Power equivalent energy storage type doubly-fed fan double virtual synchronous machine control method and system

Abstract

The application belongs to the technical field of wind power generation control, and particularly relates to a power equivalent energy storage type double-fed fan double-virtual synchronous machine control method and system. According to a scheduling instruction or a preset condition, the method determines a unit equivalent inertia target and a unit primary frequency droop coefficient. Through rotor speed, energy storage state of charge, current active power of a grid-side converter and grid-side converter power, the inertia support bearing amount of a stator channel and a grid-side converter channel and the primary frequency droop coefficient distribution proportion are determined, and the unit equivalent inertia target is decomposed into respective equivalent inertia targets of the two channels. The power response equivalent method is used to determine the stator channel virtual synchronous machine control parameter and the grid-side converter channel virtual synchronous machine control parameter, and the rotor-side converter and the grid-side converter are controlled accordingly. The stability and controllability of the active power response of the wind turbine during the frequency support period under different operating conditions can be improved.

Description

Technical Field

[0001] This invention belongs to the field of wind power generation control technology, specifically a power-equivalent energy storage type doubly fed wind turbine dual virtual synchronous machine control method and system. Background Technology

[0002] The statements in this section merely refer to the background art related to this invention and do not necessarily constitute prior art.

[0003] Doubly fed wind turbines are wind turbine generators whose stator windings are connected to the grid, and whose rotor windings are connected to the grid through a converter. The electrical energy generated by this type of wind turbine can be fed into the grid through two channels: the stator windings and the back-to-back converter, hence the name "doubly fed".

[0004] Energy storage type doubly fed wind turbines are wind turbines with energy storage units (such as supercapacitors) added to the DC bus side of the above-mentioned units. This enables the grid-side converter, which is originally mainly used to maintain DC voltage stability, to have independent and controllable active power regulation capabilities. This forms two independent frequency support channels: the stator channel and the grid-side converter channel, providing greater flexibility and controllability for wind turbines to participate in grid frequency support.

[0005] The active power output of this type of wind turbine is mainly determined by the control system, lacking the inherent frequency response characteristics of a synchronous generator, and thus cannot spontaneously respond to system frequency changes like traditional synchronous turbines. To improve the frequency support capability of wind turbines, virtual synchronous generator (VSG) control technology has been introduced. By simulating the inertia, damping, and speed regulation characteristics of a synchronous generator, the wind turbine can possess inertial response and primary frequency regulation capabilities.

[0006] However, in the existing VSG control equations, there is no clear correspondence between the virtual inertia parameters and virtual damping parameters and the actual inertia-supported power response of the wind turbine. Specifically, the closed-loop active power response of the VSG is affected by the virtual inertia parameters, virtual damping parameters, and operating conditions, and its dynamic behavior is not equivalent to an ideal pure inertia element. Therefore, if the VSG control parameters are set directly based on the equivalent inertia target, it is difficult to ensure that the actual inertia-supported power response of the wind turbine is consistent with the target inertia-supported power response, which may lead to the frequency support effect deviating from expectations. At the same time, the frequency support capability of energy storage-type doubly-fed induction generator (DFIG) wind turbines is also affected by operating conditions such as rotor speed, energy storage state of charge, and grid-side converter power margin. Without a dual-channel coordinated allocation mechanism oriented towards the overall frequency support target of the unit, it is difficult to provide stable and controllable frequency support under different operating conditions. Summary of the Invention

[0007] This invention provides a power-equivalent energy storage type doubly fed wind turbine dual virtual synchronous machine control method and system, which solves the technical problem that the active power response of the energy storage type doubly fed wind turbine is difficult to accurately match the target and maintain stable and controllable operation during the frequency support period under a wide range of operating conditions.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: The first aspect of this invention discloses a power-equivalent energy storage type doubly-fed wind turbine dual virtual synchronous machine control method, comprising the following steps: Based on dispatch instructions or preset conditions, determine the unit equivalent inertia target and the unit primary frequency regulation droop coefficient of the energy storage type doubly fed wind turbine. Based on the current operating parameters of the wind turbine, determine the inertia support borne by the stator channel and the grid-side converter channel, as well as the allocation ratio of the primary frequency regulation droop coefficient. Based on the inertia support borne by the wind turbine, decompose the equivalent inertia target of the turbine into the equivalent inertia target of the stator channel and the equivalent inertia target of the grid-side converter channel. Using the power response equivalent method, the control parameters of the stator channel virtual synchronous machine and the grid-side converter channel virtual synchronous machine are determined according to the equivalent inertia target of the stator channel and the equivalent inertia target of the grid-side converter channel, respectively. The control parameters of the stator channel virtual synchronous machine are used to control the rotor-side converter, and the control parameters of the grid-side converter channel virtual synchronous machine are used to control the grid-side converter. The power response equivalence method involves minimizing the comprehensive error between the virtual synchronous machine's closed-loop power response and the target inertia-supported power response to obtain the control parameters of the virtual synchronous machine. Furthermore, the operating state parameters include at least the rotor speed, energy storage state of charge, current active power of the grid-side converter, and the upper limit of the grid-side converter's power.

[0009] Furthermore, the comprehensive error in the power response equivalence method is specifically as follows: ; in, , and The relative error of the slope for increasing power respectively Relative error of power integral and normalized power error The weighting coefficients.

[0010] Furthermore, the relative error of the initial power increase slope is as follows: ; The relative error of power integral during inertia support is as follows: ; Normalized power error, specifically: ; in, and The power increase rates of the target inertia-supported power response and the virtual synchronous machine closed-loop power response are respectively characterized in the early stage of frequency disturbance; and The cumulative energy of the target inertia-supported power response and the virtual synchronous machine closed-loop power response during the inertia support period is represented, respectively. Power response to target inertia Power response to support the inertia of the virtual synchronous machine.

[0011] Furthermore, the power increase rate of the target inertia-supported power response and the virtual synchronous machine closed-loop power response in the initial stage of frequency disturbance. and Specifically: ; ; The cumulative energy of the target inertia-supported power response and the virtual synchronous machine closed-loop power response during the inertia support period. and Specifically: ; ; in, Power response to target inertia Power response to support the inertia of the virtual synchronous machine. The time when the frequency disturbance occurs. This is the initial evaluation period. This is the termination time for the inertial response evaluation.

[0012] Furthermore, the power response equivalent method also includes setting boundary constraints on the control parameters of the virtual synchronous machine, and solving for the control parameters that minimize the comprehensive error under the boundary constraints, as shown in the following equation: ; in, , , and For the control parameter boundaries of the virtual synchronizer; The damping ratio of the dominant oscillation mode in the active response of the virtual synchronous machine. Its lower limit; For a given equivalent inertia target The minimum overall error.

[0013] Furthermore, based on the current operating parameters of the wind turbine, the inertia support load and primary frequency regulation droop coefficient allocation ratio between the stator channel and the grid-side converter channel are determined, including: Determine the rotor kinetic energy reserve coefficient based on the rotor speed: ; Determine the available state factor of DC energy storage based on the energy storage state of charge: ; The power adjustment margin factor for the grid-side converter is determined based on the current active power of the grid-side converter and the upper limit of the grid-side converter's power: ; The frequency support availability factor of the grid-side converter is determined based on the DC energy storage availability state factor and the grid-side converter power upshortage margin factor: ; in, The rotor's mechanical angular velocity before frequency disturbance. Minimum permissible speed, For the rated speed, This is the pre-charged state before frequency perturbation. The minimum permissible state of charge, For reference state of charge; This is the upper limit of the grid-side converter power. The active power of the grid-side converter before frequency disturbance.

[0014] Furthermore, determining the inertia support load and primary frequency regulation droop coefficient allocation ratio between the stator channel and the grid-side converter channel based on the current operating parameters of the wind turbine also includes: The inertia support factor of the grid-side converter channel is determined based on the frequency support availability factor of the grid-side converter. Further determine the equivalent inertia components of the grid-side converter channel. Equivalent inertia components of stator channel Specifically: ; ; ; in, The target is the equivalent inertia of the generator unit. and These represent the maximum achievable equivalent inertia components of the stator channel and the grid-side converter channel, respectively, under the unit power baseline value. During the above inertia target decomposition process, when the unit's equivalent inertia target exceeds the sum of the maximum achievable equivalent inertia components of the stator channel and the grid-side converter channel, the sum of these two components is taken as the actually achievable unit equivalent inertia.

[0015] Furthermore, the inertia support coefficient of the grid-side converter channel. It is also used to determine the primary frequency regulation droop coefficient allocation ratio between the stator channel and the grid-side converter channel, so that the droop coefficients of the stator channel and the grid-side converter channel are allocated according to the inertia support bearing ratio, as shown in the following formula: ; ; in, and These are the droop coefficient allocation ratios for the stator channel and the grid-side converter channel, respectively. This is the total droop coefficient of the unit. and These are the droop coefficients for the stator channel and the grid-side converter channel, respectively.

[0016] A second aspect of the present invention discloses a power-equivalent energy storage type doubly-fed wind turbine dual virtual synchronous machine control system, comprising: The target setting module is configured to determine the unit equivalent inertia target and the unit primary frequency regulation droop coefficient of the energy storage type doubly fed wind turbine according to the scheduling instructions or preset conditions. The allocation module is configured to: determine the inertia support load and primary frequency regulation droop coefficient allocation ratio of the stator channel and the grid-side converter channel based on the current operating status parameters of the wind turbine, and decompose the equivalent inertia target of the unit into the equivalent inertia target of the stator channel and the equivalent inertia target of the grid-side converter channel based on the inertia support load; The parameter configuration and control execution module is configured to: use the power response equivalent method to determine the stator channel virtual synchronous machine control parameters and the grid-side converter channel virtual synchronous machine control parameters according to the stator channel equivalent inertia target and the grid-side converter channel equivalent inertia target, respectively; wherein, the stator channel virtual synchronous machine control parameters are used to control the rotor-side converter, and the grid-side converter channel virtual synchronous machine control parameters are used to control the grid-side converter.

[0017] Compared with existing technologies, one or more of the above technical solutions have the following beneficial effects: By collecting measurable operating parameters such as wind turbine rotor speed, energy storage state of charge, and grid-side converter power margin, the inertia support responsibilities and primary frequency regulation droop coefficient allocation ratio of the stator channel and grid-side converter channel are dynamically determined. The equivalent inertia target of the unit is decomposed into the equivalent inertia targets of each of the two channels. Based on this, with the goal of minimizing the comprehensive error between the closed-loop power response of the virtual synchronous machine and the target inertia support power response, a quantitative mapping relationship between the equivalent inertia target and VSG control parameters is established. This enables the actual power response of the virtual synchronous machine to accurately match the target inertia support power response, thereby improving the stability and controllability of the active power response of the wind turbine during frequency support under different speeds, energy storage state of charge, and grid-side converter power margin conditions. Attached Figure Description

[0018] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0019] Figure 1 A schematic diagram of a control system for an energy storage doubly fed wind turbine generator set provided in one or more embodiments of the present invention; Figure 2 The diagram illustrates the equivalent power response of a virtual synchronous machine under different equivalent inertia targets provided in one or more embodiments of the present invention; wherein: (a) power change curve with time when H=1.2s; (b) power change curve with time when H=3s; (c) power change curve with time when H=5s; Figure 3 This is a schematic diagram of equivalent power response error analysis provided by one or more embodiments of the present invention; wherein: (a) is The time-comprehensive error function value is at (a) Schematic diagram of the distribution on the plane; (b) Schematic diagram of the error index changes under different equivalent inertia targets; Figure 4 This is a schematic diagram illustrating the relationship between the equivalent inertia target and the virtual synchronizer parameter configuration provided in one or more embodiments of the present invention; wherein: (a) represents the optimal inertia parameters. With equivalent inertia target (a) shows the changing curve; (b) shows the damping parameters. With equivalent inertia target A graph showing the changes; Figure 5 This is a schematic diagram of the equivalent inertia allocation results of dual virtual synchronous machines under different operating states provided by one or more embodiments of the present invention; wherein: (a) is the inertia borne by the grid-side converter. (a) Schematic diagram showing the changes in energy storage state of charge and wind turbine speed; (b) shows the inertia borne by the stator side. A schematic diagram showing the changes in energy storage state of charge and wind turbine speed; (c) shows the achievable inertia of the unit. A schematic diagram showing the changes in energy storage state of charge and wind turbine speed; Figure 6 A schematic diagram of the frequency support control structure of the dual virtual synchronous machine for an energy storage doubly fed wind turbine provided in one or more embodiments of the present invention; Figure 7 This is a schematic diagram illustrating the operation results under wind speed fluctuation and energy storage charging conditions provided by one or more embodiments of the present invention; wherein: (a) is the wind speed v w (a) Curves showing the change over time; (b) Rotor angular velocity. ω r (c) shows the stator current as a function of time. i s The graph shows the change over time; (d) represents the rotor current. i r (e) is a graph showing the change over time; stator power is also shown. P s The graph shows the change over time; (f) represents the energy storage power. P es A graph showing the change over time; (g) represents the power of the grid-side converter. P gsc A graph showing the change over time; (h) represents the unit power. P wt The graphs show the changes over time; (i) is the graph showing the change in the state of charge of the energy storage over time; (j) is the graph showing the DC side voltage. u dc A graph showing how the graph changes over time; Figure 8 This is a schematic diagram of the equivalent verification results of the inertia-supported power response provided by one or more embodiments of the present invention; wherein: (a) is the grid frequency. f g (a) Curve showing the change over time; (b) shows the stator power. P s (c) is a graph showing the power of the grid-side converter over time. P gsc A graph showing the change over time; (d) represents the unit power. P wt (e) is a graph showing the change over time; the remaining power of the unit is shown in Figure 1. ΔP wt A graph showing the change in target inertia support power response over time; Figure 9 This is a schematic diagram illustrating the verification results of the dual virtual synchronous machine cooperative frequency support power response provided in one or more embodiments of the present invention, wherein (a) is the grid frequency.f g (a) Curve showing the change over time; (b) shows the stator power. P s (c) is a graph showing the power of the grid-side converter over time. P gsc A graph showing the change over time; (d) represents the unit power. P wt (e) is a graph showing the change over time; the remaining power of the unit is shown in Figure 1. ΔP wt A graph showing the change over time; (f) represents the rotor angular velocity. ω r (g) is a graph showing the change over time; the graph shows the change of the state of charge of the energy storage over time. Figure 10 This is a schematic diagram showing the comparison results of system frequency response provided in one or more embodiments of the present invention. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0021] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0022] When energy storage-type doubly-fed wind turbines participate in grid frequency support, there is a problem that the active power response of the unit fluctuates with the changes in operating conditions during the frequency support period, resulting in insufficient stability and controllability of frequency support.

[0023] First, at the parameter configuration level, existing VSG control methods lack a mapping between the equivalent inertia target and the VSG control parameters. Although the VSG's active power outer loop is constructed based on the virtual rotor motion equations, its closed-loop power response is affected by the virtual inertia parameters, virtual damping parameters, and operating conditions, resulting in dynamic characteristics that are not ideal for an inertia-based system. Therefore, directly setting the VSG virtual inertia parameters based on the equivalent inertia target makes it difficult to guarantee that the actual inertia-supported power response matches the target inertia-supported power response. This is one of the key technical issues affecting the stability and controllability of frequency support.

[0024] Secondly, at the system architecture level, the energy storage-type doubly-fed induction generator (DFIG) wind turbine includes two independent frequency support channels: a stator channel and a grid-side converter channel. These channels provide support power by releasing rotor kinetic energy and utilizing DC energy storage, respectively. The power response characteristics of the two channels differ, and each is constrained by operating conditions such as rotational speed, energy storage state of charge, and power margin. If the allocation of support tasks between the two channels cannot be dynamically coordinated based on real-time conditions, the unit's active power response during frequency support will fluctuate with changes in operating conditions. This is another key technical issue affecting the stability and controllability of frequency support under a wide range of operating conditions.

[0025] In summary, this solution addresses the technical challenge of accurately matching the active power response of energy storage-type doubly-fed induction generator (DFIG) wind turbines to the target and maintaining stable controllability during the frequency support period under a wide range of operating conditions. Specifically, existing VSG control methods lack a clear correspondence between the equivalent inertia target and the VSG control parameters, making it difficult for the actual power response to match the target power response during the inertia support phase. Furthermore, the frequency support capability of the stator channel and the grid-side converter channel is affected by rotor speed, energy storage state of charge, and grid-side converter power margin, making it difficult to coordinate the allocation of inertia support and primary frequency regulation load according to operating conditions. This invention determines the VSG control parameters through an equivalent power response method during the frequency support period and allocates the inertia support and primary frequency regulation load of the stator channel and the grid-side converter channel according to the operating conditions, thereby improving the stability and controllability of the active power response during the frequency support period under a wide range of operating conditions.

[0026] Therefore, this solution provides a power-equivalent energy storage type doubly-fed induction generator (DFIG) dual virtual synchronous machine control method and system. Taking the target inertia-supported power response as the benchmark, the VSG control parameter configuration is transformed into a power response consistency optimization problem, and a quantitative mapping relationship between the equivalent inertia target and the VSG control parameters is established. By comprehensively considering the rotor speed, energy storage state of charge, and grid-side converter power up-adjustment margin, the inertia support borne by the stator channel and the grid-side converter channel and the allocation ratio of the primary frequency regulation droop coefficient are coordinated to achieve stable and controllable active power response of the unit during the frequency support period under wide operating conditions.

[0027] A power-equivalent energy storage type doubly-fed wind turbine dual-virtual synchronous machine control method includes the following steps: Based on dispatch instructions or preset conditions, determine the unit equivalent inertia target and the unit primary frequency regulation droop coefficient of the energy storage type doubly fed wind turbine. Based on the current operating parameters of the wind turbine, determine the inertia support borne by the stator channel and the grid-side converter channel, as well as the allocation ratio of the primary frequency regulation droop coefficient. Based on the inertia support borne by the wind turbine, decompose the equivalent inertia target of the turbine into the equivalent inertia target of the stator channel and the equivalent inertia target of the grid-side converter channel. Using the power response equivalent method, the control parameters of the stator channel virtual synchronous machine and the grid-side converter channel virtual synchronous machine are determined according to the equivalent inertia target of the stator channel and the equivalent inertia target of the grid-side converter channel, respectively. The control parameters of the stator channel virtual synchronous machine are used to control the rotor-side converter, and the control parameters of the grid-side converter channel virtual synchronous machine are used to control the grid-side converter. The power response equivalence method is as follows: the control parameters of the virtual synchronous machine are obtained by minimizing the comprehensive error between the closed-loop power response of the virtual synchronous machine and the power response of the target inertia support.

[0028] This scheme establishes a dual virtual synchronous machine frequency support power response model for the stator channel and grid-side converter channel of an energy storage-type doubly-fed induction generator (DFIG) wind turbine. This model describes the relationship between frequency disturbances and the power responses of the two channels, and is used to characterize the active power response during wind turbine-level frequency support.

[0029] By using the power response equivalence method, a quantitative mapping relationship between the equivalent inertia target and the VSG control parameters was established, enabling the actual power response of the VSG to accurately match the target inertia support power response, thus solving the technical problem that the equivalent inertia target is difficult to be directly configured as the VSG control parameters.

[0030] By linking the frequency support target of the wind turbine unit with the support contribution of the stator channel and the grid-side converter channel, the frequency support tasks of the stator channel and the grid-side converter channel are coordinated and allocated, so that the unit can maintain stable and controllable frequency support performance under different rotor speeds, energy storage state of charge and grid-side converter power margins, thus solving the problem of coordinated allocation between the two channels.

[0031] By combining the power response equivalence method with dual-channel coordinated allocation, the wind turbine can maintain the stability and controllability of the active power response during the frequency support period even when the rotor speed, energy storage state of charge, and grid-side converter power margin change, thus achieving stable and controllable frequency support under a wide range of operating conditions.

[0032] The specific process of this scheme will be described in detail below with reference to the attached diagram.

[0033] 1. Frequency support modeling of dual virtual synchronous machines for energy storage type doubly fed wind turbine units.

[0034] Energy storage-type doubly-fed induction generators (DFIGs) extend the active power control degrees of freedom of the grid-side converter through DC-side energy storage, expanding the control objective of the grid-side converter from simply maintaining DC voltage stability to active power control with frequency support capabilities. Based on this structure, the dual virtual synchronous machine control of the rotor-side converter and the grid-side converter enables the stator-side active power and the grid-connected power of the grid-side converter to respond simultaneously to system frequency disturbances, thereby improving the overall equivalent inertia of the unit and its primary frequency regulation support capability.

[0035] 1.1 Topology and power coupling characteristics of energy storage type doubly fed wind turbine.

[0036] The structure of the energy storage type doubly fed wind turbine and its control system is as follows: Figure 1 As shown, the energy storage system (supercapacitor energy storage unit) is connected to the DC bus of a back-to-back converter via a bidirectional DC / DC converter. Specifically: the stator of the energy storage-type doubly-fed wind turbine is directly connected to the grid, and the rotor is connected to the grid through a converter (rotor-side converter). The rotor-side converter and the grid-side converter are connected back-to-back. The DC bus is connected between the rotor-side converter and the grid-side converter. The energy storage system (supercapacitor + bidirectional DC / DC converter) is connected to the DC bus. The bidirectional DC / DC converter controls the current to flow from the supercapacitor to the DC bus (discharging) or from the DC bus to the supercapacitor (charging).

[0037] In the above system, the power balance relationship of the converter DC bus is as follows: (1) In the formula, and These are the DC bus capacitance and DC voltage, respectively. The power injected into the DC bus by the rotor via the rotor-side converter. The power absorbed by the energy storage unit from the DC bus. This refers to the active power output from the grid-side converter to the power grid.

[0038] When the DC voltage is stable, equation (1) can be simplified to: (2) This formula shows that the energy storage unit bears the difference between the grid-connected power and the rotor power of the grid-side converter, thereby supporting independent power control of the grid-side converter under stable DC voltage conditions.

[0039] The unit's output power is: (3) In the formula, This refers to the active power output by the generating unit to the power grid. This refers to the active power output from the stator to the grid. During frequency support operation, the stator channel adjusts the electromagnetic torque and releases rotor kinetic energy through the rotor-side converter to output frequency-modulated power, while the grid-side converter channel outputs frequency-modulated power by calling upon DC energy storage. Together, they constitute the overall frequency support output of the unit.

[0040] Neglecting losses, stator and rotor power and slip satisfy: (4) Substituting equation (4) into equation (2), we get: (5) Therefore, the power of energy storage type doubly fed generator units The control is reflected in the coordination between stator power, grid-side converter power and energy storage power.

[0041] 1.2 Control strategy for dual virtual synchronous machines of rotor-side converter / grid-side converter.

[0042] To accommodate the independently adjustable stator-side active power and grid-connected power of energy storage-type doubly-fed induction generator (DFIG) wind turbines, a dual virtual synchronous machine control system is adopted for both the rotor-side and grid-side converters. This system provides inertia support and frequency regulation for both the stator and grid-side converter channels. The stator channel virtual synchronous machine controls the stator active power through the rotor-side converter, while the grid-side converter channel virtual synchronous machine controls the grid-side converter active power. Both virtual synchronous machines use a unified power outer loop configuration. Considering the differences in electromagnetic channels and power references between the stator and grid-side converter channels, the virtual synchronous machine parameters need to be configured separately.

[0043] In the power outer loop, the active power loop generates virtual angular frequency and phase angle based on the virtual rotor motion equation, while the reactive power loop generates virtual internal potential amplitude based on reactive power deviation. This forms a virtual internal potential, used to characterize the internal voltage characteristics of the equivalent synchronous machine. The main difference between the two control sides lies in the use of dq coordinate transformation angles oriented by the virtual internal potential. The grid-side converter channel virtual synchronous machine utilizes the virtual internal potential phase angle, while the stator channel virtual synchronous machine uses the slip angle, which is the sum of the virtual internal potential phase angle and the rotor electrical angle.

[0044] The active power outer loop of the virtual synchronous machine strategy is constructed based on the virtual rotor motion equation: (6) (7) In the formula, and These are virtual inertia parameters and virtual damping parameters, respectively. and These are the virtual angular frequency and phase angle of the virtual synchronizer, respectively. The angular frequency of the power grid. and These are the active power command and actual active power for the corresponding channel, respectively. When used in a stator channel virtual synchronizer, Parameter correspondence When used as a virtual synchronous machine for grid-side converter channels, Parameter correspondence . That is, These are the inertia parameters and damping parameters of the stator channel virtual synchronous machine, respectively, and the corresponding active response object is the stator active power. These are the inertia and damping parameters of the virtual synchronous machine for the grid-side converter channel, respectively. The corresponding active power response object is the grid-connected active power of the grid-side converter. The reactive power loop of the virtual synchronous machine strategy can be represented as: (8) In the formula, The virtual internal potential amplitude of the virtual synchronizer. For the transfer function of the reactive PI controller, and These are the reactive power command and the actual reactive power for the corresponding channel, respectively.

[0045] To analyze the relationship between the equivalent inertia of a virtual synchronous machine and its frequency-supported power response, the power angle is defined as follows: (9) In the formula, This represents the phase angle of the grid voltage.

[0046] The active and reactive power of a virtual synchronous machine can be expressed as: (10) In the formula, The voltage amplitude of the power grid. This represents the equivalent reactance between the virtual internal potential and the power grid. For a stator-channel virtual synchronizer, For stator reactance For the virtual synchronous machine of the grid-side converter channel, For filter reactance .

[0047] At the work site ( , Linearization around ) yields: (11) in, , , The subscript 0 indicates the steady-state operating point value of the corresponding variable, and Δ indicates the small-signal increment of the corresponding variable.

[0048] The frequency perturbation can be obtained from equations (6), (7), (8), (9), and (11). Active response to virtual synchronizer transitive relationships: (12) In the formula, To take into account the equivalent synchronous power coefficient after reactive power loop coupling; The transfer function from power angle disturbance to virtual internal potential amplitude disturbance; and These are the proportional and integral parameters of the reactive power control element, respectively. This equation shows that the active power response of the virtual synchronous machine is not an ideal pure inertia element; its dynamics are simultaneously affected by the virtual inertia parameters. Virtual damping parameters and equivalent synchronous power coefficient The impact of virtual inertia parameters. It can only characterize the inertial element in the virtual synchronous machine equations, and cannot be directly equated to the equivalent inertia in the sense of frequency support. .

[0049] The primary frequency modulation droop control is as follows: (13) In the formula, This is the primary frequency modulation power reference value. This is the frequency droop factor. The power grid frequency deviation is used as the reference point. This droop control directly generates active power commands from the frequency deviation, and its power contribution satisfies a linear superposition relationship.

[0050] During normal operation, the stator active power reference is determined by the wind energy capture MPPT control. The DC voltage PI controller calculates the DC-side unbalanced power and distributes this command to the DC / DC converter power command and the grid-side converter power command. (14) In the formula, and These are the reference value and the actual value of the DC bus voltage, respectively. Transfer function for DC voltage PI controller; This is the DC-side unbalanced power command output by the DC voltage PI controller; This is the DC-side power allocation coefficient, used to adjust the power distribution between the energy storage system and the grid-side converter. Its value range is... .

[0051] During normal operation, settings can be configured The unbalanced power on the DC side is entirely borne by the grid-side converter, and the energy storage side does not participate in DC voltage regulation, which corresponds to the DC voltage control mode of the grid-side converter in traditional doubly fed wind turbine units.

[0052] During frequency regulation operation, the grid-side converter power allocation described in equation (14) will no longer be updated. The grid-side converter power reference is determined by the base value before frequency regulation is put into operation and the frequency support power of the virtual synchronous machine of the grid-side converter channel. The DC bus power imbalance generated during the frequency support process is borne by the energy storage system through the bidirectional DC / DC converter to maintain the DC bus voltage stability and the frequency support power of the grid-side converter channel.

[0053] 1.3 Construction of typical frequency perturbations based on the SFR model.

[0054] The unit frequency support power response refers to the active power response formed by the unit's inertia support and primary frequency regulation support under frequency disturbances. This active power response requires a typical frequency disturbance action input. This scheme uses a typical system frequency response model under load step disturbances to describe the frequency drop process.

[0055] The system's equivalent frequency dynamics can be expressed as: (15) In the formula, For the system's equivalent inertia, For the rated frequency, This represents the change in system frequency. This is the primary frequency modulation power increment of the synchronous machine. For load disturbance, This is the load frequency adjustment coefficient.

[0056] The frequency modulation and the prime mover response can be equivalent to a first-order element: (16) In the formula, The equivalent time constant for primary frequency modulation. Let be the equivalent power-frequency coefficient of the system's primary frequency modulation. From equations (15) and (16), we can obtain: (17) In the formula, This is the system frequency response transfer function.

[0057] Equation (17) gives the typical SFR response relationship from load disturbance to system frequency deviation. This model preserves the main influences of system inertia, load frequency regulation, and primary frequency modulation response on the frequency trajectory. Based on this SFR model, the time-domain frequency deviation can be further obtained. and its rate of change This provides input for subsequent target inertia support power response analysis.

[0058] 1.4 Equivalent inertia-supported power response and parallel equivalent relationship.

[0059] equivalent inertia Characterizes the active response capability of the frequency support element to the rate of frequency change. For a given SFR model, frequency perturbations are generated. It has equivalent inertia The frequency support unit inertia support power is: (18) In the formula, This is the power reference value for the support unit. Equation (18) gives the correspondence between the equivalent inertia and the active support power. For the same frequency disturbance, the inertia support power is determined by... and The decision is made jointly. Since the closed-loop active power response of the virtual synchronous machine is not the same as the ideal inertia support power response shown in equation (18), the equivalent inertia H cannot be the same as the virtual inertia element in the virtual synchronous machine equation. The inertia support power response corresponding to equation (18) should be used as the target inertia support power response for subsequent virtual synchronous machine control parameter mapping.

[0060] For multiple parallel frequency support units responding to disturbances of the same frequency, the total inertia support power satisfies: (19) In the formula, The total inertia support power for multiple parallel units, For the first The equivalent inertia of each frequency support unit Its power reference value.

[0061] If the sum of the power reference values ​​of each support unit is used as the unified power reference value ,but: (20) Under a unified power reference value Below, the overall equivalent inertia It can be represented as: ;(twenty one) Further, we can obtain the first The equivalent inertia share of each support unit under a unified power reference value is: ;(twenty two) Equations (20)-(22) show that the overall equivalent inertia of the parallel frequency support unit is determined by the equivalent inertia of each unit and its power reference value, and can be expressed as the sum of the inertia shares of each unit under a unified power reference value. For energy storage-type doubly-fed wind turbine units using dual virtual synchronous machine control, the stator channel controlled by the rotor-side converter and the grid-side converter channel can be included as two parallel frequency support units in the calculation of the overall equivalent inertia of the unit. The inertia contributed by the two should be converted to the unit power reference value before being summed. This relationship provides a basis for subsequently decomposing the overall equivalent inertia target of the unit into the equivalent inertia targets of the stator channel and the grid-side converter channel.

[0062] 2. A method for configuring the inertia parameters of a virtual synchronous machine based on frequency-supported power response equivalence.

[0063] With equivalent inertia Using the corresponding target inertia support power response as a benchmark, the virtual synchronizer is determined. Control parameters are used to match the power response of the virtual synchronous machine to this reference, thereby achieving equivalent inertia. The virtual synchronous machine inertia supports the power response.

[0064] 2.1 Frequency Support Power Response Evaluation Indicators

[0065] For a given equivalent inertia The target inertia support power response can be determined by equation (18); For the virtual synchronous machine control strategy, its inertia support power response can be obtained by combining equation (12) with the frequency disturbance input.

[0066] Among them, the target inertia-supported power response refers to the baseline active power response calculated by the equivalent inertia H according to equation (18) under a given frequency disturbance input; the virtual synchronous machine inertia-supported power response refers to the active power response calculated by the virtual synchronous machine closed-loop model and its control parameters J and D according to equation (12) under the same frequency disturbance input. Since the power response models of the two differ, the equivalent inertia cannot be used to determine the optimal response. Directly determine the control parameters of the virtual synchronizer Therefore, it is necessary to construct an evaluation index for the power response of inertial support to quantify the time-domain power characteristics during inertial support operation, and then use the power response equivalence method to solve for the power response matching the target inertial support. , Control parameters.

[0067] The power response of inertial support is primarily manifested in the rise rate of the active support during the initial stage of the disturbance. Let the frequency disturbance occur at time [missing information]. The initial evaluation time is The initial power increase slope is defined as the first power response evaluation index.

[0068] For the target inertia-supported power response, we have: ;(twenty three) For the closed-loop power response of the virtual synchronous machine, we have: ;(twenty four) and The power increase rates of the target inertia support power response and the virtual synchronizer closed-loop power response are respectively characterized in the early stages of frequency disturbance. The closer the two are, the better the actual response of the virtual synchronizer can reproduce the support characteristics of the target equivalent inertia in the early stages of disturbance.

[0069] Besides the initial support velocity during the disturbance, the cumulative active power output during the inertia support period reflects the sustained effect of the frequency support power. Let the evaluation of the inertia support terminate at... The power integral during the inertia support period is defined as the second power response evaluation index.

[0070] For the target inertia-supported power response, we have: (25) For the closed-loop power response of the virtual synchronous machine, we have: (26) In the formula, and The cumulative energy of the target inertia support power response and the virtual synchronous machine closed-loop power response during the inertia support period is represented, respectively. Compared with the single-point power amplitude, the power integral can reflect the continuous output capability and overall response effect during the inertia support process.

[0071] 2.2 Parameter configuration and error verification of virtual synchronous machine based on power response consistency.

[0072] Equivalent inertia target The corresponding virtual synchronizer parameter configuration should ensure that the target inertia support power response and the virtual synchronizer inertia support power response maintain consistency in key dynamic characteristics, except for the initial power increase slope. Power integral during inertia support In addition, to further constrain the consistency of the overall power response during the inertia support phase, a normalized power error index is introduced.

[0073] based on The index, defined as the relative error of the initial power increase slope, is: (27) based on The index is defined as follows: the relative error of power integral during inertia support is: (28) The normalized power error during the inertia support stage is defined as: (29) Therefore, the comprehensive error function is defined as follows: (30) In the formula, , and These are the weighting coefficients for the relative error of the power increase slope, the relative error of the power integral, and the normalized power error, respectively, satisfying... , , ,and The three parameters can be set according to the importance attached to the initial power rise rate of the disturbance, the cumulative power contribution during the inertia support period, and the overall power waveform consistency.

[0074] Within the control parameter boundaries of the virtual synchronous machine, power response equivalence is used. J , D The parameter solution can be transformed into a boundary constraint optimization problem of minimizing the comprehensive error function: (31) In the formula, , , and For the control parameter boundaries of the virtual synchronizer; The damping ratio of the dominant oscillation mode in the active response of the virtual synchronous machine. Its lower limit; For a given equivalent inertia target The minimum comprehensive error. The parameter combination that minimizes equation (31) is denoted as... , The two respectively represent a given equivalent inertia target. The optimal virtual inertia parameters and optimal virtual damping parameters are obtained through the power response equivalence method, and satisfy the following: (32) Equation (32) gives the equivalent inertia target. The power response consistency error corresponding to the optimal parameters. Solving equation (31) will yield the result. and , The relationship between the virtual synchronizer parameter configurations.

[0075] Select typical equivalent inertia targets of low, medium, and high, and determine their corresponding values. , Target inertia support power response under three typical inertia targets. Power response supported by virtual synchronous machine inertia like Figure 2 As shown, Figure 2 Among them, (a)H=1.2s; (b)H=3s; (c)H=5s.

[0076] Depend on Figure 2It can be seen that, under different equivalent inertia targets, the power response of the virtual synchronous machine inertia support can maintain a high degree of consistency with the target inertia support power response. Since the initial power increase rate of the virtual synchronous machine inertia support power response is slightly lower than that of the target inertia support power response, its peak value is correspondingly higher than the peak value of the target response power, thus ensuring the consistency of the cumulative power contribution during the inertia support stage.

[0077] Given Lower comprehensive error function exist contour lines in the plane, such as Figure 3 As shown in (a). By Figure 3 (a) It can be seen that the comprehensive error function is in The existence of a clearly defined low-error region within the plane indicates that the boundary constraint optimization solution results are identifiable.

[0078] different Minimum comprehensive error like Figure 3 As shown in (b). In Within the range, the initial power increase rate error Relative error of power integral during inertia support period and normalized power error All remain at low levels, indicating that the desired virtual synchronizer parameters can achieve good power response equivalence under different equivalent inertia targets. Among them, with... Increase The slight increase indicates that the overall waveform matching difficulty of the power response increases under the high equivalent inertia target.

[0079] The virtual synchronizer parameter configuration results under different equivalent inertia targets are as follows: Figure 4 As shown. By Figure 4 As can be seen from (a) in the figure, with the equivalent inertia target Increase the optimal inertia parameter The approximately linear increase indicates This primarily determines the inertia-supported response strength of the virtual synchronizer. Figure 4 As can be seen from (b) in the figure, the damping parameter Follow The increase shows a trend of rising and then slowing down, indicating that It is mainly used to adjust the power response damping and the shape near the peak value, and its marginal effect is weakened under higher inertia targets.

[0080] 2.3 Target inertia conversion and parameter configuration for dual virtual synchronous machines of rotor-side converter / grid-side converter.

[0081] For energy storage-type doubly-fed induction generator (DFIG) wind turbines under a dual virtual synchronous machine strategy, the overall equivalent inertia target of the unit needs to be converted into inertia indices under the respective power reference values ​​of the stator channel and the grid-side converter channel, and the power response equivalent method should be called to solve for each inertia. , Control parameters.

[0082] To ensure the target equivalent inertia of the same unit under different operating conditions To ensure consistent power response, a fixed power reference is adopted for the entire unit, the stator channel, and the grid-side converter channel. Let the overall unit power reference value be... The power reference values ​​for the stator channel and the grid-side converter channel are respectively and ,but: (33) The equivalent inertia of the sub-channel and the grid-side converter channel under the unit power reference value are set as follows: and According to equations (21)-(22), the overall equivalent inertia target of the unit is... Decomposed into: (34) In the formula, and These represent the equivalent inertia of the stator channel and the grid-side converter channel when converted to the unit power reference value, respectively. Their specific values ​​are determined by the rotor kinetic energy reserve, the availability of DC energy storage, and the power margin of the grid-side converter.

[0083] Further, from equation (22), the target equivalent inertia of the stator channel and the grid-side converter channel under their respective power reference values ​​can be obtained as follows: (35) Furthermore, the virtual synchronous machine of the stator channel and the virtual synchronous machine of the grid-side converter channel respectively use the corresponding equivalent inertia target as input, and solve their respective virtual synchronous machine control parameters according to equations (30)-(31): (36) Equations (33)-(36) give the target of the overall equivalent inertia of the unit. To dual virtual synchronous machine control parameters The calculation relationship is as follows: The overall equivalent inertia target of the unit is first decomposed into inertia components of the stator channel and grid-side converter channel according to the unit power reference value, and then converted into equivalent inertia targets under the power reference values ​​of the two channels. Finally, the control parameters of the virtual synchronous machine of the two channels are obtained through the power response equivalence method. This method maintains the stability and controllability of the overall inertia support power response of the unit by allocating the inertia support tasks of the stator channel and grid-side converter channel under different speeds and energy storage conditions.

[0084] 3. Energy storage type doubly fed wind turbine generator set dual virtual synchronous machine cooperative frequency support control strategy.

[0085] The dual virtual synchronous machine coordinated control needs to determine the inertia support capacity of the stator channel and the grid-side converter channel, as well as the allocation ratio of the primary frequency regulation droop coefficient, based on the rotor kinetic energy reserve, DC energy storage status, and grid-side converter power up-adjustment margin, so that the overall frequency support power response of the unit can track the set target within the range achievable under the current operating conditions.

[0086] 3.1 Characterization of dual-channel frequency support capability and boundary constraints.

[0087] The frequency-supported power of the stator channel comes from the release of rotor kinetic energy and is constrained by the rotational speed; the frequency-supported power of the grid-side converter channel comes from the release of DC energy storage and is simultaneously constrained by the energy storage state of charge and the power up-adjustment margin of the grid-side converter.

[0088] Based on the relationship between rotor kinetic energy and the square of rotational speed, the rotor kinetic energy reserve coefficient is defined. for: (37) In the formula, The rotor's mechanical angular velocity before frequency disturbance. Minimum permissible speed, Rated speed; Characterizing the level of rotor kinetic energy that can be released at the current speed, its calculation results are limited to... Within the range.

[0089] Define the available state coefficient of DC energy storage for: (38) In the formula, This is the pre-charged state before frequency perturbation. The minimum permissible state of charge, For reference state of charge; Characterizing the energy reserve level of DC energy storage that can be used for frequency support, the calculation results are limited to... Within the range.

[0090] Define the power upsizing margin factor for grid-side converters. for: (39) In the formula, This is the upper limit of the grid-side converter power. The active power of the grid-side converter is affected by frequency disturbance. The power up-adjustment margin of the grid-side converter is characterized at the pre-disturbance operating point, and its calculation results are limited to... Within the range.

[0091] The state of charge of energy storage and the up-adjustment margin of grid-side converter power jointly determine the available frequency support capability of grid-side converter channels. The available frequency support coefficient of grid-side converter channels is defined as: (40) In the formula, This also reflects both the energy storage constraint and the grid-side converter's power upscaling margin constraint. When the energy storage's state of charge is low or the grid-side converter's power upscaling margin is insufficient... Reduced; when both the energy storage state of charge and the grid-side converter power up-adjustment margin are sufficient. Close to 1.

[0092] Under current operating conditions, the maximum borne equivalent inertia components of the stator channel and the grid-side converter channel at the unit power reference value are respectively denoted as: and .in, Determined by the rotor's kinetic energy reserve and the lower limit of its speed. It is jointly determined by the energy storage state of charge and the power up-adjustment margin of the grid-side converter. The two constitute the boundary constraints for the inertia distribution of the dual virtual synchronous machines.

[0093] 3.2 Coordinated allocation of inertia and droop coefficient of dual virtual synchronous machines.

[0094] The dual virtual synchronous machine frequency support output allocation is used to coordinate the inertia support and primary frequency regulation power output of the stator channel and the grid-side converter channel, so that the overall frequency support response of the unit meets the given target. In terms of allocation logic, when the grid-side converter channel has sufficient available capacity, DC energy storage support is prioritized to reduce rotor kinetic energy release and its impact on wind energy capture; when the grid-side converter channel is limited, the stator channel provides supplementary support to maintain the overall frequency support capability of the unit.

[0095] Based on the stator channel rotor kinetic energy reserve coefficient and the grid-side converter channel availability coefficient, the grid-side converter channel inertia support coefficient is defined. for: (41) In the formula, This characterizes the proportion of the overall equivalent inertia target of the unit that is borne by the grid-side converter channels. A higher availability factor for the grid-side converter channels results in a higher overall inertia. The larger the value, the lower the availability factor of the grid-side converter channel, and the more the inertia support task shifts to the stator channel. When and When both are zero, there is no inertia support margin on either side under the current operating conditions.

[0096] For a given unit equivalent inertia target The equivalent inertia component of the grid-side converter channel is: (42) The equivalent inertia component of the stator channel is determined by the overall unit target and the actual load borne by the grid-side converter channel, and is constrained by the stator channel inertia boundary: (43) Equations (42) and (43) give the inertia allocation relationship where the grid-side converter takes priority and the stator channel supplements. When the stator channel limiting in equation (43) does not occur, the unit can achieve the target equivalent inertia under the current operating conditions. When stator channel limiting occurs, the current rotor kinetic energy reserve and the available capacity of the grid-side converter are insufficient to fully support the target inertia. The unit's current maximum achievable equivalent inertia is... for: (44) According to equation (35), and The target inertia can be converted into the equivalent inertia target under the power reference values ​​of each side. and Furthermore, based on equations (30) and (31), the corresponding control parameters of the stator channel virtual synchronizer and the grid-side converter channel virtual synchronizer are calculated.

[0097] The primary frequency regulation power command is linearly determined by the frequency deviation and the droop coefficient; therefore, dynamic response equivalence is not required for primary frequency regulation. This scheme allocates the primary frequency regulation droop coefficient of the unit according to the inertia support ratio of the two channels. The allocation ratios of the primary frequency regulation droop coefficients for the stator channel and the grid-side converter channel are defined as follows: (45) Let the total droop coefficient of the unit be... The droop coefficients for the stator channel and the grid-side converter channel are respectively: (46) Equations (42-43, 46) present a method for allocating frequency support output for dual virtual synchronous machines, taking into account inertia and primary frequency regulation. For inertia support, the grid-side converter channel's inertia support load is first determined by the grid-side converter channel inertia support load coefficient, then the stator channel's load is determined by the overall unit target, and the feasibility of the frequency support target under the current operating conditions is judged through boundary constraints. The droop coefficient for primary frequency regulation is allocated according to the ratio of the inertia support load of the two channels.

[0098] Let the target equivalent inertia of the unit be... The inertia distribution between the stator channel and the grid-side converter channel under different speed and energy storage state of charge conditions is as follows: Figure 5 As shown. The rotational speed characterizes both the rotor kinetic energy reserve of the stator channel and influences the active power of the grid-side converter before disturbance. It affects the up-adjustment margin of grid-side converter power; the state of charge of energy storage characterizes the available energy level of DC energy storage.

[0099] Depend on Figure 5 (a) It can be seen that when the energy storage has a high state of charge and a low speed, the grid-side converter channel availability is strong. The relatively large value reflects the allocation logic that prioritizes the use of DC energy storage. Figure 5 (b) It can be seen that as the load on the inertia support of the grid-side converter channels decreases, the load on the inertia support of the stator channels also decreases. The corresponding increase indicates that the frequency support task has shifted from the grid-side converter channel to the stator channel, in order to maintain the overall inertia support capability of the unit. Figure 5 (c) It can be seen that in the medium-to-high speed or high energy storage state of charge region, the unit can achieve inertia. It can achieve the given unit inertia target; however, in the low-speed and low-energy-storage-charged state region... If the value is lower than the target value, it indicates that the unit's frequency support capability is limited under the current operating conditions.

[0100] Since the droop coefficient of a single frequency modulation is directly determined according to the ratio of the inertia support load of the two channels, its changing trend is similar to... and The allocation results are consistent.

[0101] The parameter configuration of the virtual synchronous machine based on frequency-supported power response equivalence and the frequency support load allocation between the stator channel and the grid-side converter channel together constitute the core of the collaborative control of the dual virtual synchronous machines in the energy storage-type doubly-fed induction generator (DFIG) wind turbine. Its overall control structure is as follows: Figure 6 As shown.

[0102] 4. Experimental verification.

[0103] This scheme verifies the proposed method based on the HIL real-time simulation platform. A model of a doubly-fed induction generator (DFIG) wind turbine, a back-to-back converter, a DC energy storage unit, and grid frequency disturbances was established in the HIL platform. Relevant model parameters and control parameters were set according to Table 1, and experimental data were obtained from real-time simulation. First, wind speed fluctuations and energy storage charging operation conditions were designed to verify the power control stability of the unit's dual virtual synchronous machine channels under power coupling conditions. Then, four typical operating conditions—high / low speed and high / low energy storage state of charge—were set up to verify the effectiveness of the proposed method from three levels: equivalent power response supported by inertia, power response supported by the coordinated frequency of the dual virtual synchronous machines, and system frequency response.

[0104] Table 1 HIL Real-time Simulation Model and Control Parameters

[0105] 4.1 Verification of power coupling control of energy storage doubly fed wind turbine under wind speed fluctuations.

[0106] The test conditions used a variable wind speed sequence as input, and the time axis was compressed to construct a variable wind speed scenario with actual fluctuation characteristics. The initial state of charge of the energy storage was set to 0.6, and... Energy storage state of charge control is always enabled, with a target value set to 0.8. Test results are as follows: Figure 7 As shown.

[0107] Depend on Figure 7 (a)- Figure 7 (e) It can be seen that the wind speed exhibits continuous fluctuation characteristics during the test. The rotor angular velocity, stator and rotor current amplitudes, and stator power all change accordingly with the wind speed, and the rotor current frequency adjusts with the rotational speed. Throughout the process, the mechanical operating state is consistent with the changes in electrical variables, and no significant impact or oscillation amplification occurs in the stator current and rotor current.

[0108] Depend on Figure 7 (f)- Figure 7 (h) indicates that after the state-of-charge control is initiated at time t1, the energy storage enters the charging process, and the energy storage power... P es Increase; as the state of charge gradually approaches the target value, the energy storage charging power gradually decreases. Grid-side converter power P gsc The power flowing into the DC bus from the rotor side is balanced with the charging power from the energy storage side in order to control the DC voltage. P gsc With stator power P s Together they constitute the unit's output power P wt The changes reflect the impact of wind speed fluctuations and the energy storage charging process on the unit's power.

[0109] Depend on Figure 7 (i) and Figure 7 (j) shows that the state of charge gradually increases from 0.6 to close to 0.8 under control, and the DC side voltage... u dc Throughout the process, the voltage remained near the rated value. Based on the above results, it can be concluded that the energy storage-type doubly-fed induction generator (DFIG) can achieve stable control of stator channel power, regulation of energy storage state of charge, and stable control of DC voltage under this operating condition.

[0110] 4.2 Equivalent verification of power response supported by inertia.

[0111] Table 2 shows four typical operating conditions with combinations of high / low wind speed and high / low energy storage state of charge.

[0112] Table 2 Typical Operating Conditions of Energy Storage Doubly Fed Wind Turbine Units

[0113] In this scenario, only inertial support control is enabled, and the system frequency response is generated by the SFR model shown in equation (17), with a load disturbance amplitude of 0.1 pu (per unit). The test results are as follows: Figure 8 As shown.

[0114] Depend on Figure 8 (a) It can be seen that after the load disturbance, the grid frequency drops from 50Hz to about 49.75Hz, providing the same frequency disturbance input for the equivalent verification of the inertia-supported power response under the four operating conditions.

[0115] Depend on Figure 8 (b) and Figure 8 (c) It can be seen that under different wind speeds and energy storage state of charge conditions, the stator channel and the grid-side converter channel output power response according to their respective allocated inertia support targets. Since the available rotor kinetic energy of the stator channel and the available energy storage state of the grid-side converter channel are different, the stator power and grid-side converter power exhibit different response characteristics under different operating conditions, reflecting the allocation results of the proposed method for the dual-channel inertia support task under operating state constraints.

[0116] Figure 8 (d) presents the power response of the wind turbine. At the same wind speed, the power curves of the turbines under different energy storage states of charge are basically consistent. Further extraction of the change in turbine power relative to the steady-state value before frequency disturbance yields the following results: Figure 8 As shown in (e), it can be seen that although the power sharing between the stator channel and the grid-side converter channel is different under different operating conditions, the incremental power of the unit can track the target inertia to support the power response under all four operating conditions, and maintain good consistency with the target curve. This result is consistent with the power response consistency optimization analysis in Section 2.2.

[0117] The above results show that the proposed power response equivalent configuration method can coordinate the control parameters of the stator channel virtual synchronous machine and the grid-side converter channel virtual synchronous machine under different wind speeds and energy storage state of charge conditions, so that the overall inertia support power response of the unit matches the given target inertia support power response.

[0118] 4.3 Verification of power response supported by dual virtual synchronous machines with coordinated frequency.

[0119] Under the four typical operating conditions shown in Table 2, inertia support control and primary frequency modulation control are simultaneously enabled, with the frequency disturbance settings consistent with Section 4.2. The test results are as follows: Figure 9 As shown.

[0120] Depend on Figure 9 (a)- Figure 9 (c) It can be seen that, under the same frequency drop input, the stator channel and the grid-side converter channel allocate frequency support power according to the operating state. Under high wind speed conditions, the stator channel has sufficient rotor kinetic energy reserves and the grid-side converter has a low power up-adjustment margin, so the frequency support power is mostly borne by the stator channel; when the energy storage state of charge and the grid-side converter power up-adjustment margin are high, the proportion borne by the grid-side converter channel increases.

[0121] Depend on Figure 9 (d) and Figure 9 (e) It can be seen that the incremental power of the unit remains relatively consistent within approximately 7 seconds after the start of frequency support under the four operating conditions. Due to differences in rotor kinetic energy reserves and energy storage state of charge, the process of power withdrawal under different operating conditions varies to some extent.

[0122] Depend on Figure 9 (f) and Figure 9 (g) It is evident that the release of rotor kinetic energy during frequency support causes a decrease in speed, followed by a gradual increase in speed due to speed recovery control. Speed ​​recovery requires active power load reduction in the stator channel. When the low state of charge (SBC) of the energy storage leads to limited support capacity of the grid-side converter channel, the speed recovery process can result in a negative increase in unit power. SBC control keeps the SBC within constraints during frequency support, preventing it from falling below the 0.2 lower limit. In summary, the proposed dual virtual synchronous machine cooperative control method can coordinate the frequency support power output of the stator channel and the grid-side converter channel under different wind speeds and SBC conditions, ensuring good consistency in the unit-level frequency support power response during the initial stage of disturbance.

[0123] 4.4 System frequency response comparison and verification.

[0124] Under the same operating conditions as described in Section 4.3, and assuming a wind power penetration rate of 30%, the frequency support power output of the energy storage-type doubly-fed induction generator (DFIG) is incorporated into the SFR model to obtain the system frequency response. The results are as follows: Figure 10As shown.

[0125] Depend on Figure 10 It can be seen that, compared to the case where the wind turbine does not participate in frequency support, the participation of the energy storage-type doubly-fed induction generator (DFIG) in frequency support under all four operating conditions can reduce the frequency drop amplitude in the initial stage of disturbance and mitigate the frequency decline process. These results demonstrate that the proposed dual-virtual synchronous machine cooperative frequency support method can improve the system frequency dynamics in the initial stage of disturbance under different wind speeds and energy storage state of charge conditions.

[0126] This scheme employs an equivalent method for frequency-supported power response to establish a correspondence between the target inertia-supported power response and the control parameters of the stator channel virtual synchronous machine and the grid-side converter channel virtual synchronous machine, enabling the unit's inertia-supported power response to match the given target inertia-supported power response. Based on this, and considering rotor kinetic energy reserve, energy storage state of charge, and grid-side converter power upsizing margin, the scheme coordinates the allocation ratio of inertia support load for the stator channel and grid-side converter channel, as well as the primary frequency regulation droop coefficient. Hardware-in-the-loop verification results demonstrate that under four typical operating conditions—high / low speed and high / low energy storage state of charge—the proposed method can adjust the frequency support load for the stator channel and grid-side converter channel according to the operating state. Under each operating condition, the overall inertia-supported power response of the unit can track the target inertia-supported power response, and the overall frequency-supported power response remains consistent. The verification results indicate that the proposed method can maintain the stability and controllability of the unit-level frequency support response when operating conditions change, improving the frequency support effect of energy storage-type doubly-fed induction generator (DFIG) wind turbines under a wide range of operating conditions.

[0127] Correspondingly, the power-equivalent energy storage type doubly-fed wind turbine dual virtual synchronous machine control system includes: The target setting module is configured to determine the unit equivalent inertia target and the unit primary frequency regulation droop coefficient of the energy storage type doubly fed wind turbine according to the scheduling instructions or preset conditions. The allocation module is configured to: determine the inertia support load of the stator channel and the grid-side converter channel and the allocation ratio of the primary frequency regulation droop coefficient according to the current operating status parameters of the wind turbine, and decompose the equivalent inertia target of the unit into the equivalent inertia target of the stator channel and the equivalent inertia target of the grid-side converter channel according to the inertia support load; The parameter configuration and control execution module is configured to: use the power response equivalence method to determine the stator channel virtual synchronous machine control parameters and the grid-side converter channel virtual synchronous machine control parameters according to the stator channel equivalent inertia target and the grid-side converter channel equivalent inertia target, respectively; the stator channel virtual synchronous machine control parameters are used to control the rotor-side converter, and the grid-side converter channel virtual synchronous machine control parameters are used to control the grid-side converter; The power response equivalence method is as follows: the control parameters of the virtual synchronous machine are obtained by minimizing the comprehensive error between the closed-loop power response of the virtual synchronous machine and the power response of the target inertia support.

[0128] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A power-equivalent energy storage type doubly-fed wind turbine dual-virtual synchronous machine control method, characterized in that, Includes the following steps: Based on dispatch instructions or preset conditions, determine the unit equivalent inertia target and the unit primary frequency regulation droop coefficient of the energy storage type doubly fed wind turbine. Based on the current operating parameters of the wind turbine, determine the inertia support borne by the stator channel and the grid-side converter channel, as well as the allocation ratio of the primary frequency regulation droop coefficient. Based on the inertia support borne by the stator channel, decompose the equivalent inertia target of the turbine into the equivalent inertia target of the stator channel and the equivalent inertia target of the grid-side converter channel. Using the power response equivalent method, the control parameters of the stator channel virtual synchronous machine and the control parameters of the grid-side converter channel virtual synchronous machine are determined according to the equivalent inertia target of the stator channel and the equivalent inertia target of the grid-side converter channel, respectively. The control parameters of the stator channel virtual synchronous machine are used to control the rotor-side converter, and the control parameters of the grid-side converter channel virtual synchronous machine are used to control the grid-side converter. The operating status parameters include rotor speed, energy storage state of charge, current active power of grid-side converter, and upper limit of grid-side converter power. Among them, the power response equivalent method is: taking the minimization of the comprehensive error between the closed-loop power response of the virtual synchronous machine and the target inertia support power response as the objective, the control parameters of the virtual synchronous machine are obtained; The comprehensive error is specifically as follows: ； in, , and The relative error of the slope for increasing power respectively Relative error of power integral and normalized power error The weighting coefficients, These are the equivalent inertia, virtual inertia parameter, and virtual damping parameter, respectively.

2. The power-equivalent energy storage type doubly-fed wind turbine dual virtual synchronous machine control method as described in claim 1, characterized in that, The relative error of the initial power increase slope is as follows: ； The relative error of power integral during inertia support is as follows: ； Normalized power error, specifically: ； in, and The power increase rates of the target inertia-supported power response and the virtual synchronous machine closed-loop power response are respectively characterized in the early stage of frequency disturbance; and The cumulative energy of the target inertia support power response and the virtual synchronous machine closed-loop power response during the inertia support period is represented, respectively. Power response to target inertia Power response to support the inertia of the virtual synchronous machine; The time when the frequency disturbance occurs. This is the time when the inertia support evaluation ends.

3. The power-equivalent energy storage type doubly-fed wind turbine dual virtual synchronous machine control method as described in claim 2, characterized in that, The rate of increase in power of the target inertia-supported power response and the virtual synchronous machine closed-loop power response during the initial stage of frequency disturbance. and Specifically: ； ； The cumulative energy of the target inertia-supported power response and the virtual synchronous machine closed-loop power response during the inertia support period. and Specifically: ； ； in, Power response to target inertia Power response to support the inertia of the virtual synchronous machine. This is the initial evaluation point.

4. The power-equivalent energy storage type doubly-fed wind turbine dual virtual synchronous machine control method as described in claim 1, characterized in that, The power response equivalent method also includes setting boundary constraints on the control parameters of the virtual synchronous machine, and solving for the control parameters that minimize the comprehensive error under the boundary constraints, as shown in the following equation: ； in, , , and For the control parameter boundaries of the virtual synchronizer; The damping ratio of the dominant oscillation mode in the active response of the virtual synchronous machine. Its lower limit; For a given equivalent inertia target The minimum overall error.

5. The power-equivalent energy storage type doubly-fed wind turbine dual virtual synchronous machine control method as described in claim 1, characterized in that, The allocation ratio of inertia support and primary frequency regulation droop coefficient between the stator channel and the grid-side converter channel is determined based on the current operating parameters of the wind turbine, including: Determine the rotor kinetic energy reserve coefficient based on the rotor speed: ; Determine the available state factor of DC energy storage based on the energy storage state of charge: ; The power adjustment margin factor for the grid-side converter is determined based on the current active power of the grid-side converter and the upper limit of the grid-side converter's power: ; The frequency support availability factor of the grid-side converter is determined based on the DC energy storage availability state factor and the grid-side converter power upshortage margin factor: ; in, The rotor's mechanical angular velocity before frequency disturbance. Minimum permissible speed, Rated speed, This is the pre-charged state before frequency perturbation. The minimum permissible state of charge, For reference state of charge; This is the upper limit of the grid-side converter power. The active power of the grid-side converter before frequency disturbance.

6. The power-equivalent energy storage type doubly-fed wind turbine dual virtual synchronous machine control method as described in claim 1, characterized in that, The allocation ratio of inertia support and primary frequency regulation droop coefficient between the stator channel and the grid-side converter channel is determined based on the current operating parameters of the wind turbine generator, and also includes: The inertia support factor of the grid-side converter channel is determined based on the frequency support availability factor of the grid-side converter. Further determine the equivalent inertia components of the grid-side converter channel. Equivalent inertia components of stator channel Specifically: ； ； ； in, The target is the equivalent inertia of the generator unit. and These represent the maximum equivalent inertia components that the stator channel and the grid-side converter channel can bear under the unit power reference value, respectively.

7. The power-equivalent energy storage type doubly-fed wind turbine dual virtual synchronous machine control method as described in claim 6, characterized in that, Grid-side converter channel inertia support coefficient It is also used to determine the primary frequency regulation droop coefficient allocation ratio between the stator channel and the grid-side converter channel, so that the droop coefficients of the stator channel and the grid-side converter channel are allocated according to the inertia support bearing ratio, as shown in the following formula: ； ； in, and These are the droop coefficient allocation ratios for the stator channel and the grid-side converter channel, respectively. This is the overall droop coefficient of the unit. and These are the droop coefficients for the stator channel and the grid-side converter channel, respectively.

8. A power-equivalent energy storage type doubly-fed wind turbine dual virtual synchronous machine control system, used to implement the control method as described in any one of claims 1-7, characterized in that, include: The target setting module is configured to determine the unit equivalent inertia target and the unit primary frequency regulation droop coefficient of the energy storage type doubly fed wind turbine according to the scheduling instructions or preset conditions. The allocation module is configured to: determine the inertia support load of the stator channel and the grid-side converter channel and the allocation ratio of the primary frequency regulation droop coefficient according to the current operating status parameters of the wind turbine, and decompose the equivalent inertia target of the unit into the equivalent inertia target of the stator channel and the equivalent inertia target of the grid-side converter channel according to the inertia support load; The parameter configuration and control execution module is configured to: use the power response equivalence method to determine the stator channel virtual synchronous machine control parameters and the grid-side converter channel virtual synchronous machine control parameters according to the stator channel equivalent inertia target and the grid-side converter channel equivalent inertia target, respectively; the stator channel virtual synchronous machine control parameters are used to control the rotor-side converter, and the grid-side converter channel virtual synchronous machine control parameters are used to control the grid-side converter.

Images