Wind storage aggregation system virtual network construction control method and device suitable for operation under weak network

Abstract

The invention discloses a wind storage aggregation system virtual network construction control method and device suitable for operation under a weak network, and belongs to the field of converter control, and the method comprises the steps: obtaining a grid-connected point voltage vector, and obtaining a grid-connected point voltage phase through a phase-locked loop; a virtual voltage vector is generated based on the virtual network construction control loop, the difference between the virtual voltage vector and the grid-connected point voltage vector is obtained, and virtual network construction current is obtained through virtual impedance; determining a basic current reference value of a current inner ring; multiplying the virtual network construction current by a gain coefficient to obtain an additional current reference value, superposing the additional current reference value with a basic current reference value to obtain a reference voltage, and processing the reference voltage through a PWM controller to obtain a PWM signal; and constructing a full-order state space model of the fan energy storage aggregation grid-connected system, drawing a characteristic root locus of a state matrix, and determining a gain coefficient range according to the characteristic root locus. According to the method, the risk of next synchronous oscillation of the wind storage aggregation system in the weak power grid is fully considered, and the stability of the wind storage aggregation system in the weak power grid can be improved.

Description

Technical Field

[0001] This invention relates to the field of converter control technology, and in particular to a virtual network construction control method and apparatus for wind-storage aggregation systems operating under weak network conditions. Background Technology

[0002] With the increasing penetration rate of renewable energy, wind power systems are being connected to weak power grids on a large scale. In this scenario, the dynamic interaction between wind turbines and the power grid system is significantly enhanced. As the grid strength decreases, the system exhibits a significant risk of subsynchronous frequency oscillations, seriously threatening the stability of grid operation.

[0003] Grid-based converter control technology is considered an effective means to improve the operational stability of wind power under weak grid conditions, and can suppress oscillations caused by the grid connection of new energy sources to a certain extent. Existing research mostly focuses on using grid-based energy storage control strategies on the AC side to achieve subsynchronous oscillation suppression; however, research on the participation of DC-side energy storage in oscillation suppression within wind-storage aggregation systems is still relatively lacking. In current applications, DC-side energy storage systems are mainly used to absorb unbalanced power output from wind power, and their auxiliary damping potential has not been fully utilized, leading to the difficulty in stable operation of wind-storage aggregation systems based on DC-side energy storage in weak grid environments. Summary of the Invention

[0004] The purpose of this application is to overcome the shortcomings of the prior art and provide a virtual grid construction control method and device for wind-storage aggregation systems operating under weak grid conditions, so as to fully consider the risk of subsynchronous oscillation of traditional wind-storage aggregation systems under weak grid conditions and improve the stability of wind-storage aggregation systems under weak grid conditions.

[0005] Firstly, this application provides a virtual network construction control method for a wind-storage aggregation system operating under weak network conditions, comprising the following steps: Obtain the grid connection point voltage vector, and perform phase-locked loop processing on the grid connection point voltage vector to obtain the grid connection point voltage phase; A virtual voltage vector is generated based on the virtual grid control loop. The virtual voltage vector is then subtracted from the grid connection point voltage vector and passed through a virtual impedance to obtain the virtual grid current. The reference value of the base current of the inner loop d-axis is calculated based on the deviation between the calculated value of the grid active power and the set value of the grid active power. The reference value of the base current of the inner loop q-axis is calculated based on the deviation between the grid connection point voltage vector and the rated value of the AC voltage. The virtual network current is multiplied by the gain coefficient and used as the additional current reference value of the inner current loop. This value is then superimposed on the basic current reference value to generate a reference voltage through the inner current loop. The reference voltage is then sent to the PWM controller after coordinate transformation to obtain the PWM signal. Establish the small-signal differential equations of the entire control system, and based on the small-signal differential equations of the entire control system, construct the full-order state-space model of the wind turbine energy storage aggregation grid-connected system. Based on the full-order state-space model of the wind turbine energy storage aggregation grid-connected system, the eigenvalue trajectory of the state matrix is ​​plotted, and the gain coefficient range is determined according to the eigenvalue trajectory.

[0006] Optionally, a virtual voltage vector is generated based on the virtual grid control loop, and the virtual grid current is obtained by subtracting the virtual voltage vector from the grid connection point voltage vector and passing it through a virtual impedance, including: The virtual network active power and the virtual network active power reference value are input into the active power loop to generate the phase of the virtual voltage vector; The virtual network reactive power and the virtual network reactive power reference value are input into the reactive power loop to generate the amplitude of the virtual voltage vector. The phase and magnitude of the virtual voltage vector are vector-synthesized to obtain the virtual voltage vector. The voltage difference is obtained by subtracting the virtual voltage vector from the grid connection point voltage vector, and the virtual grid current is obtained by controlling the voltage difference through virtual impedance.

[0007] Optionally, the small-signal differential equations for the active power loop and the reactive power loop are: in, This represents the disturbance to the voltage frequency of the virtual network. This represents the disturbance in the virtual grid voltage phase. This represents the disturbance to the voltage amplitude of the virtual network. J and D p These are virtual inertia and damping, respectively. ω n The rated angular frequency, K q The reactive power integral coefficient, u td0 The steady-state value of the d-axis component of the grid connection point voltage. This represents the disturbance of the d-axis component of the grid connection point voltage. This represents the disturbance of the q-axis component of the grid connection point voltage. i vd0 This represents the steady-state value of the d-axis component of the virtual network current. i vq0 This represents the steady-state value of the q-axis component of the virtual network current. This represents the disturbance of the d-axis component of the virtual network current. This represents the disturbance of the q-axis component of the virtual network current.

[0008] Alternatively, the small-signal differential equation for virtual impedance control is expressed as follows: in, L v and R v These are virtual reactance and virtual resistance, respectively. and These represent the disturbances to the d-axis and q-axis components of the virtual network current, respectively. This represents the disturbance in the virtual grid voltage phase. This represents the disturbance to the voltage amplitude of the virtual network. This represents the disturbance of the d-axis component of the grid connection point voltage. This represents the disturbance of the q-axis component of the grid connection point voltage. ω n The rated angular frequency, u n The rated AC voltage. This represents the disturbance in the output phase of the phase-locked loop.

[0009] Optionally, the d-axis base current reference value of the inner current loop. i dref Reference value of q-axis base current in the inner current loop i qref Expressed as follows: in, k pcp and k pci These are the proportional and integral coefficients of the active power loop PI controller, respectively. k qcp and k qci These are the proportional and integral coefficients of the AC voltage loop PI controller, respectively. P Gref and P G These are the setpoint and calculated values ​​of the active power connected to the grid, respectively. u n and u td These represent the rated AC voltage and the d-axis components of the grid connection point voltage, respectively.

[0010] Optionally, the virtual network current is multiplied by a gain coefficient to obtain an additional current reference value for the inner current loop, which is then superimposed on the base current reference value to generate a reference voltage through the inner current loop. This reference voltage is then transformed by coordinates and sent to the PWM controller to obtain a PWM signal, including: Multiply the d-axis and q-axis components of the virtual network current by the gain coefficient to obtain the reference values ​​of the additional d-axis and q-axis components of the current inner loop. The additional current d-axis component reference value, the current inner loop d-axis base current reference value, and the grid-side converter output current d-axis component of the current inner loop are fused together and then used to generate a voltage signal d-axis component through a first current inner loop PI controller; the additional current q-axis component reference value, the current inner loop q-axis base current reference value, and the grid-side converter output current q-axis component of the current inner loop are fused together and then used to generate a voltage signal q-axis component through a second current inner loop PI controller. Multiply the d-axis and q-axis components of the grid connection point voltage by the voltage feedforward coefficient to obtain the reference values ​​of the d-axis and q-axis components of the feedforward voltage. The d-axis component of the grid-side converter output current and the q-axis component of the grid-side converter output current are respectively coupled and compensated to obtain the d-axis component and the q-axis component of the feedforward voltage. The reference value of the d-axis component of the feedforward voltage, the d-axis component of the voltage signal, and the q-axis component of the feedforward voltage are fused to obtain the reference voltage d-axis component; the reference value of the q-axis component of the feedforward voltage, the q-axis component of the voltage signal, and the d-axis component of the feedforward voltage are fused to obtain the reference voltage q-axis component. The d-axis component and q-axis component of the reference voltage are sent to the PWM controller after coordinate transformation to obtain the PWM signal.

[0011] Optionally, the small-signal differential equations of the entire control system include the small-signal differential equations of the phase-locked loop, the active power loop and the reactive power loop, the small-signal differential equations of the virtual impedance control, and the small-signal differential equations of the inner current loop. The expression of the small-signal differential equations of the entire control system is as follows: in, and These represent the disturbances to the d-axis and q-axis components of the grid-side current, respectively. C f For filtering capacitors, L g For grid-side inductance, and These represent the disturbances to the d-axis and q-axis components of the reference voltage, respectively. This represents the disturbance of the d-axis component of the grid connection point voltage. This represents the disturbance of the q-axis component of the grid connection point voltage. ω n The rated angular frequency, and These represent the disturbances in the d-axis and q-axis components of the grid-side converter output current, respectively. Lf This is the machine-side filter inductor.

[0012] Optionally, the expression for the full-order state-space model of the wind turbine energy storage aggregation grid-connected system is: in, A The state matrix, For the state variable matrix, This represents the disturbance in the virtual grid voltage phase. This represents the disturbance to the voltage frequency of the virtual network. This represents the disturbance to the voltage amplitude of the virtual network. and These represent the disturbances to the d-axis and q-axis components of the virtual network current, respectively. This represents the disturbance in the output phase of the phase-locked loop. This is the disturbance output of the phase-locked loop integral controller. and These are the d-axis and q-axis disturbances output by the current loop integral controller, respectively. and These represent the disturbances in the d-axis and q-axis components of the grid-side converter output current, respectively. This represents the disturbance of the d-axis component of the grid connection point voltage. This represents the disturbance of the q-axis component of the grid connection point voltage. and These represent the disturbances to the d-axis and q-axis components of the grid-side current, respectively.

[0013] Optionally, based on the full-order state-space model of the wind turbine energy storage aggregation grid-connected system, the eigenvalue trajectory of the state matrix is ​​plotted, and the gain coefficient range is determined according to the eigenvalue trajectory. This includes determining the eigenvalues ​​of the state matrix based on the full-order state-space model of the wind turbine energy storage aggregation grid-connected system, plotting the eigenvalue trajectory of the state matrix, observing the changes in the eigenvalue trajectory of the state matrix when the grid strength changes and the gain coefficient changes, analyzing the impact on system stability, and determining the gain coefficient range suitable for the operation of the wind turbine energy storage aggregation grid-connected system under weak grid conditions.

[0014] Secondly, this application also provides a virtual grid construction control device for a wind-storage aggregation system operating under weak grid conditions, used to execute the virtual grid construction control method for a wind-storage aggregation system operating under weak grid conditions as described in any one of the first aspects. The virtual grid construction control device for a wind-storage aggregation system operating under weak grid conditions is connected to the power grid. The virtual grid construction control device for a wind-storage aggregation system operating under weak grid conditions includes a grid-connected converter module, a phase-locked loop module, a current inner loop module, a power loop module, a virtual grid construction control loop module, a PWM modulation module, and a coordinate transformation module. The first end of the grid-connected converter module is connected to the power grid. The second end of the grid-connected converter module is connected to the first end of the PWM modulation module. The second end of the PWM modulation module is connected to the first end of the current inner loop module. The third end of the grid-connected converter module is connected to the first end of the phase-locked loop module. The second end of the phase-locked loop module is connected to the coordinate transformation module. The second end of the current inner loop module is connected to the power loop module. The third end of the current inner loop module is connected to the virtual grid construction control loop module.

[0015] This application provides a virtual grid-building control method and device for wind-storage aggregation systems operating under weak grid conditions. It can fully consider the impact of weak grid scenarios on the subsynchronous oscillation characteristics of grid-connected wind turbines, improve the operational stability of wind-storage aggregation systems based on DC-side energy storage assistance under weak grid scenarios, and virtually equivalently represent the parallel connection of grid-connected and grid-building converters based on a single physical converter on the grid side of the wind-storage aggregation system. By controlling the converter to simulate the virtual grid-building current integration, the power characteristics of the converter at the grid connection point are improved. By optimizing the virtual grid-building current gain, the operational stability of wind-storage aggregation systems using grid-connected control of traditional grid-side converters under weak grid scenarios is improved. It has important application value in the current new power systems with a high proportion of wind power integration.

[0016] To make the above-mentioned features and advantages of the invention more apparent and understandable, specific embodiments are described below, and detailed descriptions are provided in conjunction with the accompanying drawings. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments or related technologies of this application, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart of a virtual network control method for a wind-storage aggregation system operating under weak network conditions, provided in one embodiment of this application.

[0019] Figure 2This is a control block diagram of steps S1 to S4 in a virtual network construction control method for a wind-storage aggregation system operating under weak network conditions, provided in one embodiment of this application.

[0020] Figure 3 This is a flowchart of step S2 in a virtual network control method for a wind-storage aggregation system operating under weak network conditions, provided in one embodiment of this application.

[0021] Figure 4 This is a flowchart of step S4 in a virtual network control method for a wind-storage aggregation system operating under weak network conditions, provided in one embodiment of this application.

[0022] Figure 5 In one embodiment of this application, the gain coefficient varies with the short-circuit ratio (SCR) in a virtual network control method for a wind-storage aggregation system operating under weak network conditions. k =0 and gain coefficient k Eigenvalue locus diagram of the state matrix when = 0.5.

[0023] Figure 6 This is an eigenvalue trajectory diagram of the state matrix when the gain coefficient changes, provided in one embodiment of the present application for a virtual network control method for a wind-storage aggregation system operating under weak network conditions.

[0024] Figure 7 This is a power waveform diagram of the following network control and additional virtual network control when the short-circuit ratio changes suddenly in a virtual network control method for a wind-storage aggregation system operating under weak network conditions, provided in one embodiment of this application.

[0025] Figure 8 This is a schematic diagram of a virtual network control device for a wind-storage aggregation system operating under weak network conditions, provided in another embodiment of this application.

[0026] Figure 9 This is a schematic diagram of the equivalent structure of a virtual network control device for a wind-storage aggregation system operating under weak network conditions, provided in another embodiment of this application. Detailed Implementation

[0027] To make the objectives and technical solutions of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the described embodiments of this application without creative effort are within the scope of protection of this application.

[0028] In one embodiment, see Figure 1This application provides a virtual network construction control method for a wind-storage aggregation system operating under weak network conditions. The virtual network construction control method for a wind-storage aggregation system operating under weak network conditions may include the following steps: steps S1 to S6.

[0029] Step S1: Obtain the grid connection point voltage vector, perform phase-locked loop processing on the grid connection point voltage vector, and obtain the grid connection point voltage phase.

[0030] Step S2: Generate a virtual voltage vector based on the virtual network control loop, subtract the virtual voltage vector from the grid connection point voltage vector, and obtain the virtual network current through the virtual impedance.

[0031] Step S3: Calculate the reference value of the d-axis base current of the inner current loop based on the deviation between the calculated value of the grid active power and the set value of the grid active power, and calculate the reference value of the q-axis base current of the inner current loop based on the deviation between the voltage vector at the grid connection point and the rated value of the AC voltage.

[0032] Step S4: Multiply the virtual network current by the gain coefficient to obtain the additional current reference value of the inner current loop, and superimpose it with the basic current reference value to generate a reference voltage through the inner current loop. After coordinate transformation, the reference voltage is sent to the PWM controller to obtain the PWM signal.

[0033] Step S5: Establish the small-signal differential equations of the entire control system. Based on the small-signal differential equations of the entire control system, construct the full-order state-space model of the wind turbine energy storage aggregation grid-connected system.

[0034] Step S6: Draw the eigenvalue trajectory of the state matrix based on the full-order state-space model of the wind turbine energy storage aggregation grid-connected system, and determine the range of gain coefficients based on the eigenvalue trajectory.

[0035] This application's virtual grid-building control method for wind-storage aggregation systems operating under weak grid conditions utilizes a phase-locked loop (PLL) to accurately acquire the grid connection point voltage phase. A virtual voltage vector is then generated using a virtual grid-building control loop, and the grid-building current is obtained through virtual impedance. This process simulates the physical characteristics of a synchronous generator, actively providing voltage and frequency support to the weak grid and enhancing the system's robustness. Through the coordination of grid-following control and an additional current reference, precise tracking and regulation of active power and voltage are achieved. The composite reference signal is then used to drive the converter via an inner current loop and PWM modulation, ensuring the speed and accuracy of control. A full-order state-space model of the wind turbine-storage aggregation grid-connected system is established, and the stability range of key gain coefficients is determined based on eigenvalue locus analysis. This method fully considers the impact of weak grid scenarios on the subsynchronous oscillation characteristics of grid-following wind turbines, improving the operational stability of wind-storage aggregation systems with DC-side energy storage assistance under weak grid conditions.

[0036] In step S1, please refer to Figure 1In step S1, the grid connection point voltage vector is obtained, and the grid connection point voltage vector is processed by a phase-locked loop to obtain the grid connection point voltage phase.

[0037] Specifically, please refer to Figure 2 The grid connection point voltage vector can be obtained through voltage sensors and sampling circuits. u t , grid connection point voltage vector u t The grid connection point voltage vector is transformed by coordinate transformation. u t Transforming from the three-phase stationary coordinate system abc to the two-phase rotating coordinate system dq, we obtain the d-axis component of the grid-connected point voltage. u td and the q-axis component of the grid connection point voltage u tq The q-axis component of the grid connection point voltage u tq Input the phase-locked loop (PLL) PI controller, and then compare the output value of the PLL PI controller with the rated angular frequency. ω n The angular frequency of the grid connection point voltage can be obtained by adding them together. ω The angular frequency of the grid connection point voltage ω Input phase-locked loop integral controller Obtain the phase of the grid connection point voltage θ .

[0038] As an example, the small-signal differential equation of a phase-locked loop is: in, This represents the disturbance in the output phase of the phase-locked loop. k pllp and k plli These are the proportional and integral coefficients of the phase-locked loop PI controller, respectively. This represents the disturbance of the q-axis component of the grid connection point voltage. This is the disturbance output of the phase-locked loop integral controller.

[0039] As an example, the voltage phase at the grid connection point θ This refers to the output phase of the phase-locked loop; it can be used to determine the phase of the grid connection point voltage. θ As a reference phase for coordinate transformation from a three-phase stationary coordinate system to a two-phase rotating coordinate system, it enables synchronization between the grid-side converter of the wind-storage aggregation system and the power grid.

[0040] As an example, the rated angular frequency ω n According to the rated frequency f n Setting, i.e., rated angular frequency ωn =2π f n .

[0041] As an example, the grid voltage is u g .

[0042] In step S2, please refer to Figure 1 In step S2, a virtual voltage vector is generated based on the virtual network control loop. The virtual voltage vector is then subtracted from the grid connection point voltage vector and passed through a virtual impedance to obtain the virtual network current.

[0043] For example, please refer to Figure 3 Step S2 may include the following steps: Step S21 to Step S24.

[0044] Step S21: Input the virtual network active power and the virtual network active power reference value into the active power loop to generate the phase of the virtual voltage vector.

[0045] Step S22: Input the virtual network reactive power and the virtual network reactive power reference value into the reactive power loop to generate the amplitude of the virtual voltage vector.

[0046] Step S23: Perform vector synthesis on the phase and magnitude of the virtual voltage vector to obtain the virtual voltage vector.

[0047] Step S24: Subtract the virtual voltage vector from the grid connection point voltage vector to obtain the voltage difference, and then use the voltage difference to obtain the virtual grid current through virtual impedance control.

[0048] Step S25: Calculate the virtual grid active power and reactive power using the grid connection point voltage vector and the virtual grid current. Regenerate the phase and amplitude of the new virtual voltage vector by passing the virtual grid active power and reactive power through the active power loop and reactive power loop. After multiple iterations, obtain the final virtual grid current.

[0049] Specifically, in step S21, please refer to Figure 2 The active power loop will virtualize the active power of the network. P v Reference value of active power in virtual network P vref After subtraction, the active power deviation of the virtual network is obtained. Active power deviation in virtual network go through After processing, it is then passed through a transfer function simulating the rotor motion of a synchronous machine. To suppress oscillations, the obtained output value is related to the rated angular frequency. ω n The virtual network voltage frequency is obtained by adding them together. ωv The virtual grid voltage frequency ω v Input active loop integral controller Obtain the virtual network voltage phase θ v ,in, J and D p These are virtual inertia and damping, respectively.

[0050] As an example, the reference value for active power in virtual network construction P vref It can be set according to project needs.

[0051] Further, in step S22, please refer to... Figure 2 The reactive power loop will virtualize the reactive power of the network. Q v Reactive power reference value of virtual network Q vref After subtraction, the reactive power deviation of the virtual network is obtained. The reactive power deviation of the virtual network go through The processed data is then input into the reactive power loop integral controller. The automatic voltage regulator, simulating a synchronous generator, compares the obtained output value with the rated voltage. U n The sum is used to obtain the virtual network voltage amplitude. E v ,in, K q This is the reactive power integral coefficient.

[0052] As an example, the small-signal differential equations for the active power loop and the reactive power loop are: in, This represents the disturbance to the voltage frequency of the virtual network. This represents the disturbance in the virtual grid voltage phase. This represents the disturbance to the voltage amplitude of the virtual network. J and D p These are virtual inertia and damping, respectively. ω n The rated angular frequency, K q The reactive power integral coefficient, u td0 The steady-state value of the d-axis component of the grid connection point voltage. This represents the disturbance of the d-axis component of the grid connection point voltage. This represents the disturbance of the q-axis component of the grid connection point voltage. ivd0 This represents the steady-state value of the d-axis component of the virtual network current. i vq0 This represents the steady-state value of the q-axis component of the virtual network current. This represents the disturbance of the d-axis component of the virtual network current. This represents the disturbance of the q-axis component of the virtual network current.

[0053] As an example, the reference value for reactive power in virtual network construction Q vref It can be set according to project needs; it can be set to zero.

[0054] Furthermore, in step S23, the virtual network voltage phase is... θ v and virtual network voltage amplitude E v Vector synthesis is performed to obtain the virtual voltage vector. u v .

[0055] Further, in step S24, the virtual voltage vector is... u v With grid connection point voltage vector u t The voltage difference is obtained by subtraction, and then the voltage difference is controlled by virtual impedance. Obtain virtual network current i v ,in, L v and R v These are virtual reactance and virtual resistance, respectively.

[0056] As an example, the small-signal differential equation for virtual impedance control is expressed by the following formula: in, L v and R v These are virtual reactance and virtual resistance, respectively. and These represent the disturbances to the d-axis and q-axis components of the virtual network current, respectively. This represents the disturbance in the virtual grid voltage phase. This represents the disturbance to the voltage amplitude of the virtual network. This represents the disturbance of the d-axis component of the grid connection point voltage. This represents the disturbance of the q-axis component of the grid connection point voltage. ω n The rated angular frequency, u n The rated AC voltage. This represents the disturbance in the output phase of the phase-locked loop.

[0057] Furthermore, in step S25, the grid connection point voltage vector is utilized. u t With virtual network current i v The active power of the virtual network is obtained through power calculation. P v and reactive power Q v The active power of virtual networking P v and reactive power Q v Respectively compared with the virtual network active power reference value P vref and virtual network reactive power reference value Q vref By re-inputting the active and reactive power loops, the phase and magnitude of a new virtual voltage vector are generated. After multiple iterations, the final virtual grid current is obtained. i v .

[0058] In step S3, please refer to Figure 1 In step S3, the reference value of the d-axis base current of the inner current loop is calculated based on the deviation between the calculated value of the grid active power and the set value of the grid active power, and the reference value of the q-axis base current of the inner current loop is calculated based on the deviation between the grid connection point voltage vector and the rated value of the AC voltage.

[0059] Specifically, please refer to Figure 2 Calculate the active power of the grid. P G With active power setpoint P Gref The deviation is input into the active power loop PI controller to obtain the reference value of the d-axis base current in the inner current loop. i dref .

[0060] As an example, the calculated value of active power in the grid P G It can be based on the grid connection point voltage vector u t The formula for setting the reference value of the inner current loop is: in, i dref and i qref These are the reference values ​​for the d-axis and q-axis base currents of the inner current loop, respectively. utd and u tq These are the d-axis and q-axis components of the grid connection point voltage, respectively.

[0061] Furthermore, the d-axis component of the grid connection point voltage is calculated. u td With AC voltage rating u n The deviation is input into the AC voltage loop PI controller to obtain the q-axis base current reference value of the inner current loop. i qref .

[0062] As an example, the d-axis base current reference value of the inner current loop i dref Reference value of q-axis base current in the inner current loop i qref Expressed as follows: in, k pcp and k pci These are the proportional and integral coefficients of the active power loop PI controller, respectively. k qcp and k qci These are the proportional and integral coefficients of the AC voltage loop PI controller, respectively. P Gref and P G These are the setpoint and calculated values ​​of the active power connected to the grid, respectively. u n and u td These represent the rated AC voltage and the d-axis components of the grid connection point voltage, respectively.

[0063] As an example, the d-axis base current reference value of the inner current loop i dref Reference value of q-axis base current in the inner current loop i qref These can be used as reference values ​​for the output current of the d-axis grid-side converter and the q-axis grid-side converter, respectively.

[0064] In step S4, please refer to Figure 1 In step S4, the virtual network current is multiplied by the gain coefficient and used as the additional current reference value of the inner current loop. This value is then superimposed on the basic current reference value to generate a reference voltage through the inner current loop. The reference voltage is then sent to the PWM controller after coordinate transformation to obtain the PWM signal.

[0065] For example, please refer to Figure 4 Step S4 may include the following steps: Step S41 to Step S46.

[0066] Step S41: Multiply the d-axis and q-axis components of the virtual network current by the gain coefficient to obtain the reference values ​​of the additional d-axis and q-axis components of the current inner loop.

[0067] Step S42: The additional current d-axis component reference value of the inner current loop, the basic current reference value of the inner current loop d-axis, and the output current d-axis component of the grid-side converter are fused together and the voltage signal d-axis component is generated by the first inner current loop PI controller; the additional current q-axis component reference value of the inner current loop, the basic current reference value of the inner current loop q-axis, and the output current q-axis component of the grid-side converter are fused together and the voltage signal q-axis component is generated by the second inner current loop PI controller.

[0068] Step S43: Multiply the d-axis component and q-axis component of the grid connection point voltage by the voltage feedforward coefficient to obtain the reference values ​​of the d-axis component and q-axis component of the feedforward voltage.

[0069] Step S44: The d-axis component of the grid-side converter output current and the q-axis component of the grid-side converter output current are coupled and compensated to obtain the d-axis component and the q-axis component of the feedforward voltage, respectively.

[0070] Step S45: Fuse the reference value of the d-axis component of the feedforward voltage, the d-axis component of the voltage signal, and the q-axis component of the feedforward voltage to obtain the reference voltage d-axis component; fuse the reference value of the q-axis component of the feedforward voltage, the q-axis component of the voltage signal, and the d-axis component of the feedforward voltage to obtain the reference voltage q-axis component.

[0071] Step S46: The d-axis component and q-axis component of the reference voltage are sent to the PWM controller after coordinate transformation to obtain the PWM signal.

[0072] Specifically, in step S41, please refer to Figure 2 The d-axis component of the virtual network current i vd Multiply by the gain factor k Obtain the reference value of the additional d-axis component of the current in the inner current loop. i vdref ,Right now ; The q-axis component of the virtual network current i vq Multiply by the gain factor k Obtain the reference value of the additional q-axis component of the current in the inner current loop. i vdqref ,Right now .

[0073] As an example, gain coefficient kIt can be the current gain coefficient.

[0074] Further, in step S42, the reference value of the additional current d-axis component of the inner current loop is... i vdref Reference value of the d-axis base current of the inner current loop i dref Superimposed and then combined with the d-axis component of the grid-side converter output current i d By performing a difference comparison, the error of the d-axis current component is obtained. ,Right now d-axis current component error The d-axis component of the voltage signal is generated by the first current inner loop PI controller.

[0075] Furthermore, the reference value of the additional q-axis component of the current in the inner current loop is... i vqref Reference value of q-axis base current in the inner current loop i qref Superimposed and then combined with the q-axis component of the grid-side converter output current i q By performing a difference comparison, the error of the q-axis current component is obtained. ,Right now q-axis current component error The q-axis component of the voltage signal is generated by the second current inner loop PI controller.

[0076] As an example, the proportional gain of the first current inner loop PI controller and the second current inner loop PI controller is: k cp The integral coefficient is k ci .

[0077] Further, in step S43, the d-axis component of the grid connection point voltage is... u td Multiply by voltage feedforward factor k VF Obtain the reference value of the d-axis component of the feedforward voltage. u tdref ,Right now ; q-axis component of grid connection point voltage u tq Multiply by voltage feedforward factor k VF The reference value of the q-axis component of the feedforward voltage is obtained. u tqref ,Right now .

[0078] As an example, the d-axis component of the grid connection point voltage... u td and q-axis componentsu tq Multiply by the voltage feedforward factor respectively k VF The process can be used as a voltage feedforward circuit.

[0079] Furthermore, in step S44, the d-axis component of the grid-side converter output current is... i d The d-axis component of the feedforward voltage is obtained after coupling compensation; the q-axis component of the grid-side converter output current is obtained. i q The q-axis component of the feedforward voltage is obtained after coupling compensation.

[0080] As an example, coupling compensation can be ,in, L f For machine-side filter inductance, ω ω is the angular frequency of the voltage at the grid connection point.

[0081] Further, in step S45, the d-axis component reference value of the feedforward voltage is... u tdref The reference voltage d-axis component is obtained by superimposing it with the d-axis component of the voltage signal and then subtracting it from the q-axis component of the feedforward voltage. .

[0082] Furthermore, the q-axis component reference value of the feedforward voltage is... u tqref The reference voltage q-axis component is obtained by superimposing it with the q-axis component of the voltage signal and then subtracting it from the d-axis component of the feedforward voltage. .

[0083] Further, in step S46, the d-axis component and q-axis component of the reference voltage are sent to the PWM controller after coordinate transformation to obtain the PWM signal, and the PWM signal is input to the grid-side converter to obtain the bridge arm voltage.

[0084] As an example, the small-signal differential equation of the inner current loop is expressed by the following formula: in, and These represent the disturbances to the d-axis and q-axis components of the reference voltage, respectively. k cp and k ci These are the proportional and integral coefficients of the current inner-loop PI controller, respectively. and These represent the disturbances in the d-axis and q-axis components of the grid-side converter output current, respectively. and These are the d-axis and q-axis disturbances output by the current loop integral controller, respectively. L f For machine-side filter inductance, k This is the gain coefficient. k VF For voltage feedforward coefficients, and These represent the disturbances to the d-axis and q-axis components of the virtual network current, respectively. This represents the disturbance of the d-axis component of the grid connection point voltage. This represents the disturbance of the q-axis component of the grid connection point voltage. ω n This is the rated angular frequency.

[0085] In step S5, please refer to Figure 1 In step S5, the small-signal differential equations of the entire control system are established, and the full-order state-space model of the wind turbine energy storage aggregation grid-connected system is constructed based on the small-signal differential equations of the entire control system.

[0086] Specifically, the small-signal differential equations of the phase-locked loop, the active and reactive power loops, the virtual impedance control, and the inner current loop are rearranged to obtain the small-signal differential equations of the entire control system. Based on the small-signal differential equations of the entire control system, a full-order state-space model of the wind turbine energy storage aggregation grid-connected system is constructed.

[0087] As an example, the expression for the small-signal differential equation of the entire control system is: in, and These represent the disturbances to the d-axis and q-axis components of the grid-side current, respectively. C f For filtering capacitors, L g For grid-side inductance, and These represent the disturbances to the d-axis and q-axis components of the reference voltage, respectively. This represents the disturbance of the d-axis component of the grid connection point voltage. This represents the disturbance of the q-axis component of the grid connection point voltage. ω n The rated angular frequency, and These represent the disturbances in the d-axis and q-axis components of the grid-side converter output current, respectively. L f This is the machine-side filter inductor.

[0088] As an example, the expression for the full-order state-space model of a wind turbine energy storage aggregation grid-connected system is as follows: in, A The state matrix, For the state variable matrix, This represents the disturbance in the virtual grid voltage phase. This represents the disturbance to the voltage frequency of the virtual network. This represents the disturbance to the voltage amplitude of the virtual network. and These represent the disturbances to the d-axis and q-axis components of the virtual network current, respectively. This represents the disturbance in the output phase of the phase-locked loop. This is the disturbance output of the phase-locked loop integral controller. and These are the d-axis and q-axis disturbances output by the current loop integral controller, respectively. and These represent the disturbances in the d-axis and q-axis components of the grid-side converter output current, respectively. This represents the disturbance of the d-axis component of the grid connection point voltage. This represents the disturbance of the q-axis component of the grid connection point voltage. and These represent the disturbances to the d-axis and q-axis components of the grid-side current, respectively.

[0089] As an example, the state matrix A The expression is: in, k pllp and k plli These are the proportional and integral coefficients of the phase-locked loop PI controller, respectively. J and D p These are virtual inertia and damping, respectively. ω n The rated angular frequency, u n The rated AC voltage. K q The reactive power integral coefficient, u td0 The steady-state value of the d-axis component of the grid connection point voltage. i vd0 This represents the steady-state value of the d-axis component of the virtual network current. i vq0 This represents the steady-state value of the q-axis component of the virtual network current. L v and R v These are virtual reactance and virtual resistance, respectively. k cp andk ci These are the proportional and integral coefficients of the current inner-loop PI controller, respectively. L f For machine-side filter inductance, C f For filtering capacitors, L g For grid-side inductance, k This is the gain coefficient. k VF This is the voltage feedforward coefficient.

[0090] In step S6, please refer to Figure 1 In step S6, the eigenvalue trajectory of the state matrix is ​​drawn based on the full-order state-space model of the wind turbine energy storage aggregation grid-connected system, and the range of gain coefficients is determined based on the eigenvalue trajectory.

[0091] Specifically, based on the full-order state-space model of the wind turbine energy storage aggregation grid-connected system, the eigenvalues ​​of the state matrix are determined, the eigenvalue trajectory of the state matrix is ​​plotted, the changes in the eigenvalue trajectory of the state matrix are observed when the grid strength and gain coefficient change, the impact on system stability is analyzed, and the range of gain coefficients suitable for the operation of the wind turbine energy storage aggregation grid-connected system under weak grid conditions is determined to improve the stability of the system operation under weak grid conditions.

[0092] In one embodiment, simulation experiments can be conducted to verify the effectiveness of the virtual grid construction control method proposed in this application for wind-storage aggregation systems operating under weak grid conditions. A grid-connected active power setpoint can be set. P Gref The reference value for active power in virtual network construction is 10kW. P vref 10kW, rated frequency f n 50Hz, AC voltage rated value u n 220V, machine-side filter inductor L f The filter capacitor has a current of 3.2mH. C f 10μF, virtual reactance L v The virtual resistance is 3mH. R v The voltage feedforward coefficient is 0.05Ω. k VF The value is 0.8. For specific simulation parameter settings, please refer to Table 1.

[0093] Table 1 Simulation Parameters In one example Figure 5Gain coefficient when short-circuit ratio changes k =0 and gain coefficient k Eigenvalue locus of the state matrix when λ = 0.5. From... Figure 5 It can be seen that when the short-circuit ratio (SCR) varies from 1.5 to 5, the gain coefficient... k When the gain coefficient is 0, the real parts of the eigenvalues ​​of the state matrix are all positive, and the system is unstable; when the gain coefficient is 0, the real parts of the eigenvalues ​​of the state matrix are all positive. k When λ = 0.5, the eigenvalues ​​of the state matrix are all to the left of the imaginary axis, indicating that the system is stable.

[0094] In yet another example, Figure 6 This is the eigenvalue locus of the state matrix as the gain coefficient changes. Figure 6 It can be seen that when the short-circuit ratio is 1.5, the gain coefficient... k When the state matrix changes from 0.02 to 1, the eigenvalues ​​of the state matrix initially have positive real parts, and when the gain coefficient... k When the value is greater than 0.1, the eigenvalues ​​of the state matrix are all to the left of the imaginary axis, therefore the gain coefficient... k It is advisable to choose a value between 0.1 and 1.

[0095] In yet another example, Figure 7 This is a power waveform diagram showing the control network type and the additional virtual network control when the short-circuit ratio changes abruptly. From... Figure 7 It can be seen that when the short-circuit ratio is 5, the output active power waveforms of the grid-following control (GFL) and the grid-following control with virtual grid construction control (GFL+VGFM) are basically identical. When the short-circuit ratio suddenly drops to 1.5, the output active power of the grid-following control method has excessive overshoot and gradually becomes unstable, while the output active power of the grid-following control with virtual grid construction control method has smaller oscillations and gradually stabilizes. In summary, the virtual grid construction control method of the wind-storage aggregation system applicable to weak grid operation proposed in this application can improve the operational stability of the wind-storage aggregation system using grid-following control in weak grid scenarios.

[0096] In the virtual grid-building control method for wind-storage aggregation systems operating under weak grid conditions, this application accurately obtains the voltage phase by inputting the grid connection point voltage vector into a phase-locked loop PI controller after coordinate transformation. A virtual voltage vector is generated through the virtual grid-building control loop, and the grid-building current is obtained through virtual impedance. Through iterative optimization of the active and reactive power loops, the physical characteristics of a synchronous generator can be simulated, automatically providing voltage and frequency support for the weak grid and solving the problem of insufficient support capacity in traditional grid-connected systems. By using the base reference value of the current inner loop, multiplying the virtual grid-building current by a gain coefficient as an additional reference, and superimposing it, and then driving the converter through the current inner loop and PWM modulation, precise tracking and regulation of active power and voltage can be achieved, ensuring control speed and accuracy. By establishing a full-order state-space model of the wind turbine-storage aggregation grid-connected system and plotting the characteristic root locus to determine the gain coefficient range, the risk of oscillation and instability can be theoretically avoided. In summary, the method proposed in this application can fully consider the impact of weak grid scenarios on the subsynchronous oscillation characteristics of grid-connected wind turbines, improve the operational stability of wind-storage aggregation systems based on DC-side energy storage assistance in weak grid scenarios, and virtually equivalently represent the parallel connection of grid-connected and grid-connected converters based on a single physical converter on the grid side of the wind-storage aggregation system. By controlling the converter to simulate virtual grid-connected current integration, the power characteristics of the converter at the grid connection point are improved. By optimizing the virtual grid-connected current gain, the operational stability of wind-storage aggregation systems using grid-connected control of traditional grid-side converters in weak grid scenarios is improved. This method has significant application value in the current new power systems with a high proportion of wind power integration.

[0097] It should be understood that although the steps in the flowcharts of the accompanying drawings are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some of the steps in the accompanying drawings may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the sub-steps or stages of other steps.

[0098] In another embodiment, please refer to Figure 8This application also provides a virtual network construction control device 1 for a wind-storage aggregation system operating under weak grid conditions. The virtual network construction control device 1 for a wind-storage aggregation system operating under weak grid conditions is connected to the power grid 2. The virtual network construction control device 1 for a wind-storage aggregation system operating under weak grid conditions may include a grid-connected converter module 11, a phase-locked loop module 12, a current inner loop module 13, a power loop module 14, a virtual network construction control loop module 15, a PWM modulation module 16, and a coordinate transformation module 17. The first end of the grid-connected converter module 11 is connected to the power grid 2. The second end of the grid-connected converter module 11 is connected to the first end of the PWM modulation module 16. The second end of the PWM modulation module 16 is connected to the first end of the current inner loop module 13. The third end of the grid-connected converter module 11 is connected to the first end of the phase-locked loop module 12. The second end of the phase-locked loop module 12 is connected to the coordinate transformation module 17. The second end of the current inner loop module 13 is connected to the power loop module 14. The third end of the current inner loop module 13 is connected to the virtual network construction control loop module 15.

[0099] As an example, the grid-connected converter module 11 is directly connected to the power grid 2, responsible for the transmission and exchange of actual power, and responds to the PWM signal generated by the PWM modulation module 16 to adjust the output voltage and current to maintain stable system operation.

[0100] As an example, the phase-locked loop module 12 is used to accurately obtain the phase information of the grid connection point voltage. By performing phase-locked processing on the grid connection point voltage vector, it outputs the grid connection point voltage phase signal to provide a synchronization reference for other modules, ensuring that the system is consistent with the grid frequency and phase.

[0101] As an example, the current inner loop module 13 receives reference values ​​of the d-axis current component and the q-axis current component of the current inner loop from the power loop module 14, as well as the virtual network current from the virtual network control loop module 15, and compares them with the actual feedback current. After passing through the PI controller and voltage feedforward coefficient, the reference voltage is obtained.

[0102] As an example, power loop module 14 is used to calculate values ​​based on grid active power. P G With active power setpoint P Gref The deviation, and the d-axis component of the grid connection point voltage. u td With AC voltage rating u n The deviation is calculated, and the reference values ​​of the d-axis current component and the q-axis current component of the inner current loop are calculated to achieve dual-loop control of active power and voltage.

[0103] As an example, the virtual grid control loop module 15 simulates the physical characteristics of a synchronous generator, generates a virtual voltage vector and a virtual grid current, and achieves active support for grid voltage and frequency through active and reactive power loop control, which can enhance the system's stability and anti-interference capability under weak grid conditions.

[0104] As an example, the PWM modulation module 16 receives the reference voltage in the rotating coordinate system output by the current inner loop module 13 and converts it back to the voltage signal in the stationary coordinate system through inverse coordinate transformation, generates a PWM signal, and outputs the PWM signal to the grid-connected converter module 11 to control the on and off timing of the switching devices inside the converter, so that the converter generates a bridge arm voltage that meets the reference voltage requirements, and finally realizes the precise grid-connected transmission of wind-storage energy to the grid.

[0105] As an example, the coordinate transformation module 17 transforms electrical quantities from the three-phase stationary coordinate system abc to the two-phase rotating coordinate system dq for control.

[0106] As an example, electrical quantities may include the grid-side converter output current. i Virtual network current i v Grid connection point voltage u t .

[0107] As an example, the reference phase of the coordinate transformation module 17 can be set as the output phase of the phase-locked loop module 12.

[0108] For example, please refer to Figure 9 , Figure 9 This is a schematic diagram of the equivalent structure of a virtual network control device for a wind-storage aggregation system operating under weak network conditions. To match the equivalent output impedance of the grid converter, The equivalent output impedance of the grid-type converter. V PCC This is the voltage at the point of common coupling (PCC), which is equal to the voltage at the grid connection point. V PCC = u t , U dc The DC-side voltage is supplied by the wind turbine or energy storage battery. Employing the proposed wind-storage aggregation system virtual grid control system, the actual output current of the grid-side converter comprises two parts: the reference current generated by the power outer loop of the traditional grid-connected control system. i dref Virtual network current generated by the virtual network control loop i vFrom the perspective of the grid side, the current injected into the grid is equivalent to two parallel converters that are controlled by grid-following and grid-building respectively. Therefore, the virtual grid-building control system of the wind-storage aggregation system can use a grid-following converter to simulate the output current dynamics of the grid-following converter and the grid-building converter connected in parallel. It can virtually achieve the effect of the grid-following converter and the grid-building converter connected in parallel based on a single physical converter on the grid side of the wind-storage aggregation system.

[0109] In the aforementioned virtual grid-building control device for wind-storage aggregation systems operating under weak grid conditions, the virtual grid-building control loop module provides inherent voltage and frequency support to the system by simulating the physical characteristics of a synchronous generator. This enhances the system's inertial damping characteristics, enabling the system to both track grid voltage like a grid-following device and actively stabilize the grid like a grid-building device, effectively suppressing voltage and frequency fluctuations at weak grid connection points. It improves the grid-connection robustness of wind-storage aggregation systems in low short-circuit capacity grids, suppresses broadband oscillation risks, and enhances the power quality and safe, stable operation of the regional grid through active voltage and frequency support. Furthermore, it effectively improves the voltage and frequency support capabilities and disturbance rejection performance of the system in weak grid scenarios, solving the problems of instability and insufficient support capabilities of traditional grid-following wind-storage systems in weak grids, and ensuring reliable grid-connected operation of wind-storage aggregation resources.

[0110] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0111] Although this application has been disclosed above with reference to embodiments, it is not intended to limit this application. Anyone skilled in the art can make some modifications and refinements without departing from the spirit and scope of this application.

Claims

1. A virtual network construction control method for wind-storage aggregation systems operating under weak network conditions, characterized in that, Includes the following steps: Obtain the grid connection point voltage vector, and perform phase-locked loop processing on the grid connection point voltage vector to obtain the grid connection point voltage phase; A virtual voltage vector is generated based on the virtual grid control loop. The virtual voltage vector is then subtracted from the grid connection point voltage vector and passed through a virtual impedance to obtain the virtual grid current. The reference value of the base current of the inner loop d-axis is calculated based on the deviation between the calculated value of the grid active power and the set value of the grid active power. The reference value of the base current of the inner loop q-axis is calculated based on the deviation between the grid connection point voltage vector and the rated value of the AC voltage. The virtual network current is multiplied by the gain coefficient and used as the additional current reference value of the inner current loop. This value is then superimposed on the basic current reference value to generate a reference voltage through the inner current loop. The reference voltage is then sent to the PWM controller after coordinate transformation to obtain the PWM signal. Establish the small-signal differential equations of the entire control system, and based on the small-signal differential equations of the entire control system, construct the full-order state-space model of the wind turbine energy storage aggregation grid-connected system. Based on the full-order state-space model of the wind turbine energy storage aggregation grid-connected system, the eigenvalue trajectory of the state matrix is ​​plotted, and the gain coefficient range is determined according to the eigenvalue trajectory.

2. The virtual network control method for wind-storage aggregation systems operating under weak network conditions according to claim 1, characterized in that, A virtual voltage vector is generated based on the virtual grid control loop. The virtual grid current is obtained by subtracting the virtual voltage vector from the grid connection point voltage vector and passing it through a virtual impedance. This includes: The virtual network active power and the virtual network active power reference value are input into the active power loop to generate the phase of the virtual voltage vector; The virtual network reactive power and the virtual network reactive power reference value are input into the reactive power loop to generate the amplitude of the virtual voltage vector. The phase and magnitude of the virtual voltage vector are vector-synthesized to obtain the virtual voltage vector. The voltage difference is obtained by subtracting the virtual voltage vector from the grid connection point voltage vector, and the virtual grid current is obtained by controlling the voltage difference through virtual impedance.

3. The virtual network control method for wind-storage aggregation systems operating under weak network conditions according to claim 2, characterized in that, The small-signal differential equations for the active and reactive power loops are: in, This represents the disturbance to the voltage frequency of the virtual network. This represents the disturbance in the virtual grid voltage phase. This represents the disturbance to the voltage amplitude of the virtual network. J and D p These are virtual inertia and damping, respectively. ω n The rated angular frequency, K q The reactive power integral coefficient, u td0 This represents the steady-state value of the d-axis component of the grid connection point voltage. This represents the disturbance of the d-axis component of the grid connection point voltage. This represents the disturbance of the q-axis component of the grid connection point voltage. i vd0 This represents the steady-state value of the d-axis component of the virtual network current. i vq0 This represents the steady-state value of the q-axis component of the virtual network current. This represents the disturbance of the d-axis component of the virtual network current. This represents the disturbance of the q-axis component of the virtual network current.

4. The virtual network construction control method for wind-storage aggregation systems operating under weak network conditions according to claim 2, characterized in that, The small-signal differential equation for virtual impedance control is expressed by the following formula: in, L v and R v These are virtual reactance and virtual resistance, respectively. and These represent the disturbances to the d-axis and q-axis components of the virtual network current, respectively. This represents the disturbance in the virtual grid voltage phase. This represents the disturbance to the voltage amplitude of the virtual network. This represents the disturbance of the d-axis component of the grid connection point voltage. This represents the disturbance of the q-axis component of the grid connection point voltage. ω n The rated angular frequency, u n The rated AC voltage. This represents the disturbance in the output phase of the phase-locked loop.

5. The virtual network control method for wind-storage aggregation systems operating under weak network conditions according to claim 1, characterized in that, Reference value of d-axis base current in the inner current loop i dref Reference value of q-axis base current in the inner current loop i qref Expressed as follows: in, k pcp and k pci These are the proportional and integral coefficients of the active power loop PI controller, respectively. k qcp and k qci These are the proportional and integral coefficients of the AC voltage loop PI controller, respectively. P Gref and P G These are the setpoint and calculated values ​​of the active power connected to the grid, respectively. u n and u td These represent the rated AC voltage and the d-axis components of the grid connection point voltage, respectively.

6. The virtual network construction control method for wind-storage aggregation systems operating under weak network conditions according to claim 1, characterized in that, The virtual network current is multiplied by a gain coefficient to obtain an additional current reference value for the inner current loop. This additional current reference value is then superimposed on the base current reference value to generate a reference voltage through the inner current loop. This reference voltage is then transformed by coordinates and sent to the PWM controller to obtain a PWM signal, including: Multiply the d-axis and q-axis components of the virtual network current by the gain coefficient to obtain the reference values ​​of the additional d-axis and q-axis components of the current inner loop. The additional current d-axis component reference value, the current inner loop d-axis base current reference value, and the grid-side converter output current d-axis component of the current inner loop are fused together and then used to generate a voltage signal d-axis component through a first current inner loop PI controller; the additional current q-axis component reference value, the current inner loop q-axis base current reference value, and the grid-side converter output current q-axis component of the current inner loop are fused together and then used to generate a voltage signal q-axis component through a second current inner loop PI controller. Multiply the d-axis and q-axis components of the grid connection point voltage by the voltage feedforward coefficient to obtain the reference values ​​of the d-axis and q-axis components of the feedforward voltage. The d-axis component of the grid-side converter output current and the q-axis component of the grid-side converter output current are respectively coupled and compensated to obtain the d-axis component and the q-axis component of the feedforward voltage. The reference value of the d-axis component of the feedforward voltage, the d-axis component of the voltage signal, and the q-axis component of the feedforward voltage are fused to obtain the reference voltage d-axis component; the reference value of the q-axis component of the feedforward voltage, the q-axis component of the voltage signal, and the d-axis component of the feedforward voltage are fused to obtain the reference voltage q-axis component. The d-axis component and q-axis component of the reference voltage are sent to the PWM controller after coordinate transformation to obtain the PWM signal.

7. The virtual network control method for wind-storage aggregation systems operating under weak network conditions according to claim 1, characterized in that, The small-signal differential equations of the entire control system include the small-signal differential equations of the phase-locked loop, the active power loop and the reactive power loop, the small-signal differential equations of the virtual impedance control, and the small-signal differential equations of the inner current loop. The expression of the small-signal differential equations of the entire control system is as follows: in, and These represent the disturbances to the d-axis and q-axis components of the grid-side current, respectively. C f For filtering capacitors, L g For grid-side inductance, and These represent the disturbances to the d-axis and q-axis components of the reference voltage, respectively. This represents the disturbance of the d-axis component of the grid connection point voltage. This represents the disturbance of the q-axis component of the grid connection point voltage. ω n The rated angular frequency, and These represent the disturbances in the d-axis and q-axis components of the grid-side converter output current, respectively. L f This is the machine-side filter inductor.

8. The virtual network control method for wind-storage aggregation systems operating under weak network conditions according to claim 1, characterized in that, The expression for the full-order state-space model of the wind turbine energy storage aggregation grid-connected system is as follows: in, A The state matrix, For the state variable matrix, This represents the disturbance in the virtual grid voltage phase. This represents the disturbance to the voltage frequency of the virtual network. This represents the disturbance to the voltage amplitude of the virtual network. and These represent the disturbances to the d-axis and q-axis components of the virtual network current, respectively. This represents the disturbance in the output phase of the phase-locked loop. This is the disturbance output of the phase-locked loop integral controller. and These are the d-axis and q-axis disturbances output by the current loop integral controller, respectively. and These represent the disturbances in the d-axis and q-axis components of the grid-side converter output current, respectively. This represents the disturbance of the d-axis component of the grid connection point voltage. This represents the disturbance of the q-axis component of the grid connection point voltage. and These represent the disturbances to the d-axis and q-axis components of the grid-side current, respectively.

9. The virtual network control method for wind-storage aggregation systems operating under weak network conditions according to claim 1, characterized in that, Based on the full-order state-space model of the wind turbine energy storage aggregation grid-connected system, the eigenvalue trajectory of the state matrix is ​​plotted, and the gain coefficient range is determined according to the eigenvalue trajectory. This includes determining the eigenvalues ​​of the state matrix based on the full-order state-space model of the wind turbine energy storage aggregation grid-connected system, plotting the eigenvalue trajectory of the state matrix, observing the changes in the eigenvalue trajectory of the state matrix when the grid strength changes and the gain coefficient changes, analyzing the impact on system stability, and determining the gain coefficient range suitable for the operation of the wind turbine energy storage aggregation grid-connected system under weak grid conditions.

10. A virtual network control device for wind-storage aggregation systems operating under weak network conditions, characterized in that, A virtual grid construction control method for a wind-storage aggregation system operating under weak grid conditions, as described in any one of claims 1 to 9, is used to execute the virtual grid construction control device for the wind-storage aggregation system operating under weak grid conditions, which is connected to the power grid. The virtual grid construction control device for the wind-storage aggregation system operating under weak grid conditions includes a grid-connected converter module, a phase-locked loop (PLL) module, a current inner loop module, a power loop module, a virtual grid construction control loop module, a PWM modulation module, and a coordinate transformation module. The first end of the grid-connected converter module is connected to the power grid. The second end of the grid-connected converter module is connected to the first end of the PWM modulation module. The second end of the PWM modulation module is connected to the first end of the current inner loop module. The third end of the grid-connected converter module is connected to the first end of the PLL module. The second end of the PLL module is connected to the coordinate transformation module. The second end of the current inner loop module is connected to the power loop module. The third end of the current inner loop module is connected to the virtual grid construction control loop module.

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