active power and reactive power transmitted between the converter and the grid, thereby completing the negative-sequence power control of the converter.

[0014] According to some embodiments, the present disclosure adopts the following technical solutions:

[0015] A negative sequence voltage control system for a grid-type converter, comprising:

[0016] Grid connection initialization module, used to build the topology structure of grid-connected converter and grid;

[0017] The negative-sequence power calculation and comparison module is used to obtain the rated phase voltage of the grid-connected converter, the grid voltage amplitude, and the voltage amplitude of the grid-connected converter. Based on the rated phase voltage of the converter, the grid voltage amplitude, and the converter voltage amplitude, it calculates the negative-sequence reactive power absorbed by the converter and the maximum negative-sequence reactive power that can be absorbed under the specified fault condition, compares the two, and outputs the negative-sequence active power command and the negative-sequence reactive power command;

[0018] The active power control module and the negative-sequence reactive power control module are used to perform droop control using the negative-sequence active power command, adjusting the phase angle of the converter output negative-sequence voltage by changing the input negative-sequence active power command; perform PI control using the negative-sequence reactive power command, adjusting the amplitude of the converter output negative-sequence voltage by changing the input negative-sequence reactive power command; and then generate the three-phase switching signal of the grid-type converter by PWM modulation of the phase angle and amplitude of the negative-sequence voltage;

[0019] The three-phase voltage and current sequence decomposition module is used to perform three-phase voltage and current sequence decomposition on the grid-side three-phase voltage signal and three-phase current signal when a fault occurs, and obtain the amplitude and phase of the negative sequence voltage of the converter, the amplitude and phase of the negative sequence current;

[0020] The power measurement module is used to measure power based on the amplitude and phase of the negative-sequence voltage output by the converter, the amplitude of the negative-sequence current, and the phase of the negative-sequence current, to obtain the negative-sequence active power and reactive power transmitted between the converter and the power grid, and to complete the negative-sequence power control of the converter.

[0021] According to some embodiments, the present disclosure adopts the following technical solutions:

[0022] A computer program product includes a computer program, wherein when the computer program is executed by a processor, the computer program implements the negative sequence voltage control method of a grid-type converter.

[0023] According to some embodiments, the present disclosure adopts the following technical solutions:

[0024] A non-transitory computer-readable storage medium is used to store computer instructions. When the computer instructions are executed by a processor, a negative-sequence voltage control method of a grid-type converter is implemented.

[0025] According to some embodiments, the present disclosure adopts the following technical solutions:

[0026] An electronic device comprises: a processor, a memory, and a computer program; wherein the processor is connected to the memory, the computer program is stored in the memory, and when the electronic device is running, the processor executes the computer program stored in the memory to enable the electronic device to implement the negative sequence voltage control method of a grid-type converter.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention discloses a negative-sequence voltage control method for a grid-type converter. By analyzing the limit values ​​of active power and reactive power that prevent transient instability of the negative-sequence voltage and power angle, the active and reactive power are adjusted without causing negative-sequence instability. This method satisfies the set standard requirement for the converter to provide negative-sequence dynamic reactive support to the grid during a grid fault as much as possible, thereby improving the stability of grid operation.

[0029] The present invention discloses a negative-sequence voltage control method for a grid-type converter. The method calculates the negative-sequence reactive power absorbed by the converter in accordance with set requirements under a specified fault condition and the maximum negative-sequence reactive power that the converter can absorb under the fault condition, and compares the two to timely adjust the active power command and the reactive power command so that the power command does not exceed the limit and the negative-sequence voltage and power angle do not experience transient instability. The process considers a maximum absorption limit of the converter for negative-sequence reactive power, reasonably obtains the power command of the grid-type converter, maintains the stability of the negative-sequence transient voltage or power angle, and improves the support capability of the power grid operation.

[0030] The present invention discloses a negative-sequence voltage control method for a grid-type converter, which uses a negative-sequence active power instruction for droop control and a negative-sequence reactive power instruction for PI control. By reasonably configuring controller parameters, rapid and accurate support for the active power and reactive power of the grid can be achieved.

[0031] The present invention discloses a negative-sequence voltage control method for a grid-type converter, which performs three-phase voltage and current sequence decomposition on the grid-side three-phase voltage signal and the three-phase current signal, respectively, so as to accurately obtain the amplitude and phase of the voltage negative-sequence component and the current negative-sequence component required for power calculation and power control, thereby achieving better control effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings, which constitute a part of the present disclosure, are used to provide a further understanding of the present disclosure. The exemplary embodiments of the present disclosure and their descriptions are used to explain the present disclosure and do not constitute an improper limitation to the present disclosure.

[0033] Figure 1 This is a structural diagram of a negative-sequence voltage control system for a grid-type converter according to an embodiment of the present disclosure;

[0034] Figure 2This is a schematic structural diagram of a negative-sequence reactive power control module according to an embodiment of the present disclosure;

[0035] Figure 3 Schematic diagram of the structure of the negative-sequence active power control module according to an embodiment of the present disclosure;

[0036] Figure 4 Schematic diagram of the structure of the negative sequence power calculation and comparison module according to an embodiment of the present disclosure;

[0037] Figure 5 This is a schematic diagram of the structure of a three-phase voltage and current sequence decomposition module according to an embodiment of the present disclosure;

[0038] Figure 6 Schematic diagram of the structure of the negative-sequence active / reactive power measurement module according to an embodiment of the present disclosure;

[0039] Figure 7 This is a simulation result diagram of active power transmitted between the converter and the power grid when transient instability of negative sequence voltage and power angle occurs in an embodiment of the present disclosure;

[0040] Figure 8 This is a diagram showing simulation results of reactive power transmitted between the converter and the power grid when transient instability of negative sequence voltage and power angle occurs in an embodiment of the present disclosure;

[0041] Figure 9 This is a simulation result diagram of the amplitude of the negative sequence component of the converter voltage when transient instability of the negative sequence voltage and power angle occurs in an embodiment of the present disclosure;

[0042] Figure 10 This is a simulation result diagram of active power transmitted between the converter and the power grid when no negative sequence voltage and power angle transient instability occurs after the power command is adjusted according to an embodiment of the present disclosure;

[0043] Figure 11 This is a diagram showing simulation results of reactive power transmitted between the converter and the power grid when no transient instability of negative sequence voltage and power angle occurs after adjusting the power command according to an embodiment of the present disclosure;

[0044] Figure 12 This is a simulation result diagram of the amplitude of the negative-sequence component of the converter voltage when no negative-sequence voltage and power angle transient instability occurs after adjusting the power command according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0045] The present disclosure will be further described below with reference to the accompanying drawings and embodiments.

[0046] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present disclosure. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present disclosure belongs.

[0047] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present disclosure. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0048] Example 1

[0049] In one embodiment of the present disclosure, a negative-sequence voltage control method for a grid-type converter is provided, comprising:

[0050] Step 1: Construct a topological structure for connecting the grid-connected converter to the power grid;

[0051] Step 2: Obtain the rated phase voltage of the grid-connected converter, the grid voltage amplitude, and the voltage amplitude of the grid-connected converter. Based on the rated phase voltage of the converter, the grid voltage amplitude, and the converter voltage amplitude, calculate the negative-sequence reactive power absorbed by the converter and the maximum negative-sequence reactive power that can be absorbed under the specified fault condition, compare the two, and output the negative-sequence active power command and negative-sequence reactive power command.

[0052] Step 3: Use the negative-sequence active power command for droop control, and adjust the phase angle of the converter output negative-sequence voltage by changing the input negative-sequence active power command; use the negative-sequence reactive power command for PI control, and adjust the amplitude of the converter output negative-sequence voltage by changing the input negative-sequence reactive power command; then use PWM modulation to generate the three-phase switching signal of the grid-type converter.

[0053] Step 4: When a fault occurs, the three-phase voltage and current signals on the grid side are decomposed into three-phase voltage and current sequence to obtain the amplitude and phase of the negative sequence voltage, the amplitude and phase of the negative sequence current of the converter;

[0054] Step 5: Power measurement is performed based on the amplitude and phase of the negative-sequence voltage output by the converter, the amplitude of the negative-sequence current, and the phase of the negative-sequence current to obtain the negative-sequence active power and reactive power transmitted between the converter and the grid, thereby completing the negative-sequence power control of the converter.

[0055] As an embodiment, the present disclosure discloses a negative-sequence voltage control method for a grid-connected converter. This method analyzes the limit values ​​of the active power command and reactive power command that prevent transient instability of the negative-sequence voltage and power angle, adjusts the active and reactive power commands without causing negative-sequence instability, and, when a grid fault occurs, performs negative-sequence voltage control and reactive power support on the grid while ensuring transient stability of the converter's output voltage and power angle. The specific implementation process of the method is as follows:

[0056] Step 1: Construct a topological structure for connecting the grid-connected converter to the power grid;

[0057] Specifically, if Figure 1 As shown, the topological structure of the grid-connected converter and the grid includes the grid-connected converter and the grid. The grid-connected converter is connected to the grid via an LCL filter, and the grid connection point is the PCC. A control system is constructed based on the topological structure of the grid-connected converter and the grid. The control system consists of the grid-connected converter, the grid, a negative-sequence reactive power control module, a negative-sequence active power control module, a negative-sequence power calculation and comparison module, a three-phase voltage and current sequence decomposition module, and a negative-sequence active / reactive power measurement module.

[0058] Step 2: Obtain the rated phase voltage of the grid-connected converter, the grid voltage amplitude, and the grid-type converter voltage amplitude. Based on the rated phase voltage of the converter, the grid voltage amplitude, and the converter voltage amplitude, calculate the negative-sequence reactive power absorbed by the converter and the maximum negative-sequence reactive power that can be absorbed under the specified fault condition, and compare the two to output the negative-sequence active power command and the negative-sequence reactive power command, including: extracting the rated phase voltage of the grid-connected converter V rms , grid voltage amplitude V sn and the voltage amplitude of the grid-type converter V gn , calculate the negative sequence reactive power absorbed by the converter under the specified fault conditions that meets the set requirements q gn The converter has a certain limit to absorb negative sequence reactive power. Once the limit is exceeded, transient voltage instability will occur. Based on the negative sequence active power exchanged between the converter and the grid, p g and negative sequence reactive power q g The transmission model is used to calculate the maximum negative sequence reactive power that the converter can absorb under this fault condition. q g_min_n , and compare the negative sequence reactive power absorbed by the converter that meets the set requirements with the maximum negative sequence reactive power that can be absorbed, and further adjust to obtain the active power instruction p g_ref and reactive power command q g_ref , so that the power instruction will not exceed the limit.

[0059] Specifically, the requirements are as follows: the energy storage converter is required to have the ability to dynamically support the grid's reactive power when an asymmetric low-voltage fault occurs in the grid. It needs to absorb negative-sequence reactive current to suppress the increase in negative-sequence voltage, that is, it needs to absorb a certain amount of reactive power generated by the grid's negative-sequence component. The standard requires that the specific calculation process of the negative-sequence reactive power absorbed by the converter be as follows:

[0060] (1)

[0061] Among them, Δ I t-is the negative sequence dynamic reactive current increment absorbed by the converter; q gn is the negative sequence reactive power that the standard requires the converter to absorb; K 2 is the converter dynamic negative sequence reactive current proportional coefficient, which should be no less than 1.0; U t-is the per-unit value of the negative sequence component of the AC port voltage of the converter; I N is the rated current of the converter, V rms is the effective value of the rated phase voltage of the converter.

[0062] However, the converter has a certain limit on absorbing negative-sequence reactive power. Once the limit is exceeded, transient voltage instability will occur. The transmission model of negative-sequence active power and negative-sequence reactive power exchanged between the converter and the grid is expressed as follows:

[0063] (2)

[0064] in, V sn is the grid voltage amplitude, V gn is the converter voltage amplitude, δ g is the power angle, L gs is the inductance of the transmission line between the converter and the grid. The maximum negative sequence reactive power that the converter can absorb is expressed as follows according to equation (2):

[0065] (3)

[0066] in, X gs is the transmission impedance comparison of the transmission line between the converter and the grid q g_min_n and q gn, if q g_min_n≤ q gn, then let q g_ref= q gn, q g_ref is the input reference command value of the reactive power control module; if q g_min_n≥ q gn, you need to ensure q g_ref≥q g_min_n, otherwise negative sequence voltage transient instability will occur. In order to achieve the best reactive support effect, take q g_ref= q g_min_n. After determining q After g_ref (negative sequence reactive power command), the specific calculation formula for the maximum negative sequence active power transmitted between the converter and the grid is as follows:

[0067] (4)

[0068] The given active power control module input reference instruction p g_ref (negative sequence active power command) cannot be greater than p g_max_n, otherwise the negative sequence power angle transient instability will occur. Compare the negative sequence active power output of the converter required by the standard under the specified fault condition p gn and p g_max_n, if p g_max_n≥ p gn, take p g_ref= p gn; if p g_max_n≤ p gn, in order to achieve maximum active power transmission, take p g_ref= p g_max_n.

[0069] Step 3: Using the negative-sequence active power instruction to perform droop control, by changing the input negative-sequence active power instruction to adjust the phase angle of the negative-sequence voltage output by the converter; using the negative-sequence reactive power instruction to perform PI control, by changing the input negative-sequence reactive power instruction to adjust the amplitude of the negative-sequence voltage output by the converter; then the phase angle and amplitude of the negative-sequence voltage are modulated by PWM to generate a three-phase switching signal of the grid-forming converter, including: using the negative-sequence active power instruction to perform droop control, according to the active-frequency droop characteristic curve of the synchronous generator, by changing the input negative-sequence active power instruction to adjust the phase angle of the negative-sequence voltage output by the converter, thereby changing the negative-sequence active power transmitted between the converter and the grid. PI control is performed using the negative-sequence reactive power instruction. By changing the input negative-sequence reactive power instruction, the amplitude of the negative-sequence voltage output by the converter is adjusted, thereby changing the negative-sequence reactive power transmitted between the converter and the grid. PI control achieves zero-static-error regulation. Under the premise that the negative-sequence reactive power instruction does not exceed the limit, the negative-sequence reactive power transmitted between the converter and the grid can follow.

[0070] Specifically, if Figure 2 As shown, the negative sequence voltage reference value of the converter is Vgn_ref is equal to the negative sequence voltage amplitude of the power grid obtained after sequence decomposition V sn. By detecting the input negative sequence reactive power command qg_ref and the reactive power fed back by the negative sequence active / reactive power measurement module qg The deviation between them is calculated by using the PI control strategy to obtain the per-unit value of the converter voltage amplitude deviation Δvgn_pu, and finally the converter voltage amplitude Vgn is obtained.

[0071] like Figure 3 As shown, by detecting the input negative sequence active power command p g_ref and the active power fed back by the negative sequence active / reactive power measurement module p The deviation between g and the per-unit value of the converter frequency deviation Δ is obtained by using the droop control strategy. f g _ pu, according to the "active power-frequency" droop characteristic curve of the synchronous generator, that is, the frequency of the negative sequence voltage is opposite to that of the positive sequence, so p - f The droop relationship is opposite, and the phase angle of the converter output voltage is finally obtained by integration. θ gn, thereby changing the negative sequence active power transmitted between the converter and the grid p g. The formula for this process is expressed as .

[0072] Then, the three-phase switching signals of the grid-type converter are generated through PWM modulation.

[0073] Step 4: When a fault occurs, the grid-side three-phase voltage signal and the three-phase current signal are subjected to three-phase voltage and current sequence decomposition to obtain the amplitude of the negative-sequence voltage of the converter, the phase of the negative-sequence voltage, the amplitude of the negative-sequence current, and the phase of the negative-sequence current, including: using the Fourier method to extract the amplitude and initial phase angle of the grid-side three-phase voltage signal, the converter voltage signal, and the converter output current signal, and then writing the obtained amplitude and phase in the form of a complex exponential expression, and subjecting the complex exponential form of the three-phase voltage and current to the matrix transformation described in formula (1) to obtain the complex exponential form of the decomposed positive and negative zero-sequence components, and extracting the amplitude and phase of the required negative-sequence voltage component and negative-sequence current component.

[0074] Specifically, the three-phase voltage on the grid side after the fault occurs v sabc , converter voltage v gabc and converter current i gabc As the input signal, the amplitude and phase angle of the three-phase voltage or current are first obtained by the Fourier module, and then the amplitude of the negative sequence component of the asymmetric three-phase voltage of the power grid is obtained after the sequence decomposition operation. Vsn and phase angle θ sn , the amplitude of the negative sequence component of the converter voltage V gn and phase angle θ gn And the amplitude of the negative sequence component of the converter output current I gn and phase angle θ gi The specific sequence decomposition operation is shown in the following formula:

[0075] (5)

[0076] Among them, subscript 0 represents the zero sequence component, subscript 1 represents the positive sequence component, and subscript 2 represents the negative sequence component. α=ej 2π / 3.

[0077] Step 5: Power measurement is performed based on the amplitude and phase of the negative-sequence voltage output by the converter, the amplitude of the negative-sequence current, and the phase of the negative-sequence current to obtain the negative-sequence active power and reactive power transmitted between the converter and the grid, thereby completing the negative-sequence power control of the converter, including: performing a dq / abc inverse transformation on the amplitude and phase of the negative-sequence voltage component and the negative-sequence current component to obtain the negative-sequence three-phase current, and then performing an abc / dq transformation to obtain the converter d-axis current and q-axis current in a two-phase synchronous rotating coordinate system with the phase of the converter negative-sequence voltage component as a reference, and respectively calculating the negative-sequence active power and negative-sequence reactive power transmitted between the converter and the grid in the two-phase synchronous rotating coordinate system.

[0078] Specifically, if Figure 6 As shown, the power measurement module is used for power measurement, and the input of the module is the negative sequence voltage amplitude signal of the converter. V gn, negative sequence voltage phase signal θ gn, negative sequence current amplitude signal I gn and negative sequence current phase signals θ gi. v d. v q are the converter d Shaft voltage and q Shaft voltage, where v d= V gn, v q=0; input negative sequence current amplitude signal I gn and negative sequence current phase signals θ gi is transformed by dq / abc to obtain the negative sequence three-phase current i gnabc, and then through abc / dq transformation, the converter in the two-phase synchronous rotating coordinate system with the converter negative sequence voltage phase as the reference is obtained d Shaft current id and q Shaft current i q. Calculate the negative sequence active power transmitted between the converter and the grid in a two-phase synchronous rotating coordinate system. p g and negative sequence reactive power q g. The calculation formula is as follows:

[0079] (6)

[0080] As an example, Figure 7 、 Figure 8 as well as Figure 9 As shown, it is q g_ref< q g_min_n, p g_ref> p The simulation result of the transient instability of negative sequence voltage and power angle occurs at the same time at g_max_n. At this time, the amplitude of the negative sequence component of the converter voltage is V gn will first decrease to 0 and then increase in the opposite direction, making the active power transmitted between the converter and the grid p g and reactive power q g is not under control and may eventually lead to system crash.

[0081] like Figure 10 、 Figure 11 as well as Figure 12 As shown, it is adjusted q g_ref and p g_ref makes q g_ref= q g_min_n, p g_ref= p The simulation results show that the negative sequence voltage and power angle transient instability do not occur at g_max_n. At this time, the amplitude of the negative sequence component of the converter voltage is V gn eventually stabilizes after a period of time, and the active power transmitted between the converter and the grid p g and reactive power q g are controlled at reference values p g_ref and q g_ref.

[0082] Example 2

[0083] In one embodiment of the present disclosure, a negative-sequence voltage control system for a grid-connected converter is provided, characterized by comprising:

[0084] Grid connection initialization module, used to build the topology structure of grid-connected converter and grid;

[0085] The negative-sequence power calculation and comparison module is used to obtain the rated phase voltage of the grid-connected converter, the grid voltage amplitude, and the voltage amplitude of the grid-connected converter. Based on the rated phase voltage of the converter, the grid voltage amplitude, and the converter voltage amplitude, it calculates the negative-sequence reactive power absorbed by the converter and the maximum negative-sequence reactive power that can be absorbed under the specified fault condition, compares the two, and outputs the negative-sequence active power command and the negative-sequence reactive power command;

[0086] The negative-sequence active power control module and the negative-sequence reactive power control module are used to perform droop control using the negative-sequence active power command, adjusting the phase angle of the converter output negative-sequence voltage by changing the input negative-sequence active power command; perform PI control using the negative-sequence reactive power command, adjusting the amplitude of the converter output negative-sequence voltage by changing the input negative-sequence reactive power command; and then generate the three-phase switching signal of the grid-type converter by PWM modulation of the phase angle and amplitude of the negative-sequence voltage;

[0087] The three-phase voltage and current sequence decomposition module is used to perform three-phase voltage and current sequence decomposition on the grid-side three-phase voltage signal and three-phase current signal when a fault occurs, and obtain the amplitude and phase of the negative sequence voltage of the converter, the amplitude and phase of the negative sequence current;

[0088] The power measurement module is used to measure power based on the amplitude and phase of the negative-sequence voltage, the amplitude and phase of the negative-sequence current output by the converter, obtain the negative-sequence active power and reactive power transmitted between the converter and the power grid, and complete the negative-sequence power control of the converter.

[0089] As an embodiment, the power control module includes a negative sequence reactive power control module and a negative sequence active power control module. The negative sequence reactive power control module adopts PI control, and the negative sequence active power control module adopts droop control. The appropriate q g_ref and p g_ref The voltage is input to the negative sequence reactive power control module and the negative sequence active power control module respectively, and the amplitude of the converter output voltage under the corresponding power instruction is obtained after corresponding control. V gn and phase θ gn , and then generate the three-phase switching signal of the grid-type converter through PWM modulation.

[0090] The power measurement module is a negative sequence active / reactive power measurement module. When a fault occurs, the grid side voltage v sabc The amplitude of the negative sequence voltage of the fault power grid is obtained by the three-phase voltage sequence decomposition module V sn and phase θsn , converter voltage v gabc The amplitude of the converter negative sequence voltage is obtained by the three-phase voltage and current sequence decomposition module V gn and phase θ gn ;Converter output current i gabc The amplitude of the converter output negative sequence current is obtained through the three-phase voltage and current sequence decomposition module I gn and phase θ gi The negative sequence active / reactive power measurement module can measure the negative sequence active power transmitted between the converter and the grid. p g and reactive power q g .

[0091] Example 3

[0092] In one embodiment of the present disclosure, a computer program product is provided, including a computer program. When the computer program is executed by a processor, the method for controlling negative sequence voltage of a grid-connected converter is implemented.

[0093] Example 4

[0094] In one embodiment of the present disclosure, a non-transitory computer-readable storage medium is provided, wherein the non-transitory computer-readable storage medium is used to store computer instructions. When the computer instructions are executed by a processor, the negative-sequence voltage control method of a grid-type converter is implemented.

[0095] Example 5

[0096] In one embodiment of the present disclosure, an electronic device is provided, comprising: a processor, a memory, and a computer program; wherein the processor is connected to the memory, and the computer program is stored in the memory. When the electronic device is running, the processor executes the computer program stored in the memory, so that the electronic device executes the negative-sequence voltage control method of a grid-type converter.

[0097] The present disclosure is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present disclosure. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0098] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0099] Although the above describes the specific implementation methods of the present disclosure in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present disclosure. Those skilled in the art should understand that on the basis of the technical solution of the present disclosure, various modifications or variations that can be made by those skilled in the art without creative work are still within the scope of protection of the present disclosure.

Claims

1. A negative sequence voltage control method for a grid-connected converter, characterized in that: include: Constructing a topological structure for connecting the grid-connected converter to the power grid; Obtain the rated phase voltage of the grid-connected converter, the grid voltage amplitude, and the voltage amplitude of the grid-connected converter. Based on the rated phase voltage of the converter, the grid voltage amplitude, and the converter voltage amplitude, calculate the negative-sequence reactive power absorbed by the converter and the maximum negative-sequence reactive power that can be absorbed under the specified fault condition, compare the two, and output a negative-sequence active power command and a negative-sequence reactive power command. The negative-sequence active power command is used for droop control, and the phase angle of the converter output negative-sequence voltage is adjusted by changing the input negative-sequence active power command. The negative-sequence reactive power command is used for PI control, and the amplitude of the converter output negative-sequence voltage is adjusted by changing the input negative-sequence reactive power command. The phase angle and amplitude of the negative-sequence voltage are then modulated by PWM to generate the three-phase switching signal of the grid-type converter. When a fault occurs, the three-phase voltage and current signals on the grid side are decomposed into three-phase voltage and current sequence to obtain the amplitude and phase of the negative sequence voltage, the amplitude and phase of the negative sequence current of the converter; Power measurement is performed based on the amplitude and phase of the negative-sequence voltage, the amplitude of the negative-sequence current, and the phase of the negative-sequence current output by the converter to obtain the negative-sequence active power and reactive power transmitted between the converter and the grid, thereby completing the negative-sequence power control of the converter.

2. The negative sequence voltage control method of a grid-connected converter according to claim 1, characterized in that: Based on the rated phase voltage of the converter, the grid voltage amplitude, and the converter voltage amplitude, the negative-sequence reactive power absorbed by the converter that meets the set requirements under the specified fault condition is calculated; the converter has a certain limit on the absorption of negative-sequence reactive power, and once the limit is exceeded, transient voltage instability will occur. Based on the transmission model of the negative-sequence active power and negative-sequence reactive power exchanged between the converter and the grid, the maximum negative-sequence reactive power that the converter can absorb under this fault condition is calculated, and the negative-sequence reactive power absorbed by the converter that meets the set requirements is compared with the maximum negative-sequence reactive power that can be absorbed. The active power command and reactive power command are further adjusted to ensure that the power command does not exceed the limit.

3. The negative sequence voltage control method of a grid-connected converter according to claim 1, characterized in that: The negative-sequence active power command is used for droop control. According to the active-frequency droop characteristic curve of the synchronous generator, the phase angle of the negative-sequence voltage output by the converter is adjusted by changing the input negative-sequence active power command, thereby changing the negative-sequence active power transmitted between the converter and the grid.

4. The negative sequence voltage control method of a grid-connected converter according to claim 1, wherein: PI control is performed using the negative-sequence reactive power instruction. By changing the input negative-sequence reactive power instruction, the amplitude of the negative-sequence voltage output by the converter is adjusted, thereby changing the negative-sequence reactive power transmitted between the converter and the grid. PI control achieves zero-static-error regulation. Under the premise that the negative-sequence reactive power instruction does not exceed the limit, the negative-sequence reactive power transmitted between the converter and the grid can follow.

5. The negative sequence voltage control method of a grid-connected converter according to claim 1, characterized in that: When a fault occurs, the grid-side three-phase voltage signal and the three-phase current signal are subjected to three-phase voltage and current sequence decomposition, including: using the Fourier method to extract the amplitudes and initial phase angles of the grid-side three-phase voltage signal, the converter voltage signal, and the converter output current signal, respectively; then the obtained amplitudes and phases are written in the form of complex exponential expressions; the complex exponential forms of the three-phase voltage and current are subjected to matrix transformation to obtain the complex exponential forms of the decomposed positive and negative zero-sequence components; and the amplitudes and phases of the required negative-sequence voltage components and negative-sequence current components are extracted.

6. The negative sequence voltage control method of a grid-connected converter according to claim 5, characterized in that: The amplitude and phase of the negative sequence voltage component and the negative sequence current component are transformed by dq / abc inverse transformation to obtain the negative sequence three-phase current, and then the abc / dq transformation is performed to obtain the converter in the two-phase synchronous rotating coordinate system with the phase of the converter negative sequence voltage component as the reference. d Shaft current and q The negative-sequence active power and negative-sequence reactive power transmitted between the converter and the grid are calculated in a two-phase synchronous rotating coordinate system.

7. A negative sequence voltage control system for a grid-connected converter, characterized in that: include: Grid connection initialization module, used to build the topology structure of grid-connected converter and grid; The negative-sequence power calculation and comparison module is used to obtain the rated phase voltage of the grid-connected converter, the grid voltage amplitude, and the voltage amplitude of the grid-connected converter. Based on the rated phase voltage of the converter, the grid voltage amplitude, and the converter voltage amplitude, it calculates the negative-sequence reactive power absorbed by the converter and the maximum negative-sequence reactive power that can be absorbed under the specified fault condition, compares the two, and outputs the negative-sequence active power command and the negative-sequence reactive power command; The negative-sequence active power control module and the negative-sequence reactive power control module are used to perform droop control using the negative-sequence active power command, adjusting the phase angle of the converter output negative-sequence voltage by changing the input negative-sequence active power command; perform PI control using the negative-sequence reactive power command, adjusting the amplitude of the converter output negative-sequence voltage by changing the input negative-sequence reactive power command; and then generate the three-phase switching signal of the grid-type converter by PWM modulation of the phase angle and amplitude of the negative-sequence voltage; The three-phase voltage and current sequence decomposition module is used to perform three-phase voltage and current sequence decomposition on the grid-side three-phase voltage signal and three-phase current signal when a fault occurs, and obtain the amplitude and phase of the negative sequence voltage of the converter, the amplitude and phase of the negative sequence current; The power measurement module is used to measure power based on the amplitude and phase of the negative-sequence voltage output by the converter, the amplitude of the negative-sequence current, and the phase of the negative-sequence current, to obtain the negative-sequence active power and reactive power transmitted between the converter and the power grid, and to complete the negative-sequence power control of the converter.

8. A computer program product comprising a computer program, characterized in that When the computer program is executed by a processor, the negative sequence voltage control method of a grid-type converter according to any one of claims 1 to 6 is implemented.

9. A non-transitory computer-readable storage medium, characterized in that The non-transitory computer-readable storage medium is used to store computer instructions. When the computer instructions are executed by the processor, the negative-sequence voltage control method of the grid-type converter according to any one of claims 1 to 6 is implemented.

10. An electronic device, characterized in that: include: A processor, a memory, and a computer program; wherein the processor is connected to the memory, the computer program is stored in the memory, and when the electronic device is running, the processor executes the computer program stored in the memory to enable the electronic device to implement a negative-sequence voltage control method for a grid-type converter as described in any one of claims 1 to 6.

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