Direct-drive net-forming type wind generating set control system with inertia self-sustaining function

Abstract

The invention discloses a control method for a direct-drive type grid-forming wind generating set with an inertia self-sustaining function, and relates to the technical field of wind generating set control. The method comprises the steps that a grid side or machine side power reference value is adjusted during a fault period; acquiring a control output angular frequency of a grid-side converter, obtaining a virtual power or voltage compensation value for inertia self-sustaining control after the control output angular frequency passes through a first transient stability controller and an amplitude limiter, and feeding back the virtual power or voltage compensation value to a grid-side reference adjustment module; the grid-side virtual compensation value is fed back to a machine-side converter, and a machine-side compensation value for inertia self-sustaining control is obtained after the grid-side virtual compensation value passes through a second transient stability controller and an amplitude limiter; and the angular frequency error output by the grid side synchronization link is converted into a torque compensation current through a third transient stability controller and a torque-current mapping coefficient, and the torque compensation current is fed forward to a machine side reactive current reference. The system inertia can be effectively maintained, the power imbalance of the machine side and the network side is adjusted, and the transient stability and the fault ride-through capability of the system are improved.

Description

Technical Field

[0001] This invention relates to the field of wind turbine generator control technology, specifically a direct-drive grid-type wind turbine generator control system with inertia self-sustaining function. Background Technology

[0002] With the rapid increase in wind power penetration, the inertia of the power system is gradually decreasing, posing a threat to the stable operation of the power system during grid disturbances or faults. Compared with traditional wind turbines, direct-drive grid-connected wind turbines can provide voltage and frequency support, enhance adaptability to weak grids, and are expected to play a key role in future power systems. Grid-connected wind turbines have a certain grid support capability, providing a promising solution for wind power integration into the power system.

[0003] Under grid faults such as voltage dips, the transient stability of grid-connected wind turbines faces severe challenges. In recent years, some scholars have conducted research on reduced-order modeling and transient stability analysis of grid-connected wind turbines. However, most studies only focus on the control dynamics of the grid-side inverter, assuming a constant DC voltage and neglecting the impact of DC voltage control (DVC) on system transient stability. Furthermore, the influence of upstream system dynamics, such as turbine-side dynamics, on grid-side power synchronization and transient stability is often overlooked.

[0004] Currently, few studies focus on the inertia and frequency support capabilities of grid-connected wind turbines. Furthermore, current control optimization for grid-connected wind turbines is limited to simple transient stability enhancement strategies, neglecting power angle instability and DC overvoltage issues caused by power imbalance between the turbine and grid sides. This can easily lead to inverter protection failure and grid disconnection, failing to achieve reliable grid support. To avoid these problems under fault conditions, it is crucial to rationally utilize the energy storage components of grid-connected wind turbines (such as DC-side capacitors and turbine rotors) to improve transient stability and grid support capabilities under fault conditions. Summary of the Invention

[0005] To address the shortcomings mentioned in the background art, the present invention aims to provide a direct-drive grid-connected wind turbine generator control system with inertia self-sustaining function, enabling reliable fault ride-through and power balance during faults; preventing DC voltage over-limit from causing converter disconnection; improving the transient stability of the wind farm; and increasing the equivalent inertia of the system by introducing the actual inertia of the motor on the basis of virtual inertia.

[0006] Firstly, the objective of this invention can be achieved through the following technical solution: a direct-drive grid-connected wind turbine generator control system with inertia self-sustaining function, comprising:

[0007] The grid-side additional control module is used to obtain the angular frequency of the grid-side converter output. After the angular frequency of the grid-side converter output is passed through the first transient stability controller and the limiter, the voltage compensation value for inertia self-sustaining control is output. The voltage compensation value is subtracted from the preset grid-side reference value, and the grid-side compensation reference value of the converter is output to realize the transient grid-side stability enhancement.

[0008] The grid-side compensation reference value of the converter is sent to the machine-side coupling control module, and the angular frequency output by the grid-side converter is sent to the machine-side auxiliary control module.

[0009] The machine-side coupling control module is used to output the machine-side reference compensation value for inertia self-sustaining control after the grid-side compensation reference value of the converter is passed through the second transient stability controller and the limiter. The difference between the machine-side reference compensation value and the preset machine-side reference is calculated, and the machine-side compensation reference value of the converter is output to realize the stability enhancement of the machine side.

[0010] The additional control module on the generator side is used to convert the angular frequency output by the grid-side converter into torque compensation current based on the torque current mapping coefficient through the third transient stability controller. The torque compensation current is then subtracted from the preset generator-side reactive current reference value to output the generator-side reactive current compensation reference value, thus avoiding the deterioration of power imbalance and transient stability of the wind turbine caused by maximum power point tracking (MPPT) control.

[0011] In conjunction with the first aspect, in some implementations of the first aspect, the system further includes: the angular frequency of the grid-side converter output obtained by the grid-side additional control module is processed by the grid-side power control module to obtain the frequency.

[0012] The system also includes a grid-side reference adjustment module and a power synchronization control module.

[0013] In conjunction with the first aspect, in some implementations of the first aspect, the system further includes: the grid-side reference adjustment module is used to adjust the grid-side active power reference value P during a fault. ref The power synchronization control module is used to calculate the angular frequency Δω of the converter output voltage based on the active power and active power reference value of the grid-side converter, and use it as the angular frequency of the grid-side converter output to the grid-side auxiliary control module.

[0014] In conjunction with the first aspect, in some implementations of the first aspect, the system further includes: the adjustment process of the grid-side reference adjustment module includes: under normal operation, the active power reference value P ref Output P controlled by Maximum Power Point Tracking (MPPT) ref MPPT It was decided that, after the failure occurred, P ref Switching to the mechanical power P output by the inherent mechanical characteristic curve of the wind turbine mThe decision is made that the output power decreases as the rotor speed increases after switching, thus achieving adaptive adjustment of the grid-side active power during faults.

[0015] In conjunction with the first aspect, in some implementations of the first aspect, the system further includes: the calculation process of the grid-side additional control module outputting the angular frequency of the grid-side converter after passing it through the first transient stabilization controller and the limiter to obtain the grid-side compensation value for inertia self-sustaining control, including: the grid-side compensation value is calculated by the following formula: ΔX=G ts1 (s)·Δω, where s is the Laplace operator, Δω is the angular frequency of the grid-side converter output voltage, and G ts1 (s) is the transfer function of the first transient stable controller, which can be of different types. A typical example is the proportional-integral controller, whose expression is: G ts1 (s)=(k p1 +k i1 / s), where k p1 k i1 These are the proportional coefficient and integral coefficient in the first transient stable controller, respectively.

[0016] In conjunction with the first aspect, in some implementations of the first aspect, the system further includes: a calculation process in which the machine-side coupling control module outputs the machine-side reference compensation value for inertia self-sustaining control after passing the converter grid-side compensation reference value through the second transient stability controller and the limiter, including: the machine-side reference compensation value is calculated by the following formula: ΔY=G ts2 (s)·ΔX, where s is the Laplace operator, ΔX is the compensation value output by the grid-side additional control module, and G ts2 (s) is the transfer function of the second transient stable controller, which is a proportional-integral controller, and its expression is: G ts2 (s)=(k p2 +k i2 / s), where k p2 k i2 These are the proportional coefficient and integral coefficient in the second transient stable controller, respectively.

[0017] In conjunction with the first aspect, in some implementations of the first aspect, the system further includes: the machine-side additional control module converts the angular frequency output by the grid-side converter into a torque compensation current through a third transient stability controller, based on the torque current mapping coefficient, including: the torque compensation current is calculated by the following formula: Δi s =k i-p ·G ts3 (s)·Δω, where k i-p Here, is the torque-current mapping coefficient, s is the Laplace operator, Δω is the angular frequency of the grid-side converter output voltage, and G is the torque-current mapping coefficient. ts3(s) is the transfer function of the third transient stable controller, which uses a proportional-derivative controller, and its expression is: G ts3 (s)=(k p3 +k i3 s), where k p3 k i3 These are the proportional coefficient and integral coefficient in the third transient stability controller, respectively.

[0018] In conjunction with the first aspect, in some implementations of the first aspect, the system further includes: the torque current mapping coefficient of the machine-side additional control module is calculated as: k i-p =2 / 3n p ψ f ω s , where n p Let ψ be the extreme logarithm. f For magnetic flux linkage, ω s This refers to the stator angular velocity.

[0019] In conjunction with the first aspect, in some implementations of the first aspect, the system further includes: a first transient stability controller G of the network-side additional control module. ts1 (s), the second transient stability controller G of the machine-side coupling control module ts2 (s) The third transient stability controller G of the machine-side auxiliary control module ts3 (s) Different types of specific controllers may be used, including but not limited to proportional controllers, proportional-integral controllers and proportional-derivative controllers.

[0020] In another aspect of the present invention, in order to achieve the above-mentioned objective, a terminal device is disclosed, including a memory, a processor, and a computer program stored in the memory and capable of running on the processor. The memory stores the computer program capable of running on the processor. When the processor loads and executes the computer program, it employs the direct-drive grid-type wind turbine generator control system with inertia self-sustaining function as described above.

[0021] In another aspect of the present invention, in order to achieve the above-mentioned objective, a computer-readable storage medium is disclosed, wherein a computer program is stored in the computer-readable storage medium, and when the computer program is loaded and executed by a processor, a direct-drive grid-type wind turbine generator control system with inertia self-sustaining function as described above is employed.

[0022] The beneficial effects of this invention are:

[0023] This invention can simultaneously enhance the inertia and damping performance of grid-connected wind turbines on both the turbine and grid sides, effectively improving the system's transient stability and fault ride-through capability. It can combine turbine-side and grid-side control interaction to achieve power balance of wind turbine units under fault conditions, and can quickly adjust DC voltage to avoid inverter DC overvoltage protection disconnection from the grid, ensuring the system's inertia self-sustaining capability under fault conditions.

[0024] This invention outperforms traditional solutions in terms of transient inertia and frequency support, and achieves excellent inertia response characteristics across both fast and slow time scales. Specifically, the coordinated operation of the machine side and grid side enables direct interactive coupling between DC voltage and motor control, thereby achieving a high degree of coupling between the actual inertia of rotating components and the power grid. On one hand, this invention utilizes the rapid dynamic response control of DC capacitors and grid-side transient power regulation to actively store unbalanced power, providing a fast virtual inertia response and achieving the converter's inertia-frequency support capability on a fast time scale. On the other hand, this invention utilizes the large amount of kinetic energy of the machine-side rotor to absorb power imbalances during grid disturbances, simulating synchronous external characteristics, and leveraging the rotating motor's inertia support capability to increase the actual inertia of the system. The coordinated control across fast and slow time scales ensures the system's inertia self-sustaining capability under fault conditions, guaranteeing reliable fault ride-through and grid support. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a structural diagram of the grid-side and turbine-side control method for the general grid-connected wind turbine in this invention;

[0027] Figure 2 This is a schematic diagram of the structure of the first type of grid-connected fan in an embodiment of the present invention;

[0028] Figure 3 This is a structural diagram of the grid-side control method for the first type of grid-connected wind turbine in an embodiment of the present invention;

[0029] Figure 4 This is a structural diagram of the machine-side control method for the first type of grid-connected wind turbine in an embodiment of the present invention;

[0030] Figure 5 This is a schematic diagram of the structure of the second type of grid-connected fan in an embodiment of the present invention;

[0031] Figure 6 This is a structural diagram of the grid-side control method for the second type of grid-connected wind turbine in an embodiment of the present invention;

[0032] Figure 7This is a structural diagram of the machine-side control method for the second type of grid-connected wind turbine in an embodiment of the present invention;

[0033] Figure 8 This is a schematic diagram illustrating the control effect of the first type of grid-connected wind turbine in an embodiment of the present invention;

[0034] Figure 9 This is a schematic diagram illustrating the control effect of the second type of grid-connected wind turbine in an embodiment of the present invention; Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Example 1:

[0037] like Figure 1 As shown, the control system for a direct-drive grid-connected wind turbine generator with inertia self-sustaining function includes:

[0038] The grid-side additional control module is used to obtain the angular frequency of the grid-side converter output. After the angular frequency of the grid-side converter output is passed through the first transient stability controller and the limiter, the voltage compensation value for inertia self-sustaining control is output. The voltage compensation value is subtracted from the preset grid-side reference value, and the grid-side compensation reference value of the converter is output to realize the transient grid-side stability enhancement.

[0039] The grid-side compensation reference value of the converter is sent to the machine-side coupling control module, and the angular frequency output by the grid-side converter is sent to the machine-side auxiliary control module.

[0040] The angular frequency of the grid-side converter output obtained by the grid-side additional control module is processed by the grid-side power control module.

[0041] The system also includes a grid-side reference adjustment module and a power synchronization control module.

[0042] The grid-side reference adjustment module is used to adjust the grid-side active power reference value P during a fault. ref The power synchronization control module is used to calculate the angular frequency Δω of the converter output voltage based on the active power and active power reference value of the grid-side converter, and use it as the angular frequency of the grid-side converter output to the grid-side auxiliary control module.

[0043] The adjustment process of the grid-side reference adjustment module includes: under normal operation, the active power reference value P ref Output P controlled by Maximum Power Point Tracking (MPPT)ref MPPT It was decided that, after the failure occurred, P ref Switching to the mechanical power P output by the inherent mechanical characteristic curve of the wind turbine m The decision is made that the output power decreases as the rotor speed increases after switching, thus achieving adaptive adjustment of the grid-side active power during faults.

[0044] The grid-side additional control module calculates the grid-side compensation value for inertia self-sustaining control by passing the angular frequency output from the grid-side converter through the first transient stabilization controller and the limiter. The calculation process includes: the grid-side compensation value is calculated using the following formula: ΔX = G ts1 (s)·Δω, where s is the Laplace operator, Δω is the angular frequency of the grid-side converter output voltage, and G ts1 (s) is the transfer function of the first transient stable controller, which can use different types of specific controllers (including but not limited to proportional-integral, proportional-derivative, low-pass, or dual second-order filter controllers, etc.). A typical type is the proportional-integral controller, whose expression is: G ts1 (s)=(k p1 +k i1 / s), where k p1 k i1 These are the proportional coefficient and integral coefficient in the first transient stable controller, respectively.

[0045] The first transient stability controller G ts1 (s) The optional controller also includes a proportional controller G ts1 (s)=k p1 Proportional-derivative controller G ts1 (s)=(k p1 +k d1 s), low-pass filter G ts1 (s)=k·ω c / (s+ω c ) etc., where k p1 k d1 These are the proportional and derivative coefficients of the proportional-derivative controller, k and ω, respectively. c These represent the DC gain and cutoff frequency of the low-pass filter, respectively. The proportional controller design is straightforward and simple, but it cannot address the problem of the grid-side converter's balance point not existing under severe grid faults; while the proportional-derivative controller offers a faster dynamic response, it cannot eliminate static errors; the low-pass filter can reduce high-frequency noise, but the introduced phase lag may worsen system stability. In this application's case, a proportional-integral controller G is selected. ts1 (s)=(k p1 +k i1The parameter design is relatively simple, which can solve the problem of the absence of a balance point in the grid-side converter, significantly improve the inertia and damping performance of the grid-side synchronization link, and enhance the transient stability of the system.

[0046] The machine-side coupling control module is used to output the machine-side reference compensation value for inertia self-sustaining control after the grid-side compensation reference value of the converter is passed through the second transient stability controller and the limiter. The difference between the machine-side reference compensation value and the preset machine-side reference is calculated, and the machine-side compensation reference value of the converter is output to realize the stability enhancement of the machine side.

[0047] The machine-side coupling control module outputs the machine-side reference compensation value for inertia self-sustaining control after the converter grid-side compensation reference value is processed by the second transient stability controller and the limiter. The calculation process includes: the machine-side reference compensation value is calculated by the following formula: ΔY=G ts2 (s)·ΔX, where s is the Laplace operator, ΔX is the compensation value output by the grid-side additional control module, and G ts2 (s) is the transfer function of the second transient stable controller, which can use different types of specific controllers (including but not limited to proportional-integral, proportional-derivative, low-pass, or dual second-order filter controllers, etc.). A typical type is the proportional-integral controller, whose expression is: G ts2 (s)=(k p2 +k i2 / s), where k p2 k i2 These are the proportional coefficient and integral coefficient in the second transient stable controller, respectively.

[0048] The second transient stability controller G ts2 (s) The optional controller also includes a proportional controller G ts2 (s)=k p2 Proportional-derivative controller G ts2 (s)=(k p2 +k d2 s), etc., where k p2 k d2 These are the proportional and derivative coefficients of the proportional-derivative controller, respectively. Similarly, the proportional controller is straightforward and simple to design, but it cannot be applied to situations where the input has static errors; while the proportional-derivative controller may further amplify high-frequency noise interference of ΔX, weakening the control effect; in this application's case, a proportional-integral controller G is chosen. ts2 (s)=(k p2 +k i2 / s), through the proportional element k p2 Rapid response to system disturbances, while utilizing the integral element k i2 / s effectively eliminates static errors, smoothly adjusts the power flow between the machine side and the grid side, enhances the inertial coupling support capability of the machine side and the grid side, absorbs the power imbalance between the machine side and the grid side, and enhances the transient stability of the system.

[0049] The additional control module on the generator side is used to convert the angular frequency output by the grid-side converter into torque compensation current based on the torque current mapping coefficient through the third transient stability controller. The torque compensation current is then subtracted from the preset generator-side reactive current reference value to output the generator-side reactive current compensation reference value, thereby avoiding the deterioration of the power imbalance of the wind turbine and improving the transient stability of the grid-connected wind turbine under grid faults.

[0050] The additional control module on the machine side processes the angular frequency output by the grid-side converter through a third transient stability controller. Based on the torque current mapping coefficient, the process converts this angular frequency into a torque compensation current, including: the torque compensation current is calculated using the following formula: Δi s =k i-p ·G ts3 (s)·Δω, where k i-p Here, is the torque-current mapping coefficient, s is the Laplace operator, Δω is the angular frequency of the grid-side converter output voltage, and G is the torque-current mapping coefficient. ts3 (s) is the transfer function of the third transient stable controller, which can use different types of specific controllers (including but not limited to proportional-derivative, lead phase compensation, or dual second-order filter controllers). A typical type is the proportional-derivative controller, whose expression is: G ts3 (s)=(k p3 +k i3 s), where k p3 k i3 These are the proportional coefficient and integral coefficient in the third transient stability controller, respectively.

[0051] The torque current mapping coefficient of the additional control module on the machine side is calculated as follows: k i-p =2 / 3n p ψ f ω s , where n p Let ψ be the extreme logarithm. f For magnetic flux linkage, ω s This refers to the stator angular velocity.

[0052] The third transient stability controller G ts3 (s) Optional controllers also include proportional controllers, etc. Similarly, proportional controllers are straightforward and simple to design, but they may suffer from response lag and under-regulation when dealing with fast dynamic processes; in this application's case, a proportional-integral controller G is selected. ts3 (s)=(k p3 +k i3 s), through the proportional element kp3 Rapid response to unbalanced power, while utilizing the differentiating element k i3 It significantly suppresses overshoot, reduces oscillation, and improves the damping characteristics of the system, ultimately achieving rapid compensation of torque current and enhancing the stability and robustness of the system during transient processes.

[0053] Specifically, the system also includes:

[0054] The integrator module is used to generate the voltage phase based on the calculated converter output voltage frequency and input it to the voltage reference value synthesis module.

[0055] The engine-side power reference adjustment module is used to adjust the engine-side power reference value P during a fault. sref ;

[0056] The machine-side reference zero steady-state error control module is used to achieve zero steady-state error tracking of the actual power / voltage value of the machine-side converter to the compensation reference value output by the machine-grid coupling control module, and to obtain the preset machine-side reactive current reference.

[0057] Specifically, the present invention will be further illustrated below through embodiments:

[0058] Figure 1 Regarding the structure of the control method for the grid-side portion of the general grid-connected wind turbine in this invention, P ref P is the grid-side power reference, and P is the actual grid-side power. ref The difference between P and P is used to obtain the angular frequency error Δω of the synchronization link after passing through the power synchronization link, and then compared with the grid angular frequency ω. g The summation yields the output angular frequency ω of the synchronization element. vsg After passing through the integrator, the reference angle θ for grid-side control of grid-type wind turbines is obtained. vsg .

[0059] This invention mainly includes a grid-side control scheme for grid-connected wind turbines: 1-grid-side reference adjustment module and 2-grid-side supplementary control module. The power reference adjustment module switches to enhanced MPPT control after a fault, and the original power reference P... ref MPPT controls the output P ref MPPT The decision is made to switch to the wind turbine's inherent mechanical characteristic curve after a fault; 2- The grid-side additional control module obtains the angular frequency error Δω output by the grid active power synchronization link, and after passing through the first transient stability controller and limiter, obtains the grid-side virtual power or DC voltage compensation value ΔX for transient stability enhancement.

[0060] Figure 1 Regarding the structure of the control method for the general grid-connected wind turbine side portion in this invention, Y refY is the reference for the generator-side power, ΔY is the actual generator-side power, and ΔY is the virtual generator-side power or DC voltage compensation value.

[0061] This invention provides a turbine-side control scheme for grid-connected wind turbines, primarily comprising: 1-turbine-side reference adjustment module, 3-grid-generator coupling control module, and 4-turbine-side supplementary control module. Specifically, the 1-turbine-side reference adjustment module can switch from the original MPPT control to enhanced MPPT control after a fault, with the original power reference P... ref MPPT controls the output P ref MPPT The decision is made to switch to the wind turbine's inherent mechanical characteristic curve after a fault; the 3-grid coupling control module obtains the grid-side virtual power or DC voltage compensation value ΔX, which, after passing through the second transient stabilization controller and limiter, yields the DC voltage / power compensation value ΔY for the inertia and damping correction of the synchronization link; the 4-grid-side additional control module obtains the angular frequency error Δω output by the grid active power synchronization link, which, after passing through the third transient stabilization controller and through 2 / 3n... p ψ f ω s The torque-current mapping coefficient is converted into torque compensation current Δi s Compensation current Δi s Compared with the preset machine-side reactive current reference i sqref After subtraction, the reference value for reactive current compensation on the converter side is obtained, reducing the rotor current reference value i during fault periods. sqref This enables the rotor to quickly absorb transient energy imbalances during transient periods.

[0062] In summary, this invention can simultaneously utilize DC capacitors and rotors to regulate transient imbalance energy on both the turbine side and the grid side during faults, thereby improving the transient stability and grid support capability of grid-connected wind turbines.

[0063] The embodiments of the present invention also provide application examples in two types of grid-type wind turbine systems.

[0064] Embodiment 1 of the present invention:

[0065] Figure 2 This is a schematic diagram of the structure of the first type of grid-connected fan in this invention;

[0066] In the first type of grid-connected wind turbine, U dc and U * dc These represent the actual DC voltage and its reference value, respectively; i sdref i sqref These are the reference dq components of the machine-side current, respectively. e Q e These represent the active and reactive power outputs of the grid-side inverter, respectively. refThis is the active power reference value for the grid-side inverter. The power synchronization control stage uses a virtual synchronous generator (VSG). E is the reactive power voltage control output reference voltage, v d v q These represent the dq components of the grid-side output voltage. gd i gq These are the dq components of the grid-side output current, respectively.

[0067] Specifically, the grid-side control of Category 1 grid-connected wind turbines also includes:

[0068] The voltage reference value synthesis module generates a common coupling point (PCC) voltage reference value based on the amplitude and phase of the grid-side converter output voltage, and inputs the output voltage reference value into the voltage and current control module.

[0069] The voltage and current control module is used to compare the reference value of the common coupling point (PCC) voltage of the grid-side converter with the actual value to generate the dq current reference value of the grid-side converter. The current reference value is further compared with the actual value to generate the output voltage reference value of the bridge arm of the machine-side converter. This voltage reference value is then input into the pulse width modulation module.

[0070] The grid-side pulse width modulation (PWM) module is used to generate the grid-side converter drive signal based on the voltage reference value output by the voltage and current control module.

[0071] The machine-side control of Category 1 grid-connected wind turbines also includes:

[0072] Phase-locked loop (PLL) module: used to extract the rotor angle θ on the machine side. r , used for the dq axis coordinate transformation of the control link;

[0073] DC voltage outer loop control module: Used to compare the reference value and the actual value of the DC side voltage of the wind turbine to generate the stator dq axis current i of the turbine-side converter. sqref and i sdref ;

[0074] Current control module: used to compare the current reference value with the actual value to generate the machine-side converter bridge arm output voltage reference value, and input this voltage reference value into the pulse width modulation module;

[0075] Machine-side pulse width modulation (PWM) module: used to generate machine-side converter drive signals based on the voltage reference value output by the current control module.

[0076] Figure 3 This is a structural diagram of the grid-side control method for the first type of grid-connected wind turbine in this invention; in the diagram, P ref P is the grid-side power reference, and J is the actual grid-side power. J represents virtual inertia, and D... p ω is the virtual damping coefficient. gLet ω be the angular frequency of the power grid, and Δω be the angular frequency error of the output. The derivative of Δω, ω vsg To output the angular frequency θ for the network synchronization link vsg The angle is output for the synchronization stage.

[0077] The grid-side control scheme for the first type of grid-connected wind turbines in this invention mainly includes a 1-1-grid-side power reference adjustment module and a 1-2-grid-side supplementary control module. Among them, the synchronization link power reference P... ref MPPT Determined by MPPT control, calculated as k opt ω opt 3 , where k opt ω is a constant representing the maximum power coefficient. opt ω is the optimal rotor speed corresponding to a given wind speed. r The rotor angular frequency; the 1-1-power reference adjustment module switches to enhanced MPPT control after a fault, and the power reference P before the fault occurred. ref MPPT controls the output P ref MPPT The decision is made to switch to the mechanical power P output by the inherent mechanical characteristic curve of the wind turbine after a failure. m The decision is made as follows: 1-2- The grid-side additional control module obtains the angular frequency error Δω output from the grid active power synchronization link. After passing through the first transient stability controller (a proportional-integral controller is used in this embodiment), the grid-side virtual power compensation value ΔP, which is aimed at enhancing transient stability, is obtained. s The compensation value ΔP s Compared with the preset grid-side power reference P ref After subtraction, the grid-side compensation reference value of the converter is obtained. This compensation can avoid transient instability caused by grid-side power imbalance. K p and K i These are the proportional and integral gains of the PI controller in the 1-2-network-side additional control module, respectively.

[0078] Figure 4 This is a structural diagram of the machine-side control method for the first type of grid-connected wind turbine in this invention; in the diagram, U dc and U * dc These represent the actual DC voltage and its reference value, respectively; ΔV c 2 i is the DC voltage compensation value. sqref It serves as the reference for reactive current on the machine side.

[0079] The grid-side control scheme for the first type of grid-connected wind turbines in this invention mainly includes a 1-3-machine-grid coupling control module and a 1-4-machine-side supplementary control module. The 1-3-machine-grid coupling control module acquires the grid-side virtual power compensation value ΔP. s It is then passed through a second transient stabilization controller (in this embodiment, a proportional controller is used, with a power-DC voltage conversion coefficient of 1 / K). s After that, a DC voltage compensation value ΔV is generated. c 2 The 1-4-machine-side auxiliary control module obtains the angular frequency error Δω output from the grid active power synchronization link, which is then used by the third transient stability controller (a proportional-derivative controller is used in this embodiment) to generate compensation power, which is then transmitted through 2 / 3n p ψ f ω s The torque-current mapping coefficient is converted into torque compensation current Δi s , where n p Let ψ be the extreme logarithm. f For magnetic flux linkage, ω s Stator angular velocity. Compensation current Δi s Compared with the preset machine-side reactive current reference i sqref After subtraction, the reference value for reactive current compensation on the converter side is obtained.

[0080] Embodiment 2 of the present invention:

[0081] Figure 5 This is a schematic diagram of the structure of the second type of grid-connected fan in this invention;

[0082] In Category 2 grid-connected wind turbines, the power reference P of the grid synchronization link ref The voltage is given by DC voltage control; the grid synchronization link uses a virtual synchronous machine (VSG) for control. The power reference P of the synchronization link... ref Determined by MPPT control; U dc and U * dc These represent the actual DC voltage and its reference value, respectively; k pdc and k idc These represent the proportional and integral gains of the DC voltage controller, respectively; ω g ω and ω are the angular frequencies of the grid voltage and the grid output voltage, respectively; J p and D p These are virtual inertia and virtual damping, respectively.

[0083] Specifically, the grid-side control of the second type of grid-connected wind turbines also includes:

[0084] The voltage reference value synthesis module generates a common coupling point (PCC) voltage reference value based on the amplitude and phase of the grid-side converter output voltage, and inputs the output voltage reference value into the voltage and current control module.

[0085] The voltage and current control module is used to compare the reference value of the common coupling point (PCC) voltage of the grid-side converter with the actual value to generate the dq current reference value of the grid-side converter. The current reference value is further compared with the actual value to generate the output voltage reference value of the bridge arm of the machine-side converter. This voltage reference value is then input into the pulse width modulation module.

[0086] The grid-side pulse width modulation (PWM) module is used to generate the grid-side converter drive signal based on the voltage reference value output by the voltage and current control module.

[0087] The machine-side control of Category 2 grid-connected wind turbines also includes:

[0088] Phase-locked loop (PLL) module: used to extract the rotor angle θ on the machine side. r , used for the dq axis coordinate transformation of the control link;

[0089] Machine-side power control module: Used to compare the reference value and actual value of the wind turbine's machine-side power to generate the stator dq-axis current i of the machine-side converter. sqref and i sdref ;

[0090] Current control module: used to compare the current reference value with the actual value to generate the machine-side converter bridge arm output voltage reference value, and input this voltage reference value into the pulse width modulation module;

[0091] Machine-side pulse width modulation (PWM) module: used to generate machine-side converter drive signals based on the voltage reference value output by the current control module.

[0092] Figure 6 This is a structural diagram of the grid-side control method for the second type of grid-connected wind turbine in this invention; in the diagram, U dc and U * dc represents the actual DC voltage and its reference value, respectively; P s P is the rotor-side power of the wind turbine. ref For grid-side power reference, P g This represents the actual power on the grid side. J represents virtual inertia, and D... p ω is the virtual damping coefficient. g Let ω be the angular frequency of the power grid, and Δω be the angular frequency error of the output. The derivative of Δω, ω vsg To output the angular frequency θ for the network synchronization link vsg The angle is output for the synchronization stage.

[0093] The grid-side control scheme for the second type of grid-connected wind turbine in this invention mainly includes a 2-2-grid-side supplementary control module. The 2-2-grid-side supplementary control module obtains... After passing through the first transient stabilization controller (a PI controller is used in this embodiment), the grid-side virtual DC voltage compensation value ΔU for enhancing transient stability is obtained. dc 2 k p and k i These represent the proportional and integral gains of the PI controller in the 2-2-network-side additional control module, respectively. The compensation value ΔU 2 dc Compared with the preset grid-side DC voltage reference ΔU 2 dcref After addition, a reference value for DC voltage after compensation is obtained, which realizes the adjustment of grid-side unbalanced power and the enhancement of stability under transient conditions.

[0094] Figure 7 This is a structural diagram of the machine-side control method for the second type of grid-connected wind turbine in this invention; in the diagram, ΔP s i is the power compensation value on the machine side. sqref It serves as the reference for reactive current on the machine side.

[0095] The grid-side control scheme for the second type of grid-connected wind turbine in this invention mainly includes a 2-1-turbine-side power reference adjustment module, a 2-3-grid coupling control module, and a 2-4-turbine-side supplementary control module. Among them, the 2-1-turbine-side power reference adjustment module switches to enhanced MPPT control after a fault, and the original power reference P... ref MPPT controls the output P ref MPPT The decision is made to switch to the mechanical power P output by the inherent mechanical characteristic curve of the wind turbine after a failure. m Decision; 2-3-The machine-grid coupling control module obtains the grid-side virtual power compensation value ΔU dc 2 After multiplying it by the absolute value of the machine-side angular frequency error, |Δω|, the result is used by a second transient stabilization controller (in this embodiment, a proportional-integral controller) to generate the machine-side power compensation value ΔP. s 2 The 2-4 machine-side additional control module obtains the angular frequency error Δω output from the grid active power synchronization link, and generates compensation power through the third transient stability controller (a proportional-derivative controller is used in this embodiment), which then passes through 2 / 3n p ψfω s The torque-current mapping coefficient is converted into torque compensation current Δi s , where n p Let ψ be the extreme logarithm. f For magnetic flux linkage, ω s Stator angular velocity. Compensation current Δis Compared with the preset machine-side reactive current reference i sqref After subtraction, the reference value for reactive current compensation on the converter side is obtained.

[0096] Figure 8 This is a schematic diagram of the control effect of the first type of grid-connected wind turbine in an embodiment of the present invention. The grid voltage drops to 40% of its nominal value and lasts for 625ms. Figure 8 (a) and (b) illustrate the effects of using the conventional control scheme and the control scheme of the present invention, respectively. Compared with the conventional control, the Type 1 grid-connected wind turbines that incorporate the inertia self-sustaining function proposed in this invention can maintain synchronization with the grid under fault conditions, avoiding the risks of transient instability and power angle oscillation. This control method can simultaneously avoid AC side overcurrent and DC overvoltage, improving the fault ride-through capability of the wind turbine.

[0097] Figure 9 This is a schematic diagram of the control effect of the second type of grid-connected wind turbine in an embodiment of the present invention. The grid voltage drops to 30% of its nominal value and lasts for 625ms. Figure 9 (a) and (b) illustrate the effects of using the conventional control scheme and the control scheme of the present invention, respectively. Similarly, compared with conventional control, the inertia self-sustaining control scheme proposed in this invention significantly improves the transient stability of grid-connected wind turbines under grid faults, avoids AC overcurrent and DC overvoltage problems, and achieves reliable system operation and grid support. In summary, the above control effects verify the applicability and effectiveness of the control scheme of the present invention in transient stability control and fault ride-through of direct-drive grid-connected wind turbines.

[0098] Based on the same inventive concept, this invention also provides a computer device, comprising: one or more processors, and a memory for storing one or more computer programs; the programs include program instructions, and the processor executes the program instructions stored in the memory. The processor may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, used to implement one or more instructions, specifically for loading and executing one or more instructions stored in a computer storage medium to implement the above-described method.

[0099] It should be further explained that, based on the same inventive concept, the present invention also provides a computer storage medium storing a computer program, which, when executed by a processor, performs the above-described method. This storage medium can be any combination of one or more computer-readable media. The computer-readable medium can be a computer-readable signal medium or a computer-readable storage medium. The computer-readable storage medium can be, for example, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of computer-readable storage media (a non-exhaustive list) include: an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination thereof. In the present invention, the computer-readable storage medium can be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device.

[0100] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this disclosure. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0101] The foregoing has shown and described the basic principles, main features, and advantages of this disclosure. Those skilled in the art should understand that this disclosure is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this disclosure. Various changes and modifications can be made to this disclosure without departing from its spirit and scope, and all such changes and modifications fall within the scope of this disclosure as claimed.

Claims

1. A control system for a direct-drive grid-connected wind turbine generator set with inertia self-sustaining function, characterized in that, include: The grid-side additional control module is used to obtain the angular frequency of the grid-side converter output. After the angular frequency of the grid-side converter output is passed through the first transient stability controller and the limiter, the grid-side compensation value for inertia self-sustaining control is output. The grid-side compensation value is subtracted from the preset grid-side reference value, and the grid-side compensation reference value of the converter is output to realize the stability enhancement of the transient grid side. The grid-side compensation reference value of the converter is sent to the machine-side coupling control module, and the angular frequency output by the grid-side converter is sent to the machine-side auxiliary control module. The machine-side coupling control module is used to output the machine-side reference compensation value for inertia self-sustaining control after the grid-side compensation reference value of the converter is passed through the second transient stability controller and the limiter. The difference between the machine-side reference compensation value and the preset machine-side reference is calculated, and the machine-side compensation reference value of the converter is output to realize the stability enhancement of the machine side. The additional control module on the generator side is used to convert the angular frequency output by the grid-side converter into torque compensation current based on the torque current mapping coefficient through the third transient stability controller. The torque compensation current is then subtracted from the preset generator-side reactive current reference value to output the generator-side reactive current compensation reference value, thereby avoiding the deterioration of the power imbalance of the wind turbine and improving the transient stability of the grid-connected wind turbine under grid faults.

2. The control system for a direct-drive grid-type wind turbine generator with inertia self-sustaining function according to claim 1, characterized in that, The angular frequency of the grid-side converter output obtained by the grid-side additional control module is processed by the grid-side power control module. The system also includes a grid-side reference adjustment module and a power synchronization control module.

3. The control system for a direct-drive grid-type wind turbine generator with inertia self-sustaining function according to claim 2, characterized in that, The grid-side reference adjustment module is used to adjust the grid-side active power reference value P during a fault. ref The power synchronization control module is used to calculate the angular frequency Δω of the converter output voltage based on the active power and active power reference value of the grid-side converter, and use it as the angular frequency of the grid-side converter output to the grid-side auxiliary control module.

4. The control system for a direct-drive grid-type wind turbine generator with inertia self-sustaining function according to claim 3, characterized in that, The adjustment process of the grid-side reference adjustment module includes: under normal operation, the active power reference value P ref Output P controlled by Maximum Power Point Tracking (MPPT) ref MPPT It was decided that, after the failure occurred, P ref Switching to the mechanical power P output by the inherent mechanical characteristic curve of the wind turbine m The decision is made that the output power decreases as the rotor speed increases after switching, thus achieving adaptive adjustment of the grid-side active power during faults.

5. The control system for a direct-drive grid-type wind turbine generator with inertia self-sustaining function according to claim 1, characterized in that, The grid-side additional control module calculates the grid-side compensation value for inertia self-sustaining control by passing the angular frequency output from the grid-side converter through the first transient stabilization controller and the limiter. The calculation process includes: the grid-side compensation value is calculated using the following formula: ΔX = G ts1 (s)·Δω, where s is the Laplace operator, Δω is the angular frequency of the grid-side converter output voltage, and G ts1 (s) is the transfer function of the first transient stable controller, which uses a proportional-integral controller, and its expression is: G ts1 (s)=(k p1 +k i1 / s), where k p1 k i1 These are the proportional coefficient and integral coefficient in the first transient stable controller, respectively.

6. The control system for a direct-drive grid-type wind turbine generator with inertia self-sustaining function according to claim 1, characterized in that, The machine-side coupling control module outputs the machine-side reference compensation value for inertia self-sustaining control after the converter grid-side compensation reference value is processed by the second transient stability controller and the limiter. The calculation process includes: the machine-side reference compensation value is calculated by the following formula: ΔY=G ts2 (s)·ΔX, where s is the Laplace operator, ΔX is the compensation value output by the grid-side additional control module, and G ts2 (s) is the transfer function of the second transient stable controller, which is a proportional-integral controller, and its expression is: G ts2 (s)=(k p2 +k i2 / s), where k p2 k i2 These are the proportional coefficient and integral coefficient in the second transient stable controller, respectively.

7. The control system for a direct-drive grid-type wind turbine generator with inertia self-sustaining function according to claim 1, characterized in that, The additional control module on the machine side processes the angular frequency output by the grid-side converter through a third transient stability controller. Based on the torque current mapping coefficient, the process converts this angular frequency into a torque compensation current, including: the torque compensation current is calculated using the following formula: Δi s =k i-p ·G ts3 (s)·Δω, where k i-p Here, is the torque-current mapping coefficient, s is the Laplace operator, Δω is the angular frequency of the grid-side converter output voltage, and G is the torque-current mapping coefficient. ts3 (s) is the transfer function of the third transient stable controller, which uses a proportional-derivative controller, and its expression is: G ts3 (s)=(k p3 +k i3 s), where k p3 k i3 These are the proportional coefficient and integral coefficient in the third transient stability controller, respectively.

8. The control system for a direct-drive grid-type wind turbine generator with inertia self-sustaining function according to claim 1, characterized in that, The torque current mapping coefficient of the additional control module on the machine side is calculated as follows: k i-p =2 / 3n p ψ f ω s , where n p Let ψ be the extreme logarithm. f For magnetic flux linkage, ω s This refers to the stator angular velocity.

9. The control system for a direct-drive grid-type wind turbine generator with inertia self-sustaining function according to claim 1, characterized in that, The first transient stability controller G of the network-side additional control module ts1 (s), the second transient stability controller G of the machine-side coupling control module ts2 (s) The third transient stability controller G of the machine-side auxiliary control module ts3 (s) Different types of specific controllers may be used, including but not limited to proportional controllers, proportional-integral controllers and proportional-derivative controllers.

10. A terminal device, comprising a memory, a processor, and a computer program stored in the memory and capable of running on the processor, characterized in that, The memory stores a computer program that can run on a processor. When the processor loads and executes the computer program, it employs a direct-drive grid-type wind turbine generator control system with inertia self-sustaining function as described in any one of claims 1 to 9.

11. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is loaded and executed by the processor, it employs the direct-drive grid-type wind turbine generator control system with inertia self-sustaining function as described in any one of claims 1 to 9.

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