A direct current voltage control method and system for a grid-connection type direct-drive wind turbine grid-connection system

Abstract

The application relates to a direct-current voltage control method and system of a grid-connection type direct-drive wind turbine grid-connection system, the method comprising the following steps: setting an energy temporary storage control unit in the grid-connection type direct-drive wind turbine grid-connection system; when a grid-side fault occurs in the grid-connection type direct-drive wind turbine grid-connection system, calculating a direct-current voltage correction value based on the difference between the angular velocity output by a virtual synchronous motor control unit of a grid-side converter and the rated angular velocity of the grid-side; adding a preset original direct-current voltage reference value and the direct-current voltage correction value to obtain a real-time direct-current voltage reference value of the grid-side of the grid-connection type direct-drive wind turbine grid-connection system; and controlling the direct-drive wind turbine direct-current link to actively store the transient imbalance power between the wind turbine and the grid-connection power during the transient period based on the corrected direct-current voltage reference value, so as to solve the grid-side synchronous stability problem caused by power imbalance when the offshore wind turbine is in a transient fault of the grid.

Description

TECHNICAL FIELD

[0001] The application relates to a direct-current voltage control method and system for a grid-connection type direct-drive wind turbine grid-connection system and belongs to the technical field of power grid fault processing. BACKGROUND

[0002] To solve the problems of low inertia and the like under normal operation conditions of an existing power grid, a grid-connection type direct-drive wind turbine is gradually promoted and applied in an offshore wind power system as a control mode capable of providing inertia and voltage support.

[0003] However, when a short-circuit fault or a phase jump fault occurs in the power grid, the grid-side converter of the grid-connection type direct-drive wind turbine may face the risk of transient instability, thereby further causing large-scale offshore wind turbines to be disconnected from the grid and endangering the stable operation of the power system.

[0004] At present, the control method for improving the transient stability of the grid-connection type direct-drive wind turbine mainly focuses on the grid side, for example, adjusting the virtual inertia and damping of the grid-side converter in the transient process, but these control methods added on the alternating current side often ignore the dynamic characteristics of the direct-current link of the direct-drive wind turbine back-to-back converter.

[0005] Therefore, the control method considering the direct-current link voltage stability of the direct-drive wind turbine system and the alternating current side synchronous stability needs to be proposed. SUMMARY

[0006] In order to solve the problems in the prior art, the application provides a direct-current voltage control method and system for a grid-connection type direct-drive wind turbine grid-connection system.

[0007] The technical scheme of the application is as follows:

[0008] In one aspect, the application provides a direct-current voltage control method for a grid-connection type direct-drive wind turbine grid-connection system, comprising the following steps:

[0009] An energy temporary storage control unit is arranged in the grid-connection type direct-drive wind turbine grid-connection system, and when a fault occurs in the grid-side of the grid-connection type direct-drive wind turbine grid-connection system, the energy temporary storage control unit calculates a direct-current voltage correction value based on the difference between the angular velocity output by the virtual synchronous motor control unit of the grid-side converter and the rated angular velocity of the grid-side.

[0010] The preset original direct-current voltage reference value and the direct-current voltage correction value are added to obtain the real-time direct-current voltage reference value of the grid-side of the grid-connection type direct-drive wind turbine grid-connection system.

[0011] Preferably, the fault occurring in the grid-side of the grid-connection type direct-drive wind turbine includes an over-limit power angle fault and an over-limit voltage fault.

[0012] Preferably, the specific judgment steps of the grid-side power angle out-of-limit fault of the grid-connected direct-driven wind turbine are as follows:

[0013] The real-time power angle value of the grid-side converter grid-connected point of the grid-connected direct-driven wind turbine grid-connected system is collected;

[0014] The difference between the real-time power angle value of the grid-side converter grid-connected point of the grid-connected direct-driven wind turbine grid-connected system and the preset power angle initial value is calculated;

[0015] The difference between the real-time power angle value and the preset power angle initial value is compared with the preset power angle threshold value, and if it is greater than the preset power angle threshold value, it is judged that the grid-side of the grid-connected direct-driven wind turbine has a power angle out-of-limit fault.

[0016] Preferably, the specific judgment steps of the grid-side voltage out-of-limit fault of the grid-connected direct-driven wind turbine are as follows:

[0017] The real-time voltage amplitude of the grid-side converter grid-connected point of the grid-connected direct-driven wind turbine grid-connected system is collected;

[0018] The difference between the real-time voltage amplitude of the grid-side converter grid-connected point of the grid-connected direct-driven wind turbine grid-connected system and the voltage rated value is calculated;

[0019] The difference between the real-time voltage amplitude and the voltage rated value is compared with the preset voltage threshold value, and if it is greater than the preset voltage threshold value, it is judged that the grid-side of the grid-connected direct-driven wind turbine has a voltage out-of-limit fault.

[0020] Preferably, the calculation steps of the DC voltage correction value are as follows:

[0021] The difference between the angular velocity output by the virtual synchronous motor control unit of the grid-side converter and the rated angular velocity of the grid-side is respectively passed through a proportional link and a differential link by the energy temporary storage control unit, to obtain a DC voltage proportional correction component and a DC voltage differential correction component;

[0022] The DC voltage proportional correction component and the DC voltage differential correction component are added to obtain a DC voltage correction value.

[0023] Preferably, the DC voltage reference value is taken as the input of the DC voltage outer loop control of the grid-connected direct-driven wind turbine grid-connected system, and after the DC voltage control, the active reference power of the grid-connected direct-driven wind turbine in the fault state is generated. The active reference power is passed through the virtual synchronous control to generate the phase angle of the grid-connected point voltage in the fault state. At this time, the active frequency control equation of the grid-connected direct-driven wind turbine grid-connected system is as follows:

[0024]

[0025]

[0026] Wherein: represents the equivalent virtual inertia of the grid-side converter during the fault period of the grid-connected type direct-driven wind turbine grid-connected system; represents the integral variable; represents the virtual inertia of the grid-side converter under normal conditions of the grid-connected type direct-driven wind turbine grid-connected system; represents the equivalent virtual damping of the grid-side converter during the fault period of the grid-connected type direct-driven wind turbine grid-connected system; represents the virtual damping of the grid-side converter under normal conditions of the grid-connected type direct-driven wind turbine grid-connected system; represents the angular frequency of the grid-connected point during the fault period of the grid-connected type direct-driven wind turbine grid-connected system; represents the equivalent mechanical power; represents the output active power of the grid-side converter during the fault period of the grid-connected type direct-driven wind turbine grid-connected system; represents the proportional gain of the DC voltage control unit of the grid-connected type direct-driven wind turbine grid-connected system; represents the integral gain of the DC voltage control unit of the grid-connected type direct-driven wind turbine grid-connected system; represents the differential gain of the energy storage control unit of the grid-connected type direct-driven wind turbine grid-connected system; represents the proportional gain of the energy storage control unit of the grid-connected type direct-driven wind turbine grid-connected system; represents the power angle value of the grid-connected point at the beginning of the fault period of the grid-connected type direct-driven wind turbine grid-connected system; represents the real-time power angle value of the grid-connected point during the fault period of the grid-connected type direct-driven wind turbine grid-connected system.

[0027] In another aspect, the present application also provides a DC voltage control system of a grid-connected type direct-driven wind turbine grid-connected system, specifically comprising:

[0028] A data acquisition module is configured to acquire the real-time power angle value and the real-time voltage amplitude of the grid-side converter grid-connected point of the grid-connected type direct-driven wind turbine grid-connected system;

[0029] A fault detection signal module is configured to determine whether the grid-side of the grid-connected type direct-driven wind turbine grid-connected system is faulty according to the real-time power angle value and the real-time voltage amplitude of the grid-side converter grid-connected point of the grid-connected type direct-driven wind turbine grid-connected system;

[0030] A DC voltage reference value calculation module is configured to calculate a DC voltage correction value based on the difference between the angular velocity output by the virtual synchronous motor control unit of the grid-side converter and the rated angular velocity of the grid-side by the energy storage control unit, and obtain the real-time DC voltage reference value of the grid-side of the grid-connected type direct-driven wind turbine grid-connected system by adding the preset original DC voltage reference value and the DC voltage correction value.

[0031] In still another aspect, the present application also provides an electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the method according to the present application when executing the program.

[0032] In still another aspect, the present application also provides a computer readable storage medium having a computer program stored thereon, wherein the program, when executed by a processor, implements the method according to the present application.

[0033] The present application has the following advantages:

[0034] 1、The control of the present application, compared with the conventional network configuration type transient enhancement control, does not need to rely on the calculation of time-varying information such as voltage drop depth and line impedance, but only relies on the power angle and its derivative in the grid-side converter synchronous module of the network configuration type direct-driven wind turbine and the voltage amplitude as feedback to judge the fault state of the network configuration type wind turbine converter; the control can not only avoid the transient synchronous instability of the network configuration type wind turbine during the fault period, but also reduce the risk of overvoltage of the DC bus, and does not affect the operation of the wind turbine at the MPPT point; after the introduction of the DC side energy temporary storage control loop, not only can the unbalanced power between the machine side and the grid side be actively stored according to the grid-side attack angle swing during the fault period, but also additional damping dissipation and inertia are added to the system, the increase of inertia is beneficial to reduce the attack angle swing during the transient period and reduce the overshoot of the DC voltage, and the increase of damping is beneficial to the energy dissipation of the unbalanced power during the transient period; the control simultaneously solves the problems of transient synchronous instability of the network configuration type wind turbine and the risk of transient overvoltage of the DC bus.

[0035] 2、When the power grid fault occurs, the present application calculates the DC voltage correction value based on the difference between the angular velocity output by the virtual synchronous motor control unit of the grid-side converter and the rated angular velocity of the grid-side, corrects the DC voltage reference value through the DC voltage correction value, and controls the direct-driven wind turbine DC link to actively store the transient unbalanced power between the wind turbine and the grid-connected power during the transient period based on the corrected DC voltage reference value, thereby solving the problem of grid-side synchronous stability caused by power imbalance when the offshore wind turbine is in transient fault.

[0036] 3、The control structure is simple, parameter adjustment is easy, does not affect the maximum power point tracking operation of the grid-connected type direct-driven wind turbine in the normal operation state of the power grid, can self-adaptively control the DC port of the grid-side converter of the grid-connected type direct-driven wind turbine system to temporarily store the unbalanced energy existing in the back-to-back converter at the moment of the transient fault of the power grid, provide instant transient stability support for the grid-side converter, shorten the transient process of the system under the condition of the transient fault of the power grid, make the system restore the stable operation state in a short time, and the wind turbine can still operate near the MPPT point during the fault period, and the overshoot of the DC capacitor voltage is reduced, the overvoltage risk of the DC port is alleviated, in addition, the control only uses the power angle and its derivative and the voltage amplitude in the synchronous module of the grid-side converter of the grid-connected type direct-driven wind turbine as feedback, does not depend on time-varying system information such as voltage drop degree and line impedance, avoids the deviation of the temporarily stored energy of the DC port caused by communication delay, improves the rapidity of the transient stability support, and reduces the complexity and implementation difficulty of the control strategy. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 It is a typical topology structure diagram of the grid-connected type direct-driven wind turbine grid-connected system.

[0038] Figure 2 It is a control block diagram of the machine-side converter of the grid-connected type direct-driven wind turbine grid-connected system.

[0039] Figure 3 It is a control block diagram of the grid-side converter of the grid-connected type direct-driven wind turbine grid-connected system.

[0040] Figure 4 It is a DC voltage synchronous control block diagram of the grid-connected type direct-driven wind turbine under the condition of the power grid fault of the embodiment of the application.

[0041] Figure 5 It is a structure diagram of the fault detection signal unit of the embodiment of the application.

[0042] Figure 6 It is an energy temporary storage control unit structure diagram of the embodiment of the application. DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0044] It should be understood that the step numbers used herein are only for the convenience of description, and are not limited to the execution sequence of the steps.

[0045] It should be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0046] The terms “comprising” and “including” indicate the presence of the described feature, whole, step, operation, element and / or component, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0047] The term “and / or” refers to any combination of one or more of the associated listed items, as well as all possible combinations, and includes these combinations.

[0048] See Figure 1 Traditional grid-connected direct-drive wind turbine systems consist of a wind turbine and its control system, a permanent magnet synchronous generator (PMSG), and a back-to-back full-power converter and its control system. The back-to-back full-power converter and its control system consist of a turbine-side converter and its control system, a DC-side capacitor, and a grid-side converter and its control system.

[0049] The machine-side control process of the grid-connected direct-drive wind turbine system is as follows: Figure 2 As shown, the function of the turbine-side converter control is to achieve the maximum output power of the wind turbine, which is then output from the turbine-side converter to the DC port of the grid-side converter. The permanent magnet synchronous generator rotor electric angular velocity... After passing the MPPT control algorithm, a power outer loop power reference is generated. The setpoint for the inner current loop control is generated by the PI controller. , include as well as Finally, after current inner loop control, the reference voltage of the machine-side converter is generated. In addition, the parameters in the figure... Indicates the output power of the machine-side converter; , These represent the d-axis current reference and the q-axis current reference, respectively. , These represent the measured current components of the stator along the d-axis and the measured current components along the q-axis, respectively. Indicates the electrical angle of the rotor of a permanent magnet synchronous generator;

[0050] The grid-side control process of the grid-connected direct-drive wind turbine system is as follows: Figure 3As shown, the grid-side converter controls the power angle characteristics of the simulation synchronous motor while maintaining the balance of the DC side voltage, and the DC voltage Figure 3 is subtracted from the DC reference voltage to obtain the active power correction value after the PI controller , which is added to the machine-side converter output power to generate the virtual synchronous motor active power reference value , and then the grid-side converter angular frequency and phase angle are generated after the damping and inertia of the virtual synchronous motor active power, and the grid-side converter grid point output voltage amplitude is generated by the virtual synchronous motor reactive power. .

[0051] When the grid has a short-circuit fault or phase jump fault, the grid-side converter of the grid-connected type direct-driven wind turbine system may face the risk of transient instability, which further causes large-scale offshore wind turbine generators to be off-grid, endangering the stable operation of the power system. Therefore, the embodiment of the present application proposes a DC voltage control method for a grid-connected type direct-driven wind turbine system, which specifically includes the following steps:

[0052] S100, an energy temporary storage control unit is arranged in the grid-connected type direct-driven wind turbine system, and when the grid-side of the grid-connected type direct-driven wind turbine system fails, the energy temporary storage control unit calculates a DC voltage correction value based on the difference between the angular velocity output by the virtual synchronous motor control unit of the grid-side converter and the rated angular velocity of the grid-side;

[0053] S200, the preset original DC voltage reference value is added to the DC voltage correction value to obtain the real-time DC voltage reference value of the grid-side of the grid-connected type direct-driven wind turbine system.

[0054] In some embodiments, the fault occurring on the grid-side of the grid-connected type direct-driven wind turbine includes an over-limit power angle fault and an over-limit voltage fault.

[0055] In some embodiments, the specific judgment steps of the over-limit power angle fault of the grid-side of the grid-connected type direct-driven wind turbine are as follows:

[0056] S301, the real-time power angle value of the grid-side converter grid point of the grid-connected type direct-driven wind turbine system is collected;

[0057] S302, the difference between the real-time power angle value of the grid-side converter grid point of the grid-connected type direct-driven wind turbine system and the preset power angle initial value is calculated;

[0058] S303. Compare the difference between the real-time power angle value and the preset initial power angle value with the preset power angle threshold. If the difference is greater than the preset power angle threshold, it is determined that a power angle over-limit fault has occurred on the grid side of the grid-type direct-drive wind turbine.

[0059] In some embodiments, the specific steps for determining grid-side voltage over-limit faults in grid-connected direct-drive wind turbines are as follows:

[0060] S401. Collect the real-time voltage amplitude of the grid-side converter connection point of the grid-connected system of the grid-type direct-drive wind turbine;

[0061] S402. Calculate the difference between the real-time voltage amplitude and the rated voltage at the grid connection point of the grid-side converter in a grid-connected system of a grid-type direct-drive wind turbine.

[0062] S403. Compare the difference between the real-time voltage amplitude and the rated voltage with the preset voltage threshold. If it is greater than the preset voltage threshold, it is determined that a voltage over-limit fault has occurred on the grid side of the grid-type direct-drive wind turbine.

[0063] In one specific embodiment, a fault detection signal unit is installed in the grid-connected system of a grid-type direct-drive wind turbine, such as... Figure 5 As shown, the fault detection signal unit collects the output voltage amplitude at the grid connection point of the grid-side converter. and real-time power angle value Calculate the output voltage amplitude at the grid connection point of the converter on the grid side. Its voltage rating The difference (After absolute conversion) and real-time power angle value (After absolute conversion) and the preset initial value of the work angle (In this embodiment, the difference is set to the power angle value corresponding to the grid-side converter grid connection point at the initial time point under stable operating conditions of the grid-connected system of the grid-connected direct-drive wind turbine.) ;

[0064] Preset voltage threshold and power angle threshold Set the comparator to execute step S303 and The comparison is performed, and the comparator is set to execute step S403. and The comparison is performed, and when any comparator is triggered, the fault detection signal unit outputs a fault signal. ;

[0065] The expression for the active power output of the grid-side converter is:

[0066] ;

[0067] in: This indicates the active power output of the grid-side converter; Indicates the mains voltage; Indicates the inductance of the power grid; Indicates the reference electrical angular velocity;

[0068] The above formula shows that when a voltage drop fault occurs, i.e. When a sudden decrease occurs, or a phase jump fault occurs, i.e. Any sudden decrease will lead to a reduction in the output active power of the grid-side converter;

[0069] The specific control equation for the output power angle of the grid-side converter is shown in the following formula:

[0070] ;

[0071] in: This represents the virtual inertia of the grid-side converter; This represents the virtual damping of the grid-side converter;

[0072] As can be seen from the above formula, when the output power of the grid-side converter suddenly decreases, the power angle will increase to the point of exceeding the threshold.

[0073] The expression for the reactive power output of the grid-side converter is:

[0074] ;

[0075] in: This indicates the reactive power output of the grid-side converter;

[0076] As can be seen from the above formula, when a voltage drop fault or a phase jump fault occurs, it will lead to a sudden increase in the reactive power output of the converter.

[0077] The specific output voltage amplitude of the grid-side converter is shown in the following formula:

[0078] ;

[0079] in: This represents the reference value for the reactive power of the virtual synchronous motor. This represents the reactive power droop coefficient of the grid-side converter;

[0080] As can be seen from the above formula, when the reactive power output of the converter suddenly increases, the output voltage amplitude will decrease instantaneously and even exceed the threshold.

[0081] In some embodiments, the calculation steps for the DC voltage correction value are as follows:

[0082] The energy storage control unit obtains a difference between the angular velocity output by the virtual synchronous motor control unit of the grid-side converter and a rated angular velocity of the grid-side through a proportional link and a differential link respectively, to obtain a DC voltage proportional correction component and a DC voltage differential correction component;

[0083] The DC voltage proportional correction component and the DC voltage differential correction component are added to obtain a DC voltage correction value.

[0084] In a specific embodiment, an energy storage control unit is arranged in a grid-connected direct-drive wind turbine system, as shown in the figure, the energy storage control unit receives a difference between an angular velocity output by a virtual synchronous motor control unit of a grid-side converter and a rated angular velocity of the grid-side Figure 6 ; ;

[0085] through a proportional link and a differential link respectively, wherein, the proportional link obtains a grid-connected direct-drive wind turbine system DC link transient energy storage facing virtual damping correction, which actively drives the voltage of the grid-connected direct-drive wind turbine system DC link according to the product of the proportional coefficient; the differential link obtains a grid-connected direct-drive wind turbine system DC link transient energy storage facing virtual inertia correction, which realizes the equivalent transmission of the grid-side inertia to the DC link during the fault by correcting the voltage of the grid-connected direct-drive wind turbine system DC link, and reduces the overshoot of the DC link voltage.

[0086] The grid-connected direct-drive wind turbine system DC link transient energy storage facing virtual damping correction and the grid-connected direct-drive wind turbine system DC link transient energy storage facing equivalent mechanical power correction are added to obtain a DC voltage correction value .

[0087] In a specific embodiment, a preset original DC voltage reference value is added to a DC voltage correction value to obtain a real-time grid-side DC voltage reference value of the grid-connected direct-drive wind turbine system. In order to prevent the DC side voltage from exceeding the limit due to active absorption of unbalanced power during the fault, the preset original DC voltage reference value is added to the DC voltage correction value , and then the real-time DC voltage reference value is generated after passing through a fault period DC voltage reference limiting link to actively raise the DC voltage reference value under the transient fault state while avoiding the DC voltage exceeding the limit.

[0088] The energy storage control unit changes the dynamic characteristics of the direct current port of the grid-connected direct drive wind turbine, so that the direct current port can store and compensate the transient power difference of the converter; the unbalanced power of the converter reduced through the direct current port reduces the power angle overshoot, avoids the potential risk of transient power angle instability of the converter, and limits and protects the direct current link voltage of the direct drive wind turbine.

[0089] In some embodiments, the direct current voltage reference value is taken as the input of the direct current voltage outer loop control of the grid-connected direct drive wind turbine system, and after the direct current voltage control, the active reference power of the grid-connected direct drive wind turbine in the fault state is generated, and the phase angle of the grid point voltage in the fault state is generated through the virtual synchronous control. At this time, the active frequency control equation of the grid-connected direct drive wind turbine system is:

[0090]

[0091]

[0092] Wherein: represents the equivalent virtual inertia of the grid-side converter of the grid-connected direct drive wind turbine system during the fault period; represents the integral variable; represents the virtual inertia of the grid-side converter of the grid-connected direct drive wind turbine system in the normal state; represents the equivalent virtual damping of the grid-side converter of the grid-connected direct drive wind turbine system during the fault period; represents the virtual damping of the grid-side converter of the grid-connected direct drive wind turbine system in the normal state; represents the angular frequency of the grid point during the fault period of the grid-connected direct drive wind turbine system; represents the equivalent mechanical power; represents the output active power of the grid-side converter of the grid-connected direct drive wind turbine system during the fault period; represents the proportional gain of the direct current voltage control unit of the grid-connected direct drive wind turbine system; represents the integral gain of the direct current voltage control unit of the grid-connected direct drive wind turbine system; represents the differential gain of the energy storage control unit of the grid-connected direct drive wind turbine system; represents the proportional gain of the energy storage control unit of the grid-connected direct drive wind turbine system; represents the power angle value of the grid point at the beginning of the fault of the grid-connected direct drive wind turbine system; represents the real-time power angle value of the grid point during the fault period of the grid-connected direct drive wind turbine system.

[0093] In some embodiments, a direct current voltage control system of a grid-connected direct drive wind turbine system is provided, which specifically comprises:

[0094] The data acquisition module is configured to acquire a real-time power angle value and a real-time voltage amplitude of a grid-side converter grid-connected point of the grid-connection type direct-driven wind turbine grid-connected system.

[0095] The fault detection signal module is configured to determine whether the grid-side of the grid-connection type direct-driven wind turbine grid-connected system is faulty according to the real-time power angle value and the real-time voltage amplitude of the grid-side converter grid-connected point of the grid-connection type direct-driven wind turbine grid-connected system.

[0096] The DC voltage reference value calculation module is configured to calculate a DC voltage correction value based on a difference between an angular velocity output by a virtual synchronous motor control unit of the grid-side converter and a rated angular velocity of the grid-side by the energy temporary storage control unit, and obtain a real-time DC voltage reference value of the grid-side of the grid-connection type direct-driven wind turbine grid-connected system by adding the preset original DC voltage reference value and the DC voltage correction value.

[0097] In some embodiments, an electronic device is provided, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor implements the method according to any of the embodiments of the present application when executing the program.

[0098] In some embodiments, a computer readable storage medium is provided, which stores a computer program executable by a processor, and the processor implements the method according to any of the embodiments of the present application when executing the program.

[0099] In the embodiments of the present application, "at least one" means one or more, and "multiple" means two or more. The "and / or" describes the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and / or B, which can represent the cases of A alone, A and B together, and B alone. Wherein A and B can be singular or plural. The character " / " generally represents an "or" relationship between the front and rear associated objects. "At least one of the following" and the like means any combination of these items, including any combination of single or multiple items. For example, at least one of a, b and c can represent: a, b, c, a and b, a and c, b and c, or a and b and c, wherein a, b, and c can be single or multiple.

[0100] Those of ordinary skill in the art can realize that the units and algorithm steps described in the embodiments disclosed herein can be realized by electronic hardware, computer software and a combination of electronic hardware and computer software. Whether the functions are realized in hardware or software mode depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0101] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the system, device and unit described above can refer to the corresponding processes in the foregoing method embodiments, and will not be described here.

[0102] In several embodiments provided in the present application, any function realized in the form of a software function unit and sold or used as an independent product can be stored in a computer-readable storage medium. Based on such understanding, the technical solutions of the present application essentially or the parts of the technical solutions that make contributions to the prior art or the parts of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium, includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present application. The foregoing storage medium includes: a U disk, a mobile hard disk, a read-only memory (Read-Only Memory; hereinafter referred to as: ROM), a random access memory (Random Access Memory; hereinafter referred to as: RAM), a magnetic disk or an optical disk, and various media that can store program codes.

[0103] The above is only an embodiment of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent flow transformation obtained by using the content of the specification and drawings of the present application, or direct or indirect application in other related technical fields, is also included in the patent protection scope of the present application.

Claims

1. A DC voltage control method for a grid-connected direct-drive wind turbine system, characterized in that, Includes the following steps: An energy storage control unit is set up in the grid-connected system of grid-type direct-drive wind turbines. When a fault occurs on the grid side of the grid-connected system, the energy storage control unit calculates the DC voltage correction value based on the difference between the angular velocity output by the virtual synchronous motor control unit of the grid-side converter and the rated angular velocity on the grid side. The energy storage control unit is located between the virtual synchronous motor control unit of the grid-side converter and the DC voltage outer loop. The input terminal of the energy storage control unit is connected to the angular velocity signal output by the virtual synchronous motor control unit of the grid-side converter, and the output terminal of the energy storage control unit is connected to the preset original DC voltage reference value superposition node of the DC voltage outer loop. The real-time DC voltage reference value on the grid side of the grid-connected system of the grid-type direct-drive wind turbine is obtained by adding the preset original DC voltage reference value and the DC voltage correction value. The calculation steps for the DC voltage correction value are as follows: The energy storage control unit takes the difference between the angular velocity output by the virtual synchronous motor control unit of the grid-side converter and the rated angular velocity of the grid side, respectively, and passes them through a proportional element and a differential element to obtain the DC voltage proportional correction component and the DC voltage differential correction component. The DC voltage correction value is obtained by adding the DC voltage proportional correction component and the DC voltage differential correction component. Using the DC voltage reference value as the input to the outer loop control of the DC voltage in the grid-connected system of the grid-connected direct-drive wind turbine, the active power reference of the grid-connected wind turbine under fault conditions is generated after DC voltage control. The active power reference is then used to generate the phase angle of the grid connection point voltage under fault conditions through virtual synchronization control. At this time, the active frequency control equation of the grid-connected system of the grid-connected direct-drive wind turbine is: in: This represents the equivalent virtual inertia of the grid-side converter during a fault in a grid-connected direct-drive wind turbine system. Represents the integral variable; This represents the virtual inertia of the grid-side converter in a grid-connected direct-drive wind turbine system under normal conditions. This represents the equivalent virtual damping of the grid-side converter during a fault in a grid-connected direct-drive wind turbine system. This represents the virtual damping of the grid-side converter in a grid-connected direct-drive wind turbine system under normal conditions. This indicates the angular frequency of the grid connection point during a fault in the grid-connected system of a grid-connected direct-drive wind turbine; Represents equivalent mechanical power; This indicates the output active power of the grid-side converter during a fault in the grid-connected system of a grid-type direct-drive wind turbine. This indicates the proportional gain of the DC voltage control unit in a grid-connected system for grid-connected direct-drive wind turbines. This indicates the integral gain of the DC voltage control unit in a grid-connected system for grid-connected direct-drive wind turbines. The differential gain of the energy storage control unit in a grid-connected direct-drive wind turbine system; This indicates the proportional gain of the energy storage control unit in a grid-connected direct-drive wind turbine system. This indicates the power angle value at the grid connection point when a fault occurs in the grid-connected system of a grid-connected direct-drive wind turbine. This indicates the real-time power angle value at the grid connection point during a fault in the grid-connected system of a grid-connected direct-drive wind turbine; This represents the reference value for the active power of the virtual synchronous motor.

2. A DC voltage control system for a grid-connected direct-drive wind turbine system, characterized in that, To implement the method of claim 1, specifically includes: The data acquisition module is used to acquire the real-time power angle value and real-time voltage amplitude of the grid-side converter connection point of the grid-connected system of the grid-type direct-drive wind turbine. The fault detection signal module is used to determine whether there is a fault on the grid side of the grid-connected system ... The DC voltage reference value calculation module is used to calculate the DC voltage correction value by using the difference between the angular velocity output by the virtual synchronous motor control unit of the grid-side converter and the rated angular velocity of the grid side based on the energy temporary storage control unit. After adding the preset original DC voltage reference value and the DC voltage correction value, the real-time DC voltage reference value of the grid side of the grid-connected direct-drive wind turbine system is obtained.

3. An electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the method as described in claim 1.

4. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the method as described in claim 1.

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