Short-circuit current suppression method and device based on saturation current angle modulation, terminal equipment and computer readable storage medium

Abstract

The invention discloses a short-circuit current suppression method and device based on saturation current angle modulation, terminal equipment and a computer readable storage medium, and the method comprises the steps: obtaining an electric power parameter and a topological structure of an offshore wind power grid-connected system, and building a mathematical model of the offshore wind power grid-connected system; monitoring whether the current amplitude at the outlet side of the fan exceeds a preset amplitude or not; if the current amplitude at the outlet side of the fan does not exceed the preset amplitude, controlling the saturation current angle of the current of the converter to be synchronous with the angle provided by the VSG; and if the current amplitude of the outlet side of the fan exceeds the preset amplitude, calculating a target saturation current angle corresponding to the minimum short-circuit current after current limiting according to the mathematical model of the offshore wind power grid-connected system, and controlling the converter to adjust the saturation current angle to the target saturation current angle, so that the short-circuit current after current limiting is minimum. By implementing the invention, the amplitude of the short-circuit current can be suppressed, and the stability of the grid-connected system is improved.

Description

Technical Field

[0001] The present invention relates to the field of electric power technology, and in particular to a short-circuit current suppression method based on saturation current angle modulation. Background Art

[0002] As offshore wind power is gradually connected to the grid, the proportion of power electronic equipment in the system continues to increase. Short-circuit currents in fault conditions can endanger the safety of the converter and even the entire system. Short-circuit current refers to the high current that flows through the fault point when a grid fault occurs. When the short-circuit current flows through the grid-connected converter, it may cause equipment overload, temperature rise, or even burnout, thus affecting the normal operation of the system. In addition, excessive short-circuit currents may also cause serious damage to other system components and equipment, and have an adverse effect on the safety and reliability of the entire system. In this context, it has become very necessary to study the short-circuit current suppression method for the system of offshore wind power connected to the grid via a grid-connected converter. Summary of the invention

[0003] The embodiments of the present invention provide a short-circuit current suppression method, apparatus, terminal equipment and computer-readable storage medium based on saturation current angle modulation, which can suppress the amplitude of the short-circuit current and improve the stability of the grid-connected system.

[0004] An embodiment of the present invention provides a short-circuit current suppression method based on saturation current angle modulation, comprising:

[0005] Obtain the power parameters and topology of the offshore wind power grid-connected system;

[0006] Establish a mathematical model of offshore wind power grid-connected system based on power parameters and topological structure;

[0007] Monitor whether the current amplitude at the fan outlet side exceeds the preset amplitude;

[0008] If the current amplitude at the wind turbine outlet does not exceed the preset amplitude, the saturation current angle of the converter current is controlled to be synchronized with the angle provided by the VSG;

[0009] If the current amplitude at the wind turbine outlet exceeds the preset amplitude, the target saturation current angle corresponding to the minimum short-circuit current after current limiting is calculated according to the mathematical model of the offshore wind power grid-connected system, and the converter is controlled to adjust the saturation current angle to the target saturation current angle so that the short-circuit current after current limiting is minimized.

[0010] Furthermore, the target saturation current angle is opposite to the angle provided by the VSG.

[0011] Furthermore, the mathematical model of the offshore wind power grid-connected system is as follows:

[0012]

[0013] Among them, θ c represents the angle provided by VSG, ω c represents the angular velocity of the inverter, ω s represents the rated angular frequency of the system, H represents the inertia constant, Indicates the reference active power of the converter, P c It represents the actual output active power of the converter, and D represents the damping coefficient of VSG.

[0014] Furthermore, the short-circuit current is minimal, specifically:

[0015]

[0016] Among them, |I n | represents the short-circuit current amplitude, U s Indicates the system side outlet voltage, Indicates the maximum value of the converter current amplitude, R f Indicates the transition resistance at the fault point.

[0017] Furthermore, the short-circuit current suppression method based on saturation current angle modulation also includes:

[0018] Obtaining the voltage and current at the converter outlet;

[0019] According to the voltage and current at the converter outlet, the predicted value of the circuit reactance from the converter outlet to the fault point is calculated through the relationship of the mathematical model of the offshore wind power grid-connected system;

[0020] The circuit reactance prediction value is compared with the reactance value of each line in the grid-connected system, and the position corresponding to the line reactance value within the preset range of the circuit reactance prediction value is regarded as the fault position.

[0021] Based on the above method embodiment, the present invention provides a corresponding device embodiment, including: a power parameter acquisition module, a mathematical model construction module, a current amplitude monitoring module, a virtual synchronization control module, and a current limiting module;

[0022] The power parameter acquisition module is used to obtain the power parameters and topology of the offshore wind power grid-connected system;

[0023] Mathematical model building module, used to establish the mathematical model of offshore wind power grid-connected system according to power parameters and topological structure;

[0024] A current amplitude monitoring module is used to monitor whether the current amplitude at the fan outlet side exceeds a preset amplitude;

[0025] A virtual synchronization control module is used to control the saturation current angle of the converter current to be synchronized with the angle provided by the VSG if the current amplitude at the outlet side of the wind turbine does not exceed the preset amplitude;

[0026] The current limiting module is used to calculate the target saturation current angle corresponding to the minimum short-circuit current after current limiting according to the mathematical model of the offshore wind power grid-connected system if the current amplitude at the wind turbine outlet side exceeds the preset amplitude, and control the converter to adjust the saturation current angle to the target saturation current angle so that the short-circuit current after current limiting is minimized.

[0027] Furthermore, the target saturation current angle is opposite to the angle provided by the VSG.

[0028] Furthermore, the short-circuit current suppression device based on saturation current angle modulation further includes: a fault location module;

[0029] A fault location module, comprising: a converter voltage and current acquisition unit, a fault point prediction reactance calculation unit, and a fault location determination unit;

[0030] A converter voltage and current acquisition unit, used to acquire the voltage and current at the converter outlet;

[0031] The fault point prediction reactance calculation unit is used to calculate the predicted value of the circuit reactance from the converter outlet to the fault point according to the voltage and current at the converter outlet through the relationship of the offshore wind power grid-connected system mathematical model;

[0032] The fault position determination unit is used to compare the circuit reactance prediction value with the reactance value of each line in the grid-connected system, and regard the position corresponding to the line reactance value within the preset range of the circuit reactance prediction value as the fault position.

[0033] Based on the above-mentioned method embodiment, the present invention provides a corresponding terminal device embodiment, including: a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, the steps of the short-circuit current suppression method based on saturation current angle modulation as described in the present invention are implemented.

[0034] Based on the above-mentioned method embodiment, the present invention provides a corresponding computer-readable storage medium embodiment, including: a stored computer program, which controls the device where the computer-readable storage medium is located to execute the steps of the short-circuit current suppression method based on saturation current angle modulation as described in the present invention when the computer program is running.

[0035] Compared with the prior art, the beneficial effects of the embodiment of this solution are:

[0036] The present invention establishes a mathematical model of an offshore wind power grid-connected system through power parameters and topological structures, and obtains and monitors in real time whether the current amplitude at the outlet side of the wind turbine exceeds a preset threshold value. If the current amplitude at the outlet side of the wind turbine does not exceed the preset threshold value, it means that the wind turbine in the current system is operating normally and the current amplitude is within a preset safety range. The saturation current angle of the converter current is controlled to be synchronized with the angle provided by the VSG to ensure that the distribution and flow direction of the current in the system are consistent with the VSG, thereby reducing the impact of the short-circuit current; if the current amplitude at the outlet side of the wind turbine exceeds the preset threshold value, it means that the power equipment is bearing a current exceeding its rated load, which may cause a short-circuit current. In this case, the target saturation current angle corresponding to the minimum short-circuit current after current limiting is calculated through the operation relationship of the mathematical model of the offshore wind power grid-connected system, and the grid-connected system is current-limited, that is, the converter is controlled to adjust the saturation current angle. By adjusting the saturation current angle, the phase difference between the output current and the voltage of the converter is changed, thereby affecting the size of the short-circuit current. When the saturation current angle of the converter is adjusted to the target saturation current angle, the short-circuit current reaches a minimum value, thereby achieving the effect of maximally suppressing the short-circuit current.

[0037] In summary, the present invention controls the phase difference and amplitude of the short-circuit current by controlling the saturation current angle of the converter, thereby suppressing the amplitude of the short-circuit current and improving the stability of the grid-connected system. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a flow chart of a short-circuit current suppression method based on saturation current angle modulation provided by an embodiment of the present invention;

[0039] Figure 2 is a topological diagram of an offshore wind power transmission system provided by an embodiment of the present invention;

[0040] Figure 3 is a system control block diagram based on saturation current angle modulation provided by an embodiment of the present invention;

[0041] Figure 4 is a graph showing a current variation over time based on saturation current angle modulation provided by an embodiment of the present invention;

[0042] Figure 5 is a curve diagram of current variation over time based on VSG virtual synchronous control provided by an embodiment of the present invention;

[0043] Figure 6 It is a structural schematic diagram of a short-circuit current suppression device based on saturation current angle modulation provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] like Figure 1 As shown, an embodiment of the present invention provides a short-circuit current suppression method based on saturation current angle modulation, the method comprising at least the following steps:

[0046] Step S1: Obtaining power parameters and topology of the offshore wind power grid-connected system;

[0047] For step S1, in order to establish a mathematical model of the offshore wind power grid-connected system, it is necessary to collect power parameters and topological structure information. First, collect parameters such as the grid voltage, converter voltage, grid-connected system capacity, and grid-connected system angular velocity of the grid-connected system as shown in Table 1. Then, preprocess the collected data to remove outliers, fill in missing values, and perform filtering and other operations to ensure the accuracy and completeness of the data. At the same time, obtain the topological structure information of the wind farm, including the connection relationship between wind turbines, transformers, cables, and switchgear, organize and clean the topological structure information, ensure that the connection relationship between each device is accurate, and obtain the following: Figure 2 The topology diagram of the offshore wind power transmission system is shown.

[0048] Table 1

[0049]

[0050]

[0051] Step S2: Establishing a mathematical model of the offshore wind power grid-connected system according to power parameters and topological structure;

[0052] In a preferred embodiment, the mathematical model of the offshore wind power grid-connected system is specifically:

[0053]

[0054] Among them, θ c represents the angle provided by VSG, ω c represents the angular velocity of the inverter, ω s represents the rated angular frequency of the system, H represents the inertia constant, Indicates the reference active power of the converter, P c It represents the actual output active power of the converter, and D represents the damping coefficient of VSG.

[0055] For step S2, the mathematical model of the offshore wind power grid-connected system is established through the power parameters collected in step S1 and the sorted topological structure information. Under normal circumstances, the offshore wind power grid-connected system adopts virtual synchronous generator (VSG) control, and the operating principle of virtual synchronous control can be described by equation (1).

[0056] It should be noted that virtual synchronous control (VSG) is a control strategy based on power balance and current balance, which is achieved by simulating the behavior of traditional synchronous generators. In traditional synchronous generators, there is a strong coupling between rotor speed and power output, while virtual synchronous control achieves power output regulation by controlling the speed. Specifically, virtual synchronous control simulates the rotational mass moment and saturation current angle of the synchronous generator, so that the wind turbine exhibits response characteristics similar to those of traditional synchronous generators when connected to the grid.

[0057] Step S3: monitor whether the current amplitude at the fan outlet side exceeds a preset amplitude;

[0058] For step S3, in order to monitor whether a short-circuit current occurs, the system installs a current sensor or other measuring device on the outlet side of the fan. The sensor collects the current signal on the outlet side of the fan, and obtains the current amplitude on the outlet side of the fan through processing steps such as amplification, filtering and sampling. At the same time, the system pre-sets a current amplitude threshold. In the embodiment of the present invention, the threshold is 1.0 pu (per unit), and the current amplitude on the outlet side of the fan is monitored in real time and compared with the preset amplitude of 1.0 pu to detect abnormal current conditions in a timely manner.

[0059] Step S4: If the current amplitude at the outlet side of the wind turbine does not exceed the preset amplitude, the saturation current angle of the converter current is controlled to be synchronized with the angle provided by the VSG;

[0060] For step S4, if the monitored current amplitude is less than or equal to the preset amplitude, it is considered that the current amplitude does not exceed the preset amplitude, and the system will continue to execute the virtual synchronous control strategy. According to the design of the virtual synchronous control, VSG will provide an angle signal as a reference angle to control the working parameters of the converter to adjust the saturation current angle, so that the saturation current angle of the converter is synchronized with the angle provided by the virtual synchronous control (VSG), thereby realizing power flow regulation and power quality control.

[0061] Step S5: If the current amplitude at the wind turbine outlet exceeds the preset amplitude, the target saturation current angle corresponding to the minimum short-circuit current after current limiting is calculated according to the mathematical model of the offshore wind power grid-connected system, and the converter is controlled to adjust the saturation current angle to the target saturation current angle so that the short-circuit current after current limiting is minimized.

[0062] In a preferred embodiment, the short-circuit current is minimized, specifically:

[0063]

[0064] Among them, |I n | represents the short-circuit current amplitude, U s Indicates the system side outlet voltage, Indicates the maximum value of the converter current amplitude, R f Indicates the transition resistance at the fault point.

[0065] In a preferred embodiment, the target saturation current angle is opposite to the angle provided by the VSG.

[0066] For step S5, if the monitored current amplitude is greater than the preset amplitude, it means that the current amplitude has increased beyond the expected safety range, and a fault has occurred somewhere in the system, resulting in the generation of a short-circuit current. Excessive short-circuit current will bring danger to the converter and affect the safe and stable operation of the system. In this case, in order to protect the system equipment and ensure the stable operation of the system, measures need to be taken to limit the current amplitude to avoid equipment damage or system failure. Therefore, the present invention controls the converter to adjust the saturation current angle to the target saturation current angle, so that the short-circuit current after current limiting is minimized, thereby limiting the amplitude of the short-circuit current and avoiding equipment damage or system failure.

[0067] Among them, the target saturation current angle is determined by:

[0068] First, the saturation current angle is adjusted by controlling the converter to increase the current phase difference, thereby reducing the amplitude of the short-circuit current. The current of the converter after adjustment is:

[0069]

[0070] In the formula, represents the current phasor at the converter outlet, Indicates the maximum value of the converter current amplitude, θ c represents the angle provided by VSG, represents the saturation current angle.

[0071] At the same time, after the converter adjusts the saturation current angle, the expressions of the converter voltage, active power and reactive power are:

[0072]

[0073] In the formula, represents the voltage phasor of the converter, Represents the voltage phasor at the fault point, U f Indicates the voltage amplitude at the fault point, δ fIndicates the voltage phase angle at the fault point, X m Indicates the line reactance from the converter outlet to the fault point, P c Indicates the output active power of the converter, Q c Indicates the reactive power output by the converter.

[0074] According to the power relationship in the mathematical model of the offshore wind power grid-connected system and the expressions of the voltage, active power and reactive power of the converter as shown in equation (4), the circuit equation after current limiting can be obtained:

[0075]

[0076] In the formula, represents the converter output voltage phasor, Represents the voltage phasor at the system side, R f Indicates the transition resistance at the fault point, X n Indicates the line reactance from the system outlet to the fault point, X s represents the internal reactance of the system, Indicates the current phasor at the system side output.

[0077] Through equations (5) and (7), the voltage at the converter outlet can be obtained: The expression is:

[0078]

[0079] It can be seen from formula (8) that the converter output voltage is also affected by the transition resistance and the opposite-end current. Combining formula (6) and formula (7), the expression of the opposite-end current can be obtained:

[0080]

[0081] Combining equations (8) and (9), the voltage at the converter outlet can be obtained: Expression variants of :

[0082]

[0083] Through equation (9) and equation (3), the variation of the current phasor at the system side outlet can be obtained:

[0084]

[0085] By changing the system side outlet current phasor of equation (11), the expression of short-circuit current can be obtained as follows:

[0086]

[0087] From the expression of short-circuit current in formula (12), it can be seen that when φ=-θ c, that is, when the saturation current angle is opposite to the angle provided by VS G, the short-circuit current is minimum.

[0088] Therefore, through the calculation of the mathematical model of the offshore wind power grid-connected system, the value of the target saturation current angle can be determined, and the converter can be controlled to adjust the saturation current angle to the target saturation current angle, so that the short-circuit current can be minimized.

[0089] like Figure 3 The figure shows the control block diagram of the system based on saturated current angle modulation, including VSG control loop, voltage control loop, current saturation algorithm module, current control loop and PWM modulation module. The VSG control loop simulates the synchronous machine so that the wind turbine has the inertia characteristics of the traditional synchronous machine when it is connected to the grid, and provides the system with a phase angle θ c , that is, the angle between the abc stationary coordinate system and the dq coordinate system. This phase angle provides a reference angle for subsequent Park transformation and inverse transformation. The system control based on the saturation current angle is mainly achieved through the voltage control loop, current saturation algorithm module, current control loop and PWM modulation module.

[0090] The voltage control loop is used to control the output voltage of the converter; the current saturation algorithm module is used to control the amplitude of the converter current. When the converter current amplitude exceeds the threshold, it switches to the current limiting mode and controls the current amplitude to I max , while passing the saturation current angle Realize the control of the dq components of the current to achieve the subsequent control purpose; the current control loop adjusts the saturation current angle according to the target saturation current angle output by the current saturation algorithm module, and generates a corresponding control signal by comparing the difference between the actual saturation current angle and the target saturation current angle, thereby adjusting the value of the saturation current angle to achieve current control; finally, the PWM modulation module receives the control signal of the current control loop and generates a PWM modulation waveform based on the signal. By adjusting the duty cycle and frequency of the PWM signal, the PWM modulation module controls the on and off time of the switching device, thereby achieving regulation of the output current of the converter.

[0091] In a preferred embodiment, the short-circuit current suppression method based on saturation current angle modulation further includes:

[0092] Obtaining the voltage and current at the converter outlet;

[0093] According to the voltage and current at the converter outlet, the predicted value of the circuit reactance from the converter outlet to the fault point is calculated through the relationship of the mathematical model of the offshore wind power grid-connected system;

[0094] The circuit reactance prediction value is compared with the reactance value of each line in the grid-connected system, and the position corresponding to the line reactance value within the preset range of the circuit reactance prediction value is regarded as the fault position.

[0095] The present invention can also determine the location of the fault by monitoring the voltage and current values ​​at the converter outlet. In one embodiment of the present invention, the voltage and current at the converter outlet are obtained by measuring or monitoring the device, and then the voltage and current at the converter outlet are substituted into formula (10), and the line reactance X from the converter outlet to the fault point is calculated according to the formula: m , X m The value is compared with the reactance value of each line in the grid-connected system, and the position corresponding to the line reactance value within the preset range of the circuit reactance prediction value is found, and it is regarded as the fault position.

[0096] By implementing the present invention, the fault location can be quickly and accurately determined while suppressing the short-circuit current, guiding the location and repair of the fault, and improving the reliability and stability of the offshore wind power grid-connected system.

[0097] In order to further verify the effectiveness of the short-circuit current suppression method of the present invention, the short-circuit current suppression method based on saturated current angle modulation is used to suppress the short-circuit current of the grid-connected system when a three-phase short-circuit fault occurs, and the following is obtained: Figure 4 The current versus time curve shown in Figure 4 It can be seen that a fault occurred in the grid-connected system at 3s, the current amplitude jumped and exceeded 1.0pu, generating a short-circuit current. The fault lasted for 50ms, and the maximum amplitude of the system short-circuit current was 1.2pu.

[0098] In order to compare the effect of the present invention on suppressing short-circuit current, only VSG virtual synchronous control is used for the grid-connected system with the same three-phase short-circuit fault, and the following is obtained: Figure 5 The current versus time curve shown in Figure 5 It can be observed that after the fault occurred, the short-circuit current of the system exceeded 1.4pu, which may cause damage to power equipment such as transformers that are sensitive to current shocks and affect the safe and stable operation of the system.

[0099] In summary, by comparing Figure 4 and Figure 5 It can be determined that the short-circuit current suppression method based on saturation current angle modulation proposed in the present invention effectively suppresses the amplitude of the short-circuit current.

[0100] like Figure 6 As shown, based on the above method embodiment, a corresponding device embodiment is provided;

[0101] An embodiment of the present invention provides a short-circuit current suppression device based on saturation current angle modulation, comprising: a power parameter acquisition module, a mathematical model construction module, a current amplitude monitoring module, a virtual synchronization control module, and a current limiting module;

[0102] The power parameter acquisition module is used to obtain the power parameters and topology of the offshore wind power grid-connected system;

[0103] Mathematical model building module, used to establish the mathematical model of offshore wind power grid-connected system according to power parameters and topological structure;

[0104] A current amplitude monitoring module is used to monitor whether the current amplitude at the fan outlet side exceeds a preset amplitude;

[0105] A virtual synchronization control module is used to control the saturation current angle of the converter current to be synchronized with the angle provided by the VSG if the current amplitude at the outlet side of the wind turbine does not exceed the preset amplitude;

[0106] The current limiting module is used to calculate the target saturation current angle corresponding to the minimum short-circuit current after current limiting according to the mathematical model of the offshore wind power grid-connected system if the current amplitude at the wind turbine outlet side exceeds the preset amplitude, and control the converter to adjust the saturation current angle to the target saturation current angle so that the short-circuit current after current limiting is minimized.

[0107] In a preferred embodiment, the short-circuit current suppression device based on saturation current angle modulation further includes: a fault location module;

[0108] A fault location module, comprising: a converter voltage and current acquisition unit, a fault point prediction reactance calculation unit, and a fault location determination unit;

[0109] A converter voltage and current acquisition unit, used to acquire the voltage and current at the converter outlet;

[0110] The fault point prediction reactance calculation unit is used to calculate the predicted value of the circuit reactance from the converter outlet to the fault point according to the voltage and current at the converter outlet through the relationship of the offshore wind power grid-connected system mathematical model;

[0111] The fault position determination unit is used to compare the circuit reactance prediction value with the reactance value of each line in the grid-connected system, and regard the position corresponding to the line reactance value within the preset range of the circuit reactance prediction value as the fault position.

[0112] It can be understood that the above-mentioned device item embodiment corresponds to the method item embodiment of the present invention, which can implement the short-circuit current suppression method based on saturation current angle modulation provided by any one of the above-mentioned method item embodiments of the present invention.

[0113] It should be noted that the device embodiments described above are merely illustrative, and some or all of the modules may be selected according to actual needs to achieve the purpose of the present embodiment. In addition, in the accompanying drawings of the device embodiments provided by the present invention, the connection relationship between the modules indicates that there is a communication connection between them, which may be specifically implemented as one or more communication buses or signal lines. Those of ordinary skill in the art may understand and implement the present invention without creative work.

[0114] Based on the above-mentioned embodiment of the short-circuit current suppression method based on saturation current angle modulation, another embodiment of the present invention provides a terminal device, which includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, the short-circuit current suppression method based on saturation current angle modulation of any embodiment of the present invention is implemented.

[0115] Exemplarily, in this embodiment, the computer program may be divided into one or more modules, which are stored in the memory and executed by the processor to implement the present invention. The one or more module elements may be a series of computer program instruction segments capable of implementing specific functions, which are used to describe the execution process of the computer program in the terminal device.

[0116] The terminal device may be a computing device such as a desktop computer, a notebook, a PDA, a cloud server, etc. The terminal device may include, but is not limited to, a processor and a memory.

[0117] The processor may be a central processing unit (CPU), other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or any conventional processor, etc. The processor is the control center of the terminal device, and uses various interfaces and lines to connect various parts of the entire terminal device.

[0118] Based on the above method embodiment, another embodiment is provided: another embodiment of the present invention provides a computer-readable storage medium, including a stored computer program, wherein when the computer program is running, the device where the computer-readable storage medium is located is controlled to execute the short-circuit current suppression method based on saturation current angle modulation described in any one of the above method embodiments of the present invention.

[0119] Wherein, the module / unit integrated with the short-circuit current suppression device / terminal equipment based on saturation current angle modulation, if implemented in the form of a software functional unit and sold or used as an independent product, can be stored in a computer-readable storage medium. Based on such an understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of the above-mentioned various method embodiments when executed by the processor. Wherein, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form, etc. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM, Read-Only Memory), random access memory (R AM, Random Access Memory), electrical carrier signal, telecommunication signal and software distribution medium, etc.

[0120] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A short-circuit current suppression method based on saturation current angle modulation, applicable to the wind turbine side converter of an offshore wind power grid-connected system, characterized in that: include: Obtain the power parameters and topology of the offshore wind power grid-connected system; Establishing a mathematical model of an offshore wind power grid-connected system according to the power parameters and topological structure; Monitor whether the current amplitude at the fan outlet side exceeds the preset amplitude; If the current amplitude at the outlet side of the wind turbine does not exceed the preset amplitude, the saturation current angle of the converter current is controlled to be synchronized with the angle provided by the VSG; If the current amplitude at the wind turbine outlet exceeds the preset amplitude, the target saturation current angle corresponding to the minimum short-circuit current after current limiting is calculated according to the mathematical model of the offshore wind power grid-connected system, and the converter is controlled to adjust the saturation current angle to the target saturation current angle so that the short-circuit current after current limiting is minimized.

2. The short-circuit current suppression method based on saturation current angle modulation according to claim 1, characterized in that: The target saturation current angle is opposite to the angle provided by the VSG.

3. The short-circuit current suppression method based on saturation current angle modulation according to claim 2, characterized in that: The mathematical model of the offshore wind power grid-connected system is specifically: Among them, θ c represents the angle provided by VSG, ω c represents the angular velocity of the inverter, ω s represents the rated angular frequency of the system, H represents the inertia constant, Indicates the reference active power of the converter, P c It represents the actual output active power of the converter, and D represents the damping coefficient of VSG.

4. The short-circuit current suppression method based on saturation current angle modulation according to claim 3 is characterized in that: The short-circuit current is the minimum, specifically: Among them, |I n | represents the short-circuit current amplitude, U s Indicates the system side outlet voltage, Indicates the maximum value of the converter current amplitude, R f Indicates the transition resistance at the fault point.

5. The short-circuit current suppression method based on saturation current angle modulation according to claim 4, characterized in that: Also includes: Obtaining the voltage and current at the converter outlet; According to the voltage and current at the converter outlet, through the relationship of the offshore wind power grid-connected system mathematical model, a predicted value of the circuit reactance from the converter outlet to the fault point is calculated; The circuit reactance prediction value is compared with the reactance value of each line in the grid-connected system, and the position corresponding to the line reactance value within the preset range of the circuit reactance prediction value is regarded as the fault position.

6. A short-circuit current suppression device based on saturation current angle modulation, characterized in that: include: Power parameter acquisition module, mathematical model building module, current amplitude monitoring module, virtual synchronization control module, and current limiting module; The power parameter acquisition module is used to acquire the power parameters and topology of the offshore wind power grid-connected system; The mathematical model building module is used to establish a mathematical model of the offshore wind power grid-connected system according to the power parameters and topological structure; The current amplitude monitoring module is used to monitor whether the current amplitude at the fan outlet side exceeds a preset amplitude; The virtual synchronization control module is used to control the saturation current angle of the converter current to be synchronized with the angle provided by the VSG if the current amplitude at the outlet side of the wind turbine does not exceed the preset amplitude; The current limiting module is used to calculate the target saturation current angle corresponding to the minimum short-circuit current after current limiting according to the mathematical model of the offshore wind power grid-connected system if the current amplitude at the wind turbine outlet side exceeds the preset amplitude, and control the converter to adjust the saturation current angle to the target saturation current angle so that the short-circuit current after current limiting is minimized.

7. The short-circuit current suppression device based on saturation current angle modulation according to claim 6, characterized in that: The target saturation current angle is opposite to the angle provided by the VSG.

8. The short-circuit current suppression device based on saturation current angle modulation according to claim 7, characterized in that: Also includes: Fault location module; The fault location module includes: a converter voltage and current acquisition unit, a fault point prediction reactance calculation unit, and a fault location determination unit; The converter voltage and current acquisition unit is used to acquire the voltage and current at the converter outlet; The fault point prediction reactance calculation unit is used to calculate the circuit reactance prediction value from the converter outlet to the fault point according to the voltage and current at the converter outlet through the relationship of the offshore wind power grid-connected system mathematical model; The fault position determination unit is used to compare the circuit reactance prediction value with the reactance value of each line in the grid-connected system, and regard the position corresponding to the line reactance value within the preset range of the circuit reactance prediction value as the fault position.

9. A terminal device, characterized in that: The method comprises a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, the short-circuit current suppression method based on saturation current angle modulation as described in any one of claims 1 to 5 is implemented.

10. A computer-readable storage medium, characterized in that: include: A stored computer program, wherein when the computer program is executed, the device where the computer-readable storage medium is located is controlled to execute the short-circuit current suppression method based on saturation current angle modulation as described in any one of claims 1 to 5.

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