Cooperative control method and system for voltage, storage medium and equipment

Abstract

The invention discloses a cooperative control method for voltage, which is used for a wind power plant direct current system, and comprises the following steps: when the wind power plant direct current system has a direct current commutation failure fault, determining whether the direct current commutation failure fault is in an overvoltage state or not according to the voltage of a commutation bus; if the wind power plant direct-current system is in the overvoltage state, reactive power needing to be absorbed by the wind power plant direct-current system is calculated according to the deviation between the commutation bus voltage and the reference voltage; calculating the maximum reactive power absorption power of each wind turbine generator in the direct current system of the wind power plant, distributing reactive power needing to be absorbed to each wind turbine generator according to the proportion of the reactive power capacity of the wind turbine generator to the total reactive power capacity of the wind power plant, and obtaining reactive power absorption reference power of each wind turbine generator; when the reactive power absorption reference power of any wind turbine generator reaches the maximum reactive power absorption power, residual reactive power in the reactive power needing to be absorbed is determined; and starting the static var generator SVG, and outputting residual reactive power through the static var generator SVG.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power system control, and in particular to a coordinated control method and system for voltage, a storage medium and equipment. BACKGROUND

[0002] In the wind power concentrated areas of northwest China and north China, the HVDC system based on line commutated converter (LCC) is widely used due to its high technical maturity, but this technology has inherent defects: when the receiving end AC system fails or the DC control is abnormal, the sending end converter station is prone to commutation failure, resulting in a sudden drop or even interruption of DC power. At this time, the active power of the sending end wind farm cannot be fed into the DC system in time, and the excess power surges into the AC power grid, causing the voltage of the commutation bus to rise sharply (transient overvoltage), which can be more than 1.3 times the rated voltage in severe cases. This kind of overvoltage can trigger the overvoltage protection action of the wind turbine, leading to cascading tripping of the wind turbine and even damage to the converter station equipment.

[0003] The existing overvoltage suppression means of the wind farm mainly relies on single device adjustment, and does not fully utilize the coordinated potential of the multi-source reactive power resources in the wind farm, making it difficult to quickly and accurately match the system reactive power demand in the transient process. SUMMARY

[0004] In view of this, it is necessary to propose a coordinated control method for voltage in view of the above problems.

[0005] A coordinated control method for voltage, which is used in a wind farm DC system, the wind farm includes a plurality of wind turbines, and the method comprises:

[0006] When the DC commutation failure fault occurs in the wind farm DC system, it is determined whether the DC commutation failure fault is in an overvoltage state according to the commutation bus voltage;

[0007] If the wind farm DC system is in an overvoltage state, the reactive power that needs to be absorbed by the wind farm DC system is calculated according to the deviation of the commutation bus voltage from the reference voltage;

[0008] The maximum reactive power absorption of each wind turbine in the wind farm DC system is calculated, and the reactive power that needs to be absorbed by each wind turbine is allocated according to the proportion of the reactive power capacity of the wind turbine in the total reactive power capacity of the wind farm, to obtain the reactive power absorption reference power of each wind turbine;

[0009] When the reactive power absorption reference power of any one wind turbine reaches the maximum reactive power absorption, the remaining reactive power in the reactive power that needs to be absorbed is determined;

[0010] A static var generator (SVG) is started, and the remaining reactive power is output through the static var generator (SVG).

[0011] In the scheme, when the commutation bus voltage of the wind farm DC system presents a three-phase symmetric characteristic, the amplitude of the commutation bus voltage is greater than a preset lower threshold of voltage amplitude, and the absolute value of the commutation bus voltage change rate is within a fixed range, it is determined that the DC system has a DC commutation failure fault.

[0012] In the scheme, the reactive power needed to be absorbed by the wind farm DC system is calculated according to the deviation of the commutation bus voltage from the reference voltage, and specifically includes:

[0013] The reactive power needed to be absorbed by the DC system Qdemand is calculated according to the following formula:

[0014] Q demand demand = K · (U p -U ref )

[0015] In the formula, U p is the commutation bus voltage; U ref is the reference voltage; and K is a proportional coefficient.

[0016] In the scheme, the maximum reactive power absorption of each wind turbine in the wind farm DC system is the absolute value of the maximum active power of a single wind turbine or the minimum reactive power of a single wind turbine.

[0017] In the scheme, the maximum active power of a single wind turbine is determined according to the maximum allowable current of a single wind turbine and the real-time voltage at the grid connection point of the single wind turbine:

[0018] P gmax = 3U g ·I gmax

[0019] In the formula, P gmax is the maximum active power of a single wind turbine; U g is the peak value of the real-time voltage at the grid connection point of the single wind turbine; and I gmax is the maximum allowable current of the single wind turbine.

[0020] In the scheme, the minimum reactive power of a single wind turbine is determined according to the current active power of the wind turbine, the real-time voltage at the grid connection point of the wind turbine, and the maximum allowable current of the wind turbine:

[0021]

[0022] In the formula, Q gmin is the minimum reactive power of a single wind turbine, P g is the current active power of the single wind turbine; m is a modulation coefficient; U g is the real-time voltage at the grid connection point of the wind turbine; and ωs is the synchronous electrical angular velocity; L g I is the inductance of the wind turbine line; gmax It is the maximum allowable current of a single wind turbine.

[0023] In the above solution, allocating reactive power to be absorbed to each wind turbine according to the ratio of the reactive capacity of the wind turbine to the total reactive capacity of the wind farm to obtain the reactive absorption reference power of each wind turbine specifically includes:

[0024] According to the minimum reactive power Q of a single wind turbine gmin and the maximum active power of a single wind turbine P gmax Determine the total reactive capacity Q of the wind farm wmax :

[0025]

[0026] Where Q wmax is the total reactive capacity of the wind farm; n is the number of wind turbines in the wind farm; P gmax is the maximum active power of a single unit; P g is the current active power of a single unit; Q gmin is the minimum reactive power of a single unit;

[0027] According to the converter capacity S of a single wind turbine g Accounting for the total capacity S of the wind turbine converter w The ratio of each wind turbine is used to obtain the reactive absorption reference power Q ref_wind :

[0028]

[0029] Where S g is the converter capacity of a single wind turbine; S w is the total capacity of the wind farm unit converter; Q wmax is the total reactive capacity of the wind farm; Q gmin It is the minimum reactive power of a single unit.

[0030] The present invention also proposes a coordinated control system for voltage, the system comprising: a fault judgment unit, a reactive power demand calculation unit, a reactive power distribution unit, a residual reactive power calculation unit and an SVG control unit;

[0031] The fault judgment unit is configured to, when a DC commutation failure fault is detected in the wind farm DC system, judge whether the fault is in an overvoltage state based on the commutation bus voltage;

[0032] The reactive power demand calculation unit is configured to calculate the reactive power that the DC system needs to absorb based on the deviation between the commutation bus voltage and the reference voltage if the DC system is in an overvoltage state;

[0033] The reactive power distribution unit is used to calculate the maximum reactive absorption power of each wind turbine generator set and distribute the reactive absorption reference power of each wind turbine generator set according to the proportion of the reactive capacity of the wind turbine generator set to the total reactive capacity of the wind farm;

[0034] The residual reactive power calculation unit is configured to calculate the residual reactive power in the reactive power to be absorbed when the reactive absorption reference power of any wind turbine generator set reaches its maximum reactive absorption power;

[0035] The SVG control unit is used to start the static VAR generator SVG and control the SVG to output the excess reactive power.

[0036] The present invention further provides a readable storage medium storing a computer program, wherein when the computer program is executed by a processor, the processor executes the following steps:

[0037] When a DC commutation failure fault occurs in the wind farm DC system, determining whether the DC commutation failure fault is in an overvoltage state according to the commutation bus voltage;

[0038] If the wind farm DC system is in an overvoltage state, calculating the reactive power that the wind farm DC system needs to absorb according to the deviation between the commutation bus voltage and the reference voltage;

[0039] Calculating the maximum reactive absorption power of each wind turbine in the wind farm DC system, allocating the reactive power required to be absorbed to each wind turbine according to the ratio of the reactive capacity of the wind turbine to the total reactive capacity of the wind farm, and obtaining a reactive absorption reference power for each wind turbine;

[0040] When the reactive absorption reference power of any wind turbine generator set reaches the maximum reactive absorption power, the remaining reactive power in the reactive power to be absorbed is determined;

[0041] The static VAR generator SVG is turned on, and the static VAR generator SVG outputs the remaining reactive power.

[0042] The present invention further provides a computer device, comprising a memory and a processor, wherein the memory stores a computer program, and the processor executes the following steps:

[0043] When a DC commutation failure fault occurs in the wind farm DC system, determining whether the DC commutation failure fault is in an overvoltage state according to the commutation bus voltage;

[0044] If the wind farm DC system is in an overvoltage state, calculating the reactive power that the wind farm DC system needs to absorb according to the deviation between the commutation bus voltage and the reference voltage;

[0045] Calculating the maximum reactive absorption power of each wind turbine in the wind farm DC system, allocating the reactive power required to be absorbed to each wind turbine according to the ratio of the reactive capacity of the wind turbine to the total reactive capacity of the wind farm, and obtaining a reactive absorption reference power for each wind turbine;

[0046] When the reactive absorption reference power of any wind turbine generator set reaches the maximum reactive absorption power, the remaining reactive power in the reactive power to be absorbed is determined;

[0047] The static VAR generator SVG is turned on, and the static VAR generator SVG outputs the remaining reactive power.

[0048] The adoption of the embodiments of the present invention has the following beneficial effects: the present invention dynamically calculates the reactive power that the system needs to absorb based on the deviation between the commutation bus voltage and the reference voltage, so that the reactive regulation amount is directly linked to the voltage deviation, thereby improving the targeted response; secondly, power is distributed according to the reactive capacity ratio of the wind turbine group, ensuring that multiple wind turbines share the reactive task according to their actual capacity, avoiding overload of a single device; when the wind turbine reaches its maximum absorption capacity, the SVG is triggered to take over the remaining reactive power, forming a collaborative mode of "wind turbine control + static VAR generator control", avoiding voltage oscillations that may be caused by traditional independent control, and realizing precise suppression of overvoltage in the wind farm DC system through the hierarchical collaborative control mechanism, significantly enhancing the transient stability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0050] in:

[0051] Figure 1 Schematic diagram of a flow chart of a coordinated voltage control method in one embodiment. DETAILED DESCRIPTION

[0052] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments; for the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0053] In the following description, numerous specific details are given to provide a more thorough understanding of the present invention; however, it will be apparent to those skilled in the art that the present invention may be practiced without one or more of these details; in other examples, some technical features known in the art are not described to avoid confusion with the present invention, and it should be understood that the present invention may be practiced in different forms and should not be construed as limited to the embodiments set forth herein; on the contrary, these embodiments are provided to make the disclosure thorough and complete and to fully convey the scope of the present invention to those skilled in the art.

[0054] The terminology used herein is intended only to describe specific embodiments and is not intended to limit the present invention. When used herein, the singular forms "a," "an," and "the" are intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "comprising" and / or "including," when used in this specification, identify the presence of the recited features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0055] In order to thoroughly understand the present invention, a detailed structure will be presented in the following description to illustrate the technical solution proposed by the present invention; optional embodiments of the present invention are described in detail below, but in addition to these detailed descriptions, the present invention may also have other implementation methods.

[0056] like Figure 1 As shown, in one embodiment, a coordinated voltage control method is provided. The method is applied to a DC system of a wind farm, where the wind farm includes a plurality of wind turbines. The method includes steps S101 to S105, which are described in detail as follows:

[0057] S101. When a DC commutation failure fault occurs in the DC system of the wind farm, determining whether the DC commutation failure fault is in an overvoltage state according to the commutation bus voltage;

[0058] By monitoring the converter bus voltage, the fault type (whether accompanied by overvoltage) can be judged in the first time. There are many reasons for overvoltage fault: DC blocking fault, DC commutation failure fault, and nearby AC fault. Different overvoltage types have different coping strategies, and this step can provide key decision basis for subsequent control strategies.

[0059] In some embodiments, when the converter bus voltage of the wind farm DC system presents a three-phase symmetric characteristic, the amplitude of the converter bus voltage is greater than a preset lower threshold of voltage amplitude, and the absolute value of the rate of change of the converter bus voltage is within a fixed range, it is determined that the DC system has a DC commutation failure fault.

[0060] Preferably, if the DC system does not have a DC commutation failure fault, the wind turbine keeps the active power output, and the reactive power output value is 0; the static var generator SVG determines the voltage of the DC system by outputting a constant voltage.

[0061] In some embodiments, determining whether the DC commutation failure fault is in an overvoltage state according to the converter bus voltage specifically includes: when the converter bus voltage is greater than a threshold voltage, it is determined that it is in an overvoltage state.

[0062] In fact, when the wind farm DC system is in normal operation, no commutation failure signal is detected (SCFI=0), at this time, the control strategy is that the grid-side converter keeps unit power factor output (i.e. full active power output, and reactive power is 0). The control signal Swind=0 indicates that the wind turbine is in a normal power generation mode, thereby realizing maximum active power grid connection and ensuring energy conversion efficiency.

[0063] When the wind farm DC system has a commutation failure fault, the commutation failure signal (SCFI=1) and when the converter bus voltage is less than or equal to a threshold voltage (low voltage scenario), the control strategy is that the wind turbine unit keeps the original operation mode, and no low voltage ride through (LVRT) action is triggered, avoiding the delay of the required reactive power injection operation of low voltage ride through, which may exacerbate the transient overvoltage (such as misjudgment superimposed with overvoltage scenario), and improving the stability of the transient process.

[0064] When the wind farm DC system has a commutation failure fault, the commutation failure signal (SCFI=1) and when the converter bus voltage is greater than a threshold voltage (overvoltage scenario), the wind turbine adjusts the reactive power reference value (the reactive power required to be absorbed by the wind farm DC system) according to the real-time value of the bus voltage and the grid point power characteristics, absorbs reactive power to suppress overvoltage, and allocates reactive power tasks in proportion, thereby quickly responding to the overvoltage demand and reducing the bus voltage by using the reactive power regulation capability of the wind turbine converter.

[0065] S102, if the wind farm DC system is in an overvoltage state, calculating the reactive power required to be absorbed by the wind farm DC system according to the deviation of the commutation bus voltage from the reference voltage;

[0066] In some embodiments, the reactive power that needs to be absorbed by the wind farm DC system is calculated based on the deviation between the commutation bus voltage and the reference voltage, specifically including:

[0067] Calculate the reactive power Q that the DC system needs to absorb according to the following formula: demand :

[0068] Q demand =K·(U p -U ref )

[0069] Where U p is the commutation bus voltage; U ref is the reference voltage; K is the proportional coefficient.

[0070] Converting voltage deviations into specific reactive power requirements (the amount of reactive power to be absorbed) provides a clear mathematical basis for control strategies and facilitates subsequent power allocation. Reactive power absorption offsets overvoltage energy, leveraging the power system's "reactive power-voltage" coupling (excess reactive power causes voltage to rise, while reactive power absorption reduces voltage), directly impacting the essential link in voltage regulation.

[0071] In some embodiments, the maximum reactive absorption power of each wind turbine generator set in the wind farm DC system is the absolute value of the maximum active power of a single wind turbine generator set or the minimum reactive power of a single wind turbine generator set.

[0072] In some embodiments, the maximum active power of a single wind turbine is determined based on the maximum allowable current of the single wind turbine and the real-time voltage of the grid connection point of the single wind turbine:

[0073] P gmax =3U g I gmax

[0074] Where, P gmax is the maximum active power of a single wind turbine; U g is the real-time voltage peak value of a single wind turbine grid connection point; I gmax It is the maximum allowable current of a single wind turbine.

[0075] In some embodiments, the minimum reactive power of a single wind turbine is determined based on the current active power of the wind turbine, the real-time voltage at the wind turbine grid connection point, and the maximum allowable current of the wind turbine:

[0076]

[0077] Where Q gmin is the minimum reactive power of a single wind turbine, P g is the current active power of a single wind turbine; m is the modulation coefficient; Ug is the real-time voltage of the wind turbine grid connection point; ω s is the synchronous electrical angular velocity; L g I is the inductance of the wind turbine line; gmax It is the maximum allowable current of a single wind turbine.

[0078] S103, calculating the maximum reactive absorption power of each wind turbine in the wind farm DC system, allocating the reactive power required to be absorbed to each wind turbine according to the ratio of the reactive capacity of the wind turbine to the total reactive capacity of the wind farm, and obtaining a reactive absorption reference power for each wind turbine;

[0079] Distributing the total reactive power demand across wind turbines prevents overloading of individual units, fully utilizing the wind farm's overall reactive power regulation capabilities, and improving system redundancy. Allocating tasks based on reactive power capacity ensures that each unit operates within its capabilities, meeting control accuracy requirements while optimizing resource utilization (for example, preventing small-capacity units from shouldering excessive loads). Setting a clear reference power for each unit facilitates closed-loop control of the wind turbine's converter (such as a power electronic converter) and ensures consistent dynamic reactive power regulation.

[0080] In some embodiments, the reactive power required to be absorbed is allocated to each wind turbine according to the ratio of the reactive capacity of the wind turbine to the total reactive capacity of the wind farm, so as to obtain the reactive absorption reference power of each wind turbine, which specifically includes:

[0081] According to the minimum reactive power Q of a single wind turbine gmin and the maximum active power of a single wind turbine P gmax Determine the total reactive capacity Q of the wind farm wmax :

[0082]

[0083] Where Q wmax is the total reactive capacity of the wind farm; n is the number of wind turbines in the wind farm; P gmax is the maximum active power of a single unit; P g is the current active power of a single unit; Q gmin is the minimum reactive power of a single unit;

[0084] According to the converter capacity S of a single wind turbine g Total capacity of wind turbine converter S w The ratio of each wind turbine is used to obtain the reactive absorption reference power Q ref_wind :

[0085]

[0086] Where S gis the converter capacity of a single wind turbine; S w is the total capacity of the wind farm unit converter; Q wmax is the total reactive capacity of the wind farm; Q gmin It is the minimum reactive power of a single unit.

[0087] Specifically, suppose a wind farm has n=10 units, and the P of a single unit is gmax =2MW, current active power P g =1.5MW, the minimum reactive power of a single unit Q gmin =-0.8Mvar (must absorb 0.8Mvar reactive power):

[0088] Maximum reactive capacity of a single unit:

[0089] Available reactive capacity of a single unit: Q g_available =1.32-(-0.8)=2.12Mvar

[0090] Total reactive capacity of wind farm: Q wmax =10×2.12=21.2Mvar

[0091] It can be seen that under the current working conditions, the wind farm can cooperate with the static VAR generator SVG to absorb a maximum of 21.2M var Reactive power to suppress overvoltage.

[0092] S104. When the reactive absorption reference power of any wind turbine generator set reaches the maximum reactive absorption power, determining the remaining reactive power in the reactive power to be absorbed;

[0093] Real-time monitoring of wind turbine reactive absorption reference power close to output limits prevents converter damage or grid disconnection due to overload of individual turbines, ensuring equipment safety. Furthermore, residual reactive power calculations identify demand exceeding wind turbine capacity, providing a transition interface for coordinated control of static VAR generators (SVGs).

[0094] S105 : Turn on the static VAR generator SVG to output the remaining reactive power.

[0095] As a dedicated reactive power compensation device, the static VAR generator (SVG) boasts fast response and a wide regulation range. It can quickly absorb excess reactive power that wind turbines cannot absorb, thus offsetting the upper limit of the turbine's regulation capacity. The hierarchical control mode of wind turbines and SVGs reduces unnecessary SVG investment while ensuring uninterrupted reactive power regulation in extreme situations (such as overload of a large number of turbines), shortening the duration of overvoltages. Hybrid regulation reduces the risk of reliance on a single device, forms a multi-tiered reactive power support system, and improves the transient stability of wind farms under complex fault conditions.

[0096] Wind turbines are a larger source of reactive power than devices like static VAR generators (SVGs). The wind farm's dynamic reactive compensation SVG works in conjunction with the wind turbines. The basic voltage regulation principle is to reduce the reactive power increase during transient voltage rises caused by commutation failures. During commutation failure low voltage periods, the SVG's reactive output reference value is set to 0. During commutation failure overvoltage periods, when the wind turbines exceed the controllable allowable range, the SVG is activated to absorb excess reactive power, improving the wind farm's high voltage ride-through capability. After the transient period ends, the control mode is readjusted.

[0097] Specifically, when the wind farm DC system detects no commutation failure signal (SCFI = 0), the static VAR generator (SVG) control parameter Sbreak = 0, indicating that the SVG is in constant voltage control mode, maintaining the bus voltage near the rated value (e.g., ±5%). Dynamically adjusting reactive output (inductive or capacitive) compensates for system reactive fluctuations and maintains voltage stability.

[0098] When the wind farm DC system detects a commutation failure signal (SCFI = 1), the system enters a fault transient process. Scenario 1: The commutation bus voltage ≤ the threshold voltage, and the static VAR generator (SVG) reactive output is set to 0 (i.e., shut down). This prevents reactive injection caused by the SVG's delayed response (typically 10 to 20 ms) from superimposing on system overvoltage and worsening the transient process.

[0099] Scenario 2: The commutation bus voltage is greater than the threshold voltage, indicating an overvoltage state. In this case, the control strategy is for the static VAR generator (SVG) to work with the wind turbines to absorb excess reactive power: the total reactive power required by the wind farm DC system is calculated, and the wind turbines take priority in reactive power absorption (allocated according to their capacity ratio, as described above). When the absorption capacity of a single wind turbine reaches its corresponding upper limit, the static VAR generator (SVG) automatically supplements the remaining reactive power demand: Q SVG＝ Q total -Q 风机 , thus forming a hierarchical reactive power control system with "wind turbines as the main and SVG as the auxiliary", improving the overvoltage suppression efficiency.

[0100] When the wind farm DC system detects a commutation failure end signal (SCFI = 0), the wind farm DC system enters the recovery phase. At this point, the control strategy switches back to constant voltage control mode, gradually reducing the SVG's reactive power absorption to avoid voltage sags. This prevents secondary voltage fluctuations caused by sudden changes in the control mode, achieving a soft landing of the system after a fault.

[0101] In summary, the present invention achieves effective coordinated control of wind turbines and SVGs during faults, enabling them to share more surplus reactive power from the sending-end system, optimizing reactive power response characteristics, improving overvoltage conditions at new energy stations, and effectively suppressing transient overvoltages in the sending-end AC system under DC commutation failures. This avoids the overvoltage-increasing effect of reactive current withdrawal delays, thereby ensuring the safe and stable operation of the power grid and related equipment.

[0102] The present invention also proposes a coordinated control system for voltage, which includes: a fault judgment unit, a reactive power demand calculation unit, a reactive power distribution unit, a residual reactive power calculation unit and an SVG control unit;

[0103] A fault judgment unit is used to judge whether the fault is in an overvoltage state based on the commutation bus voltage when a DC commutation failure fault is detected in the DC system of the wind farm;

[0104] A reactive power demand calculation unit is used to calculate the reactive power that the DC system needs to absorb based on the deviation between the commutation bus voltage and the reference voltage if the DC system is in an overvoltage state;

[0105] The reactive power distribution unit is used to calculate the maximum reactive power absorbed by each wind turbine and allocate the reactive power absorption reference power to each wind turbine according to the proportion of the reactive capacity of the wind turbine to the total reactive capacity of the wind farm;

[0106] The residual reactive power calculation unit is used to calculate the residual reactive power in the reactive power to be absorbed when the reactive absorption reference power of any wind turbine generator set reaches its maximum reactive absorption power;

[0107] The SVG control unit is used to start the static VAR generator SVG and control the SVG to output surplus reactive power.

[0108] The present invention further provides a readable storage medium storing a computer program. When the computer program is executed by a processor, the processor performs the following steps:

[0109] When a DC commutation failure occurs in the DC system of a wind farm, it is determined whether the DC commutation failure is in an overvoltage state based on the commutation bus voltage;

[0110] If the wind farm DC system is in an overvoltage state, the reactive power required to be absorbed by the wind farm DC system is calculated according to the deviation of the commutation bus voltage from the reference voltage;

[0111] The maximum reactive power absorption of each wind turbine in the wind farm DC system is calculated, the reactive power required to be absorbed is allocated to each wind turbine according to the proportion of the reactive capacity of the wind turbine in the total reactive capacity of the wind farm, and the reactive power absorption reference power of each wind turbine is obtained;

[0112] When the reactive power absorption reference power of any one wind turbine reaches the maximum reactive power absorption, the remaining reactive power in the reactive power required to be absorbed is determined;

[0113] The static var generator SVG is started, and the remaining reactive power is output through the static var generator SVG.

[0114] The application further provides a computer device comprising a memory and a processor, the memory stores a computer program, and the computer program is executed by the processor to perform the following steps:

[0115] When the wind farm DC system occurs a DC commutation failure fault, whether the DC commutation failure fault is in an overvoltage state is determined according to the commutation bus voltage;

[0116] If the wind farm DC system is in an overvoltage state, the reactive power required to be absorbed by the wind farm DC system is calculated according to the deviation of the commutation bus voltage from the reference voltage;

[0117] The maximum reactive power absorption of each wind turbine in the wind farm DC system is calculated, the reactive power required to be absorbed is allocated to each wind turbine according to the proportion of the reactive capacity of the wind turbine in the total reactive capacity of the wind farm, and the reactive power absorption reference power of each wind turbine is obtained;

[0118] When the reactive power absorption reference power of any one wind turbine reaches the maximum reactive power absorption, the remaining reactive power in the reactive power required to be absorbed is determined;

[0119] The static var generator SVG is started, and the remaining reactive power is output through the static var generator SVG.

[0120] Those skilled in the art will understand that all or part of the processes in the above-mentioned embodiment methods can be implemented by instructing the relevant hardware through a computer program. The program can be stored in a non-volatile computer-readable storage medium. When the program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided in this application may include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).

[0121] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0122] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person skilled in the art would be able to make numerous modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. The above disclosures are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A coordinated voltage control method for a DC system of a wind farm, wherein the wind farm comprises a plurality of wind turbines, characterized in that: The method comprises: When a DC commutation failure fault occurs in the wind farm DC system, determining whether the DC commutation failure fault is in an overvoltage state according to the commutation bus voltage; If the wind farm DC system is in an overvoltage state, calculating the reactive power that the wind farm DC system needs to absorb according to the deviation between the commutation bus voltage and the reference voltage; Calculating the maximum reactive absorption power of each wind turbine in the wind farm DC system, allocating the reactive power required to be absorbed to each wind turbine according to the ratio of the reactive capacity of the wind turbine to the total reactive capacity of the wind farm, and obtaining a reactive absorption reference power for each wind turbine; When the reactive absorption reference power of any wind turbine generator set reaches the maximum reactive absorption power, the remaining reactive power in the reactive power to be absorbed is determined; The static VAR generator SVG is turned on, and the static VAR generator SVG outputs the remaining reactive power.

2. The coordinated voltage control method according to claim 1, characterized in that: When the commutation bus voltage of the wind farm DC system presents a three-phase symmetrical characteristic, the commutation bus voltage amplitude is greater than a preset voltage amplitude lower limit threshold, and the absolute value of the commutation bus voltage change rate is within a fixed range, it is determined that a DC commutation failure fault occurs in the DC system.

3. The coordinated voltage control method according to claim 1, characterized in that: The step of calculating the reactive power that the wind farm DC system needs to absorb based on the deviation between the commutation bus voltage and the reference voltage specifically includes: Calculate the reactive power Q that the DC system needs to absorb according to the following formula: demand : Q demand =K·(U p -U ref ) Where U p is the commutation bus voltage; U ref is the reference voltage; K is the proportional coefficient.

4. The coordinated voltage control method according to claim 1, characterized in that: The maximum reactive absorption power of each wind turbine generator set in the wind farm DC system is the absolute value of the maximum active power of a single wind turbine generator set or the minimum reactive power of a single wind turbine generator set.

5. The coordinated voltage control method according to claim 4, characterized in that: The maximum active power of a single wind turbine is determined based on the maximum allowable current of the single wind turbine and the real-time voltage at the grid connection point of the single wind turbine: P gmax =3U g ·I gmax Where, P gmax is the maximum active power of a single wind turbine; U g is the real-time voltage peak value of a single wind turbine grid connection point; I gmax It is the maximum allowable current of a single wind turbine.

6. The coordinated voltage control method according to claim 4, characterized in that: The minimum reactive power of a single wind turbine is determined based on the current active power of the wind turbine, the real-time voltage at the wind turbine grid connection point, and the maximum allowable current of the wind turbine: Where Q gmin is the minimum reactive power of a single wind turbine, P g is the current active power of a single wind turbine; m is the modulation coefficient; U g is the real-time voltage of the wind turbine grid connection point; ω s is the synchronous electrical angular velocity; L g I is the inductance of the wind turbine line; gmax It is the maximum allowable current of a single wind turbine.

7. The coordinated voltage control method according to claim 1, characterized in that: The step of allocating reactive power required to be absorbed to each wind turbine generator set according to the ratio of the reactive capacity of the wind turbine generator set to the total reactive capacity of the wind farm to obtain a reactive absorption reference power of each wind turbine generator set specifically includes: According to the minimum reactive power Q of a single wind turbine gmin and the maximum active power of a single wind turbine P gmax Determine the total reactive capacity Q of the wind farm wmax : Where Q wmax is the total reactive capacity of the wind farm; n is the number of wind turbines in the wind farm; P gmax is the maximum active power of a single unit; P g is the current active power of a single unit; Q gmin is the minimum reactive power of a single unit; According to the converter capacity S of a single wind turbine g Accounting for the total capacity S of the wind turbine converter w The ratio of each wind turbine is used to obtain the reactive absorption reference power Q ref_wind : Where S g is the converter capacity of a single wind turbine; S w is the total capacity of the wind farm unit converter; Q wmax is the total reactive capacity of the wind farm; Q gmin It is the minimum reactive power of a single unit.

8. A coordinated control system for voltage, characterized in that: The system includes: a fault judgment unit, a reactive power demand calculation unit, a reactive power distribution unit, a residual reactive power calculation unit and an SVG control unit; The fault judgment unit is configured to, when a DC commutation failure fault is detected in the wind farm DC system, judge whether the fault is in an overvoltage state based on the commutation bus voltage; The reactive power demand calculation unit is configured to calculate the reactive power that the DC system needs to absorb based on the deviation between the commutation bus voltage and the reference voltage if the DC system is in an overvoltage state; The reactive power distribution unit is used to calculate the maximum reactive absorption power of each wind turbine generator set and distribute the reactive absorption reference power of each wind turbine generator set according to the proportion of the reactive capacity of the wind turbine generator set to the total reactive capacity of the wind farm; The residual reactive power calculation unit is configured to calculate the residual reactive power in the reactive power to be absorbed when the reactive absorption reference power of any wind turbine generator set reaches its maximum reactive absorption power; The SVG control unit is used to start the static VAR generator SVG and control the SVG to output the excess reactive power.

9. A readable storage medium storing a computer program, wherein when the computer program is executed by a processor, the processor is caused to perform the steps of the method according to any one of claims 1 to 7.

10. A computer device comprising a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor is caused to perform the steps of the method according to any one of claims 1 to 7.

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