Inertia response stabilization control method and system for self-synchronous voltage source doubly-fed wind turbine generator sets

Abstract

The present invention provides a method and system for stabilizing the inertia response of a self-synchronous voltage source doubly fed wind turbine generator set, comprising: step S1: establishing a linearized state space model of a doubly fed wind turbine generator set grid-connected system; step S2: analyzing a stabilizing control coefficient K based on the linearized state space model of the doubly fed wind turbine generator set grid-connected system; PSS , inertia control time constant T c and inertia control gain K c Stable regions under different grid short-circuit ratios; Step S3: Stabilizing control coefficient K based on the stable regions under different grid short-circuit ratios PSS , inertia control time constant T c and inertia control gain K c The inertia response stability control and corresponding dynamic response characteristics of the self-synchronous voltage source doubly fed wind turbine are realized; the linearized state space model of the doubly fed wind turbine grid-connected system is obtained by adopting the small signal linearization modeling method at different working points to obtain the small signal mathematical model of the doubly fed wind turbine grid-connected system.

Description

Technical Field

[0001] The present invention relates to the field of wind turbine control technology, and in particular to a method and system for stabilizing inertia response control of a self-synchronous voltage source doubly fed wind turbine, and more particularly to a method for designing inertia response control parameters of a self-synchronous voltage source doubly fed wind turbine. Background Art

[0002] Traditional doubly-fed wind turbine converters mostly use vector control and lack inertia support capabilities. With the increasing penetration of wind turbines, new power systems are characterized by reduced equivalent inertia and weakened grid strength. The recently released "Wind Turbine Grid Adaptability Test Procedure GB / T 36994-2018" explicitly requires wind turbines to have sufficient inertia support capabilities and specifies the active power regulation and frequency deadband required for wind turbine inertia response. The self-synchronous voltage source control method of "rotor-side inertia transfer + grid-side inertia synchronization" can enable doubly-fed wind turbines to have inertia response capabilities. This method only requires changes to the control structure of the grid-side converter of traditional units, with minimal modifications to the rotor-side converter, making it easier to upgrade and retrofit conventional units and offering significant practical value. Under this control method, the DC-side voltage of a doubly-fed wind turbine can autonomously sense grid frequency changes. The inertia transfer controller detects the rate of change of the DC voltage and introduces active power control into the rotor-side converter. This absorbs or releases rotor kinetic energy to counteract grid frequency fluctuations, thereby providing inertia support to the grid.

[0003] After being connected to the power grid, self-synchronous voltage source doubly fed wind turbines can effectively improve the equivalent inertia of the power system. However, due to the time-varying characteristics of the grid system's equivalent inertia, the inertia response of the wind turbine after a disturbance is complex and variable, which can easily cause wind turbine oscillation and instability. The inertia response characteristics and weak grid operation stability of doubly fed wind turbines are greatly affected by their control parameters. Therefore, to improve the inertial response stability capability of self-synchronous voltage source doubly fed wind turbines, it is necessary to accurately evaluate the equivalent inertia of the doubly fed wind turbines, deeply analyze their inertia response characteristics, and propose a practical method for designing the inertia response control parameters of self-synchronous voltage source doubly fed wind turbines.

[0004] Patent document CN115102198A (application number: 202210609071.6) discloses a VSG energy storage control parameter design method and system for inertia support. The present invention includes obtaining the operating data of the power system under frequency disturbance events when the system inertia changes, and calculating the inertia time constant of the synchronous generator and the inertia time constant of the static load respectively; and further calculating the inertia time constant required to be provided by the corresponding energy storage system according to the change in the inertia time constant of the synchronous generator and the static load respectively; finally, the damping coefficient of the energy storage system is determined based on the total inertia time constant required to be provided by the energy storage system to ensure system stability. This patent proposes a VSG energy storage control parameter design method for inertia support, which is only for energy storage systems and has not been tested on doubly fed wind turbines. In addition, this patent does not consider the impact of grid impedance changes on system stability when designing parameters. However, the present invention implements a control parameter design method for inertia response of self-synchronous voltage source doubly fed wind turbines, and considers the impact of grid impedance changes on parameters, so that the unit can operate stably under a wide range of grid impedance changes and has good inertia response characteristics.

[0005] Patent document CN111725838B (application number: 202010597325.8) discloses a stability control system for a full-power wind turbine and its parameter design method. The system includes a full-power wind turbine with voltage source control, wherein a generator-side stability controller is provided within the inertia transfer control loop of the wind turbine. The generator-side stability controller is configured to adjust the phase of the active power output by the generator-side converter in the wind turbine, thereby improving the stability of the stability control system. The grid-side converter of the wind turbine is connected to the grid-side stability controller, which is configured to increase the grid-side damping power coefficient, thereby improving the stability of the stability control system. This patent proposes a stability control system for a full-power wind turbine and its parameter design method, which can reduce oscillation and instability caused by increased inertia transfer control in voltage source full-power wind turbines, thereby improving the stability of the wind turbine. This patent only addresses full-power wind turbines and does not address doubly-fed wind turbines. Furthermore, the patent does not optimize the inertia response characteristics of the wind turbine or consider the impact of grid impedance variations. The present invention implements a control parameter design method for the inertia response of a self-synchronous voltage source doubly fed wind turbine, sets the dead zone, rise time and inertia time constant of the inertia response, and takes into account the influence of grid impedance changes on the parameters, thereby enabling the unit to have better inertia response characteristics. Summary of the Invention

[0006] In view of the defects in the prior art, the object of the present invention is to provide a method and system for stabilizing the inertia response of a self-synchronous voltage source doubly-fed wind turbine generator set.

[0007] According to the present invention, a method for stabilizing inertia response of a self-synchronous voltage source doubly-fed wind turbine generator system is provided, comprising:

[0008] Step S1: Establishing a linearized state space model of the doubly-fed wind turbine grid-connected system;

[0009] Step S2: Analyze the stabilizing control coefficient K based on the linearized state space model of the doubly fed wind turbine grid-connected system PSS , inertia control time constant T c and inertia control gain K c Stable regions under different grid short-circuit ratios;

[0010] Step S3: Stabilization control coefficient K based on the stable region under different grid short-circuit ratios PSS , inertia control time constant T c and inertia control gain K c Realize the inertia response stability control and corresponding dynamic response characteristics of self-synchronous voltage source doubly fed wind turbines;

[0011] The linearized state space model of the doubly-fed wind turbine grid-connected system is a small signal mathematical model of the doubly-fed wind turbine grid-connected system obtained by adopting a small signal linearization modeling method at different working points.

[0012] Preferably, the step S1 adopts: establishing a mathematical model of the self-synchronous voltage source doubly-fed wind turbine generator system connected to a weak grid and performing linearization to obtain a linearized state space model of the doubly-fed wind turbine generator system connected to the grid.

[0013] Preferably, the linearized state space model of the doubly-fed wind turbine grid-connected system includes: a linearized small signal mathematical model of the rotor-side converter current inner loop control loop and a linearized small signal mathematical model of the grid-side converter output current;

[0014] The linearized small signal mathematical model of the rotor-side converter current inner loop control loop adopts:

[0015]

[0016]

[0017]

[0018] Where ω1 is the synchronous electrical angular velocity; σ is the leakage reactance coefficient; k p2 and k p4 is the current inner loop proportional coefficient; X r is the rotor mutual inductance in the dq coordinate system; R r is the rotor resistance; i rd 、i rq are the dq axis components of the rotor current respectively; Δi rd , Δi rqare the small disturbance quantities of the dq axis components of the rotor current respectively; are the rotor current dq axis component command values ​​respectively; are the small disturbances of the dq-axis components of the rotor current reference value, respectively; x2 and x4 are the outputs of the integrators in the d-axis and q-axis current control loops; Δx2 and Δx4 are the small disturbances of the outputs of the integrators in the d-axis and q-axis current control loops, respectively; Δx1 and Δx3 represent the small disturbances of the outputs of the integrators in the active and reactive power control loops, respectively; Δx5 represents the small disturbance of the output of the integrator in the virtual inertia control link, and k i1 Indicates the active outer loop integral coefficient, k i2 Indicates the rotor d-axis current inner loop integral coefficient, k i3 Indicates the reactive outer loop integral coefficient, k i4 represents the rotor q-axis current inner loop integral coefficient, Indicates the small disturbance of the stator active reference value, ΔP s represents the small disturbance of stator active power, represents a small disturbance of additional power, Indicates the small disturbance of the stator reactive power reference value, ΔQ s Represents the small disturbance of stator reactive power, T c Indicates the time constant of inertia transfer control, Δu dc represents the small disturbance of DC bus voltage, Δs represents the small disturbance of slip rate, H represents the generator inertia time constant, P s (0) Indicates the steady-state value of stator active power, s (0) Indicates the steady-state value of the slip rate, X m and X s are the mutual inductance of stator and rotor and the self-inductance of stator in dq coordinate system respectively;

[0019] The linearized small signal mathematical model of the grid-side converter output current adopts:

[0020]

[0021]

[0022]

[0023]

[0024] Where i gd 、i gq are the d and q axis components of the GSC output current respectively; R g is the GSC output resistance; C represents the DC bus capacitance, U dcn Indicates the rated value of the DC bus voltage, Sn Indicates rated capacity.

[0025] Preferably, the step S2 adopts:

[0026] Step S2.1: Input the grid short-circuit ratio k SCR Numerical conversion to linear state space model of doubly fed wind turbine grid-connected system, calculate the steady-state equilibrium point under rated power, keep other controller parameters unchanged, and generate the K PSS 、T c and K c The state matrix A;

[0027] Step S2.2: Based on the current T c , K c and K PSS and based on the current T c , K c and the changed K PSS Solve the eigenvalue λ=α+jβ of the state matrix A, and ensure that the calculated eigenvalue real part α makes the current double-fed wind turbine grid-connected system in a critical stable state; output the current k SCR K PSS The stability limit value of

[0028] Step S2.3: Let k SCR =k SCR +Δk SCR , repeat the triggering steps S2.1 to S2.3 to obtain different grid short-circuit ratios k SCR K under PSS The stability limit value of k SCR Within the preset range.

[0029] Preferably, the step S2 adopts:

[0030] Step S2.4: Input the grid short-circuit ratio k SCR Numerical conversion to linear state space model of doubly fed wind turbine grid-connected system, calculate the steady-state equilibrium point under rated power, keep other controller parameters unchanged, and generate the K PSS 、T c and K c The state matrix A;

[0031] Step S2.5: Based on the current T c , K c and K PSS and based on the current T c , K PSS and the changed K cSolve the eigenvalue λ=α+jβ of the state matrix A, and ensure that the calculated eigenvalue real part α makes the current double-fed wind turbine grid-connected system in a critical stable state; output the current k SCR K c The stability limit value of

[0032] Step S2.6: Let k SCR =k SCR +Δk SCR , repeat the triggering steps S2.4 to S2.6 to obtain different grid short-circuit ratios k SCR K under c The stability limit value of k SCR Within the preset range.

[0033] Preferably, the step S2 adopts:

[0034] Step S2.7: Input the grid short-circuit ratio k SCR Numerical conversion to linear state space model of doubly fed wind turbine grid-connected system, calculate the steady-state equilibrium point under rated power, keep other controller parameters unchanged, and generate the K PSS 、T c and K c The state matrix A;

[0035] Step S2.8: Based on the current T c , K c and K PSS and based on the current K c , K PSS and the changed T c Solve the eigenvalue λ=α+jβ of the state matrix A, and ensure that the calculated eigenvalue real part α makes the current double-fed wind turbine grid-connected system in a critical stable state; output the current k SCR Lower T c The stability limit value of

[0036] Step S2.9: Let k SCR =k SCR +Δk SCR Repeat steps S2.7 to S2.9 to obtain different grid short-circuit ratios k SCR T below c The stability limit value of k SCR Within the preset range.

[0037] Preferably, the stabilization control coefficient K is calculated based on the inertia response rise time of the doubly fed wind turbine generator set. PSS Upper limit of

[0038] DC side voltage change Δu dcThe relationship between it and the grid voltage frequency change Δω1 is:

[0039]

[0040] in,

[0041]

[0042] Among them, x g is the total inductive reactance between the GSC output terminal and the grid; ω1 is the grid voltage angular frequency;

[0043] Considering that the rise time of the grid-connected doubly-fed wind turbine system is limited to t1, the approximate formula for the rise time of the second-order system is:

[0044]

[0045] Among them, t r is the active power rise time; ξ is the damping ratio of the second-order system; ω n is the undamped natural angular frequency of the second-order system;

[0046] Then the stabilizing control parameter K can be obtained PSS The design conditions are:

[0047] t r ≤t1.

[0048] Preferably, the inertia time constant of the self-synchronous voltage source doubly fed wind turbine is calculated, and the inertia controller gain K is obtained based on the mechanical and electrical allowable conditions of the doubly fed wind turbine. c The lower limit of

[0049] The inertia time constant of the inertia synchronous doubly fed generator set is:

[0050]

[0051] Among them, U dcn is the rated value of DC bus voltage; S n is the system rated apparent power; C is the DC bus capacitance;

[0052] The inertia time constant of the inertia synchronous doubly fed unit should not be less than the current time constant of the unit's rotating components, and its expression is:

[0053]

[0054] Among them, J WT Represents the moment of inertia of the wind wheel; ω wt Indicates the rated speed of the wind wheel; J M represents the moment of inertia of the generator; ω m Indicates the rated speed of the generator; HW Indicates the inertia time constant of the fan; P s Indicates the stator output active power, H s Indicates the current time constant of the rotating parts of the unit,

[0055] Then the inertia controller gain K can be obtained c The design conditions are:

[0056]

[0057] Preferably, the wind turbine generator set should be able to respond to the frequency conversion rate of the double-fed wind turbine generator grid-connected system according to the national standard, and the corresponding high-pass filter cutoff frequency is calculated to obtain the inertia controller time constant T c Upper limit of

[0058] In the inertia controller, a high-pass filter is used instead of a pure differentiator to detect u dc The rate of change of the corresponding high-pass filter expression is:

[0059]

[0060] The cutoff frequency of the high-pass filter is:

[0061]

[0062] Among them, T c Indicates the time constant of inertia transfer control, G HPF (s) represents the transfer function of the high-pass filter,

[0063] Assume that the high-pass filter frequency is γ min The gain of the frequency signal is less than a, and the time constant T of the inertia controller can be obtained. c The design formula is:

[0064]

[0065] According to the present invention, a self-synchronous voltage source doubly-fed wind turbine inertia response stabilization control system is provided, comprising:

[0066] Module M1: Establishing the linearized state space model of the doubly-fed wind turbine grid-connected system;

[0067] Module M2: Analyze the stabilizing control coefficient K based on the linearized state space model of the doubly fed wind turbine grid-connected system PSS , inertia control time constant T c and inertia control gain K c Stable regions under different grid short-circuit ratios;

[0068] Module M3: Stabilization control coefficient K based on the stable region under different grid short-circuit ratiosPSS , inertia control time constant T c and inertia control gain K c Realize the inertia response stability control and corresponding dynamic response characteristics of self-synchronous voltage source doubly fed wind turbines;

[0069] The linearized state space model of the doubly-fed wind turbine grid-connected system is a small signal mathematical model of the doubly-fed wind turbine grid-connected system obtained by adopting a small signal linearization modeling method at different working points.

[0070] Compared with the prior art, the present invention has the following beneficial effects:

[0071] 1. The present invention enables the voltage source doubly fed wind turbine to provide inertia support for the power grid and has good inertia response characteristics;

[0072] 2. The present invention realizes the self-synchronous voltage source doubly fed wind turbine generator set to achieve a frequency change rate <γ min The frequency event does not respond, but the frequency change rate ≥ γ min Frequency events can accurately respond to inertia;

[0073] 3. When a frequency disturbance event occurs in the power system, the double-fed wind turbine can provide the same inertia support to the power grid as a synchronous generator of equal capacity, and within the stable operation range of the system, as K c As the inertia time constant of the unit increases, the duration of power release of the unit is long and the amplitude is large;

[0074] 4. If the grid frequency increases (or decreases) by 0.5Hz, the DC bus voltage can track the frequency change in real time and the rise time is ≤30ms. The DC bus voltage rise time varies with K. PSS increases with the increase of

[0075] 5. The present invention realizes the stable operation of the "rotor side inertia transfer + grid side inertia synchronization" doubly fed wind turbine under weak grid conditions. The proposed control parameter design method can enable the unit to operate stably under a wide range of grid impedance changes. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0077] Figure 1 Design a flow chart for the inertia response control parameters.

[0078] Figure 2 This is the grid-side converter control block diagram.

[0079] Figure 3 This is the control block diagram of the rotor side converter.

[0080] Figure 4 Schematic diagram of the small signal mathematical model of the grid-side converter.

[0081] Figure 5 Schematic diagram of the small signal mathematical model of the rotor side converter.

[0082] Figure 6 Schematic diagram of the doubly fed wind turbine model. DETAILED DESCRIPTION

[0083] The present invention will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several changes and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0084] Example 1

[0085] According to the present invention, a method for stabilizing inertia response of a self-synchronous voltage source doubly-fed wind turbine generator system is provided, comprising:

[0086] Step S1: Establishing a linearized state space model of the doubly-fed wind turbine grid-connected system;

[0087] Step S2: Analyze the stabilizing control coefficient K based on the linearized state space model of the doubly fed wind turbine grid-connected system PSS , inertia control time constant T c and inertia control gain K c Stable regions under different grid short-circuit ratios;

[0088] Step S3: Stabilization control coefficient K based on the stable region under different grid short-circuit ratios PSS , inertia control time constant T c and inertia control gain K c Realize the inertia response stability control and corresponding dynamic response characteristics of self-synchronous voltage source doubly fed wind turbines;

[0089] The linearized state space model of the doubly-fed wind turbine grid-connected system is a small signal mathematical model of the doubly-fed wind turbine grid-connected system obtained by adopting a small signal linearization modeling method at different working points.

[0090] Specifically, the step S1 adopts: establishing a mathematical model of the self-synchronous voltage source doubly-fed wind turbine generator system connected to a weak grid and performing linearization to obtain a linearized state space model of the doubly-fed wind turbine generator system connected to the grid.

[0091] Specifically, the linearized state space model of the doubly-fed wind turbine grid-connected system includes: a linearized small signal mathematical model of the rotor-side converter current inner loop control loop and a linearized small signal mathematical model of the grid-side converter output current;

[0092] The linearized small signal mathematical model of the rotor-side converter current inner loop control loop adopts:

[0093]

[0094]

[0095]

[0096] Where ω1 is the synchronous electrical angular velocity; σ is the leakage reactance coefficient; k p2 and k p4 is the current inner loop proportional coefficient; X r is the rotor mutual inductance in the dq coordinate system; R r is the rotor resistance; i rd 、i rq are the dq axis components of the rotor current respectively; Δi rd , Δi rq are the small disturbance quantities of the dq axis components of the rotor current respectively; are the rotor current dq axis component command values ​​respectively; are the small disturbances of the dq-axis components of the rotor current reference value, respectively; x2 and x4 are the outputs of the integrators in the d-axis and q-axis current control loops; Δx2 and Δx4 are the small disturbances of the outputs of the integrators in the d-axis and q-axis current control loops, respectively; Δx1 and Δx3 represent the small disturbances of the outputs of the integrators in the active and reactive power control loops, respectively; Δx5 represents the small disturbance of the output of the integrator in the virtual inertia control link, and k i1 Indicates the active outer loop integral coefficient, k i2 Indicates the rotor d-axis current inner loop integral coefficient, k i3 Indicates the reactive outer loop integral coefficient, k i4 represents the rotor q-axis current inner loop integral coefficient, Indicates the small disturbance of the stator active reference value, ΔP s represents the small disturbance of stator active power, Indicates the small disturbance of the active power reference value, Indicates the small disturbance of the stator reactive power reference value, ΔQ s Represents the small disturbance of stator reactive power, T c Indicates the time constant of inertia transfer control, Δu dc represents the small disturbance of DC bus voltage, Δs represents the small disturbance of slip rate, H represents the generator inertia time constant, Ps (0) Indicates the steady-state value of stator active power, s (0) Indicates the steady-state value of the slip rate, X m and X s are the mutual inductance of stator and rotor and the self-inductance of stator in dq coordinate system respectively;

[0097] The linearized small signal mathematical model of the grid-side converter output current adopts:

[0098]

[0099]

[0100]

[0101]

[0102] Where i gd 、i gq are the d and q axis components of the GSC output current respectively; R g is the GSC output resistance; C represents the DC bus capacitance, U dcn Indicates the rated value of DC bus voltage, S n Indicates rated capacity.

[0103] Specifically, the step S2 adopts:

[0104] Step S2.1: Input the grid short-circuit ratio k SCR Numerical conversion to linear state space model of doubly fed wind turbine grid-connected system, calculate the steady-state equilibrium point under rated power, keep other controller parameters unchanged, and generate the K PSS 、T c and K c The state matrix A;

[0105] More specifically, based on the linearized state space model of the doubly fed wind turbine grid-connected system, the 12th-order state space equation of the doubly fed wind turbine grid-connected system is obtained:

[0106]

[0107] The state variable Δx is:

[0108] Δx=[Δu dc ΔδΔi rd Δi rq Δx1Δx2Δx3Δx4Δi gd Δi gq ΔsΔx5]

[0109] The characteristic value λ of the doubly fed wind power system based on the ITC-ISynC control strategy can be obtained by solving the following formula.

[0110] det(λI-A)=0

[0111] Where: I is the 12×12 identity matrix; λ is the eigenvalue; det is the function for finding the matrix determinant.

[0112]

[0113] Step S2.2: Based on the current T c , K c and K PSS and based on the current T c , K c and the changed K PSS Solve the eigenvalue λ=α+jβ of the state matrix A, and ensure that the calculated eigenvalue real part α makes the current double-fed wind turbine grid-connected system in a critical stable state; output the current k SCR K PSS The stability limit value of

[0114] Step S2.3: Let k SCR =k SCR +Δk SCR , repeat the triggering steps S2.1 to S2.3 to obtain different grid short-circuit ratios k SCR K under PSS The stability limit value of k SCR Within the preset range.

[0115] Specifically, the step S2 adopts:

[0116] Step S2.4: Input the grid short-circuit ratio k SCR Numerical conversion to linear state space model of doubly fed wind turbine grid-connected system, calculate the steady-state equilibrium point under rated power, keep other controller parameters unchanged, and generate the K PSS 、T c and K c The state matrix A;

[0117] Step S2.5: Based on the current T c , K c and K PSS and based on the current T c , K PSS and the changed K c Solve the eigenvalue λ=α+jβ of the state matrix A, and ensure that the calculated eigenvalue real part α makes the current double-fed wind turbine grid-connected system in a critical stable state; output the current k SCR K cThe stability limit value of

[0118] Step S2.6: Let k SCR =k SCR +Δk SCR , repeat the triggering steps S2.4 to S2.6 to obtain different grid short-circuit ratios k SCR K under c The stability limit value of k SCR Within the preset range.

[0119] Specifically, the step S2 adopts:

[0120] Step S2.7: Input the grid short-circuit ratio k SCR Numerical conversion to linear state space model of doubly fed wind turbine grid-connected system, calculate the steady-state equilibrium point under rated power, keep other controller parameters unchanged, and generate the K PSS 、T c and K c The state matrix A;

[0121] Step S2.8: Based on the current T c , K c and K PSS and based on the current K c , K PSS and the changed T c Solve the eigenvalue λ=α+jβ of the state matrix A, and ensure that the calculated eigenvalue real part α makes the current double-fed wind turbine grid-connected system in a critical stable state; output the current k SCR Lower T c The stability limit value of

[0122] Step S2.9: Let k SCR =k SCR +Δk SCR Repeat steps S2.7 to S2.9 to obtain different grid short-circuit ratios k SCR T below c The stability limit value of k SCR Within the preset range.

[0123] Specifically, based on the inertia response rise time of the doubly fed wind turbine generator set, the stabilization control coefficient K is calculated. PSS More specifically, it includes: setting the upper limit of the active power rise time; and then calculating K according to the approximate formula of the rise time. PSS The final range; Finally, the different grid short circuit ratio k SCR K under PSS The stability limit value and the currently calculated K PSS The final range of the intersection is taken and the output is K PSSThe final scope of

[0124] DC side voltage change Δu dc The relationship between it and the grid voltage frequency change Δω1 is:

[0125]

[0126] in,

[0127]

[0128] Among them, x g is the total inductive reactance between the GSC output terminal and the grid; ω1 is the grid voltage angular frequency;

[0129] Considering that the rise time of the grid-connected doubly-fed wind turbine system is limited to t1, the approximate formula for the rise time of the second-order system is:

[0130]

[0131] Among them, t r is the active power rise time; ξ is the damping ratio of the second-order system; ω n is the undamped natural angular frequency of the second-order system;

[0132] Then the stabilizing control parameter K can be obtained PSS The design conditions are:

[0133] t r ≤t1.

[0134] Specifically, the inertia time constant of the self-synchronous voltage source doubly fed wind turbine is calculated, and the inertia controller gain K is obtained based on the mechanical and electrical allowable conditions of the doubly fed wind turbine. c The lower limit of Kc is obtained; more specifically, it includes: according to the set doubly fed wind power system rotor moment of inertia, wind rotor rated speed, generator moment of inertia, generator rated speed, wind turbine inertia time constant and the steady-state value of stator output active power, the current time constant of the doubly fed unit rotating parts is obtained; according to the set doubly fed wind power system DC bus capacitance, DC voltage rated value and rated capacity, the inertia time constant of the inertia synchronous doubly fed wind turbine is obtained; and according to the inertia time constant of the inertia synchronous doubly fed unit should not be less than the current time constant of the rotating parts of the unit, the range of Kc is calculated. Finally, the above-mentioned different grid short-circuit ratios k are obtained. SCR K under c The intersection of the stability limit value and the currently calculated range of Kc is taken, and the final range of Kc is output.

[0135] The inertia time constant of the inertia synchronous doubly fed generator set is:

[0136]

[0137] Among them, U dcn is the rated value of DC bus voltage; S n is the system rated apparent power; C is the DC bus capacitance;

[0138] The inertia time constant of the inertia synchronous doubly fed unit should not be less than the current time constant of the unit's rotating components, and its expression is:

[0139]

[0140] Among them, J WT Represents the moment of inertia of the wind wheel; ω wt Indicates the rated speed of the wind wheel; J M represents the moment of inertia of the generator; ω m Indicates the rated speed of the generator; H W Indicates the inertia time constant of the fan; P s Indicates the stator output active power, H s Indicates the current time constant of the rotating parts of the unit,

[0141] Then the inertia controller gain K can be obtained c The design conditions are:

[0142]

[0143] Specifically, according to the national standard, the wind turbine should be able to respond to the frequency conversion rate of the double-fed wind turbine grid-connected system, and the corresponding high-pass filter cutoff frequency is calculated to obtain the inertia controller time constant T c More specifically, it includes: setting the minimum frequency change rate that the wind turbine should be able to respond to the system; calculating the range of Tc based on the cutoff frequency expression of the high-pass filter. Finally, the above-mentioned different grid short-circuit ratios k SCR T below c The intersection of the stability limit value and the currently calculated Tc range is taken to output the final range of Tc.

[0144] In the inertia controller, a high-pass filter is used instead of a pure differentiator to detect u dc The rate of change of the corresponding high-pass filter expression is:

[0145]

[0146] The cutoff frequency of the high-pass filter is:

[0147]

[0148] Among them, T c Indicates the time constant of inertia transfer control, G HPF(s) represents the transfer function of the high-pass filter,

[0149] Assume that the high-pass filter frequency is γ min The gain of the frequency signal is less than a, and the time constant T of the inertia controller can be obtained. c The design formula is:

[0150]

[0151] The inertia response stabilization control system for a self-synchronous voltage source doubly fed wind turbine provided by the present invention can be implemented using the steps and procedures of the inertia response stabilization control method for a self-synchronous voltage source doubly fed wind turbine provided by the present invention. Those skilled in the art can understand the inertia response stabilization control method for a self-synchronous voltage source doubly fed wind turbine as a preferred example of an inertia response stabilization control system for a self-synchronous voltage source doubly fed wind turbine.

[0152] Example 2

[0153] Example 2 is a preferred example of Example 1

[0154] This invention proposes a control parameter design method for the inertia response of a self-synchronous voltage source doubly fed wind turbine. This method enables the self-synchronous voltage source doubly fed wind turbine to have selective inertia support capabilities. Within the dead zone of grid frequency variation, the turbine does not perform inertia response. Outside the dead zone, the turbine exhibits good inertia response characteristics. When a frequency disturbance occurs in the power system, the doubly fed wind turbine can maintain its own stable operation while providing the grid with inertia support equivalent to that of a synchronous generator of equal capacity. Within the maximum inertia support range, the turbine's inertia time constant is freely adjustable. This also enables the self-synchronous voltage source doubly fed wind turbine to maintain stable operation over a wide range of grid impedance variations.

[0155] The present invention proposes a control parameter design method for the inertia response of a self-synchronous voltage source doubly fed wind turbine generator set, wherein a high-pass filter is set in the inertia transfer control loop of the rotor-side converter of the wind turbine generator set to detect the DC bus voltage u dc The grid-side converter of the wind turbine introduces a stability controller to improve the stability of the system. Figure 1 As shown, the specific design steps are as follows:

[0156] like Figures 2 to 6 As shown, step 1: establish a mathematical model for the self-synchronous voltage source doubly fed wind turbine generator system to be connected to the weak grid and perform linearization to obtain the small signal mathematical model of the system.

[0157] The small signal mathematical model of the rotor-side converter is as follows:

[0158]

[0159] Where x1 and x3 are the outputs of the integrators in the active and reactive power control loops; x2 and x4 are the outputs of the integrators in the d-axis and q-axis current control loops; x5 is the output of the integrator in the virtual inertia control link; P s * and is the maximum power tracking command value; P s and Q s Output active and reactive power to the stator; is the additional power; i rd 、i rq are the dq axis components of the rotor current respectively; are the rotor current dq axis component command values ​​respectively; u dc is the DC bus voltage; k i1 and k i3 k is the integral coefficient of the power outer loop; i2 and k i4 is the current inner loop integral coefficient; T c is the inertia control time constant; ω1 is the synchronous electrical angular velocity; σ is the leakage reactance coefficient; k p2 and k p4 is the current inner loop proportional coefficient; X r is the rotor mutual inductance in the dq coordinate system; R r is the rotor resistance; s is the generator slip rate; H is the generator inertia time constant; X m and X s are the mutual inductance between stator and rotor and the self-inductance of stator in the dq coordinate system respectively.

[0160] The small signal mathematical model of the grid-side converter is as follows:

[0161]

[0162] in,

[0163]

[0164] Where i gd 、i gq are the d and q axis components of the GSC output current respectively; R g is the resistance at the output of GSC; U is the amplitude of the modulation voltage vector; H C is the capacitor inertia time constant; k SCR is the short-circuit ratio of the power grid; U s is the stator voltage; K PSS is the proportional gain factor of the stabilizing control link.

[0165] Step 2: Analyze the stabilization control coefficient K based on the linearized small signal model of the system PSS, inertia control time constant T c and inertia control gain K c The stable area under different grid short-circuit ratios. The specific solution algorithm implementation steps are as follows: Input the grid short-circuit ratio k SCR Value, calculate the steady-state equilibrium point under rated power, keep other controller parameters unchanged, and generate PSS (T c or K c ) The state matrix A of the variable; change K PSS (T c or K c ) value, solve the eigenvalue of the state matrix A, and select the eigenvalue λ with the largest real part max =α max +jβ; if α max <0, then return to step II to continue solving; when α max >0 is just satisfied, the system is in a critical stable state, that is, k SCR K PSS (T c or K c ) stability limit, output the value and let k SCR =k SCR +Δk SCR , return to step Ⅰ to continue solving, k SCR ∈[1,10].

[0166] More specifically, it includes:

[0167] Step 21: Determine the short-circuit ratio k of different power grids SCR The stability domain of the lower Kpss;

[0168] Step 22: Determine the short-circuit ratio k of different power grids SCR The stability domain of the lower Kc;

[0169] Step 23: Determine the short-circuit ratio k of different power grids SCR The stability domain of lower Tc;

[0170] Step 21:

[0171] Step 211: Set the grid short-circuit ratio k SCR Initial value, wind speed value, find the stable working point;

[0172] Step 212: Calculate the state matrix A based on the steady-state equilibrium point;

[0173] Step 213: Calculate the characteristic root according to the initial values ​​of Tc, Kc, and Kpss;

[0174] Step 214: Change the value of Kpss and calculate the characteristic root;

[0175] Step 215: Determine whether the characteristic root is on the right plane. If so, proceed to step 216; if not, return to step 214.

[0176] Step 216: Obtain a Kpss range under a fixed Kscr;

[0177] Step 217: Change the value of Kscr and determine whether Kscr is less than 1. If the condition is met, go to step 218; if not, return to step 211;

[0178] Step 218: Output different grid short-circuit ratios k SCR The stability domain of Kpss.

[0179] Step 22:

[0180] Step 221: Set the grid short-circuit ratio k SCR Initial value, wind speed value, find the stable working point;

[0181] Step 222: Calculate the state matrix A based on the steady-state equilibrium point;

[0182] Step 223: Calculate the characteristic root according to the initial values ​​of Tc, Kc, and Kpss;

[0183] Step 224: Change the value of Kc and calculate the characteristic root;

[0184] Step 225: Determine whether the characteristic root is on the right plane. If so, proceed to step 226; if not, return to step 224.

[0185] Step 226: Obtain a Kc range under a fixed Kscr;

[0186] Step 227: Change the value of Kscr and determine whether Kscr is less than 1. If the condition is met, go to step 228; if not, return to step 221;

[0187] Step 228: Output different grid short-circuit ratios k SCR The stability domain of Kc.

[0188] Step 23:

[0189] Step 231: Set the grid short circuit ratio k SCR Initial value, wind speed value, find the stable working point;

[0190] Step 232: Calculate the state matrix A based on the steady-state equilibrium point;

[0191] Step 233: Calculate the characteristic root according to the initial values ​​of Tc, Kc, and Kpss;

[0192] Step 234: Change the value of Tc and calculate the characteristic root;

[0193] Step 235: Determine whether the characteristic root is on the right plane. If so, proceed to step 236; if not, return to step 234.

[0194] Step 236: Obtain a Tc range under a certain fixed Kscr;

[0195] Step 237: Change the value of Kscr and determine whether Kscr is less than 1. If the condition is met, go to step 238; if not, return to step 231;

[0196] Step 238: Output different grid short-circuit ratios k SCR The stability domain of lower Tc.

[0197] According to the national standard, the wind turbine should be able to respond to the frequency conversion rate of the system, and calculate the corresponding high-pass filter cutoff frequency, and find the inertia controller time constant T c The specific process is as follows:

[0198] In the inertia controller, a high-pass filter is used instead of a pure differentiator to detect u dc The rate of change of the corresponding high-pass filter expression is:

[0199]

[0200] The cutoff frequency of the high-pass filter is:

[0201]

[0202] The national standard "GB / T 36994-2018 Wind Turbine Grid Adaptability Test Procedure" stipulates that when the rate of change of the grid frequency exceeds the minimum value γmin (recommended 0.3Hz / s), the wind turbine should be able to respond to the system's frequency change rate, that is, the virtual inertia controller of the self-synchronous voltage source wind turbine should be able to filter out frequency signals with a change rate less than γmin.

[0203] Assume that the high-pass filter frequency is γ min The gain of the frequency signal is less than a, and the time constant T of the inertia controller can be obtained. c The design formula is:

[0204]

[0205] (4) Calculate the inertia time constant of the self-synchronous voltage source doubly fed wind turbine generator set, considering the limitations of the doubly fed generator set's own mechanical and electrical allowable conditions, and calculate the inertia controller gain K c The lower limit of the inertia time constant of the doubly fed generator is usually determined by referring to a synchronous generator of the same capacity. The specific process is as follows:

[0206] The inertia time constant of the inertia synchronous doubly fed generator set is:

[0207]

[0208] Where U dcn is the rated value of DC bus voltage; S n is the rated apparent power of the system; C is the DC bus capacitance.

[0209] The inertia time constant of the inertia synchronous doubly fed unit should not be less than the current time constant of the unit's rotating components, and its expression is:

[0210]

[0211] Where: J WT Represents the moment of inertia of the wind wheel; ω wt Indicates the rated speed of the wind wheel; J M represents the moment of inertia of the generator; ω m Indicates the rated speed of the generator; H W Indicates the inertia time constant of the fan.

[0212] Then the inertia controller gain K can be obtained c The design conditions are:

[0213]

[0214] (5) Rationally design the inertia response rise time of the doubly fed wind turbine generator set and calculate the stabilization control coefficient K PSS The specific process is as follows:

[0215] K PSS The physical meaning is that the DC voltage maps the damping coefficient of the grid frequency in real time, K PSS A larger value can suppress the oscillation of the DC voltage response process when the grid frequency changes, but it will also affect the tracking performance of the DC voltage to the grid frequency and increase the response time of the inertia response.

[0216] DC side voltage change Δu dc The relationship between it and the grid voltage frequency change Δω1 is:

[0217]

[0218] in,

[0219]

[0220] Where: x g is the total inductive reactance between the GSC output terminal and the grid; ω1 is the grid voltage angular frequency.

[0221] Considering that the rise time of the system is limited to 30ms, the approximate formula for the rise time of the second-order system is:

[0222]

[0223] Where: t r is the active power rise time; ξ is the damping ratio of the second-order system; ω n is the undamped natural angular frequency of the second-order system.

[0224] Then the stabilizing control parameter K can be obtained PSS The design conditions are:

[0225] t r ≤0.03

[0226] Those skilled in the art will appreciate that, in addition to implementing the system, device, and various modules provided by the present invention in purely computer-readable program code, it is entirely possible to implement the same program in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, embedded microcontrollers, and the like by logically programming the method steps. Therefore, the system, device, and various modules provided by the present invention can be considered a hardware component, and the modules included therein for implementing various programs can also be considered structures within the hardware component; the modules for implementing various functions can also be considered both software programs for implementing the method and structures within the hardware component.

[0227] The above describes specific embodiments of the present invention. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. The embodiments of this application and the features in the embodiments may be combined with each other in any manner unless there is a conflict.

Claims

1. A method for stabilizing inertia response of a self-synchronous voltage source doubly-fed wind turbine generator system, characterized in that: include: Step S1: Establishing a linearized state space model of the doubly-fed wind turbine grid-connected system; Step S2: Analyze the stabilizing control coefficient K based on the linearized state space model of the doubly fed wind turbine grid-connected system PSS , inertia control time constant T c and inertia control gain K c Stable regions under different grid short-circuit ratios; Step S3: Stabilization control coefficient K based on the stable region under different grid short-circuit ratios PSS , inertia control time constant T c and inertia control gain K c Realize the inertia response stability control and corresponding dynamic response characteristics of self-synchronous voltage source doubly fed wind turbines; The linearized state space model of the doubly-fed wind turbine grid-connected system is obtained by using a small signal linear modeling method at different operating points to obtain a small signal mathematical model of the doubly-fed wind turbine grid-connected system; Calculate the stabilization control coefficient K based on the inertia response rise time of the doubly fed wind turbine PSS Upper limit of DC side voltage change Δu dc The relationship between it and the grid voltage frequency change Δω1 is: in, Among them, x g is the total inductive reactance between the GSC output terminal and the grid; ω1 is the grid voltage angular frequency; Considering that the rise time of the grid-connected doubly-fed wind turbine system is limited to t1, the approximate formula for the rise time of the second-order system is: Among them, t r is the active power rise time; ξ is the damping ratio of the second-order system; ω n is the undamped natural angular frequency of the second-order system; Then the stabilizing control parameter K can be obtained PSS The design conditions are: t r ≤t1; Determine the frequency conversion rate that the wind turbine should be able to respond to the double-fed wind turbine grid-connected system, calculate the corresponding high-pass filter cutoff frequency, and find the inertia controller time constant T c Upper limit of In the inertia controller, a high-pass filter is used instead of a pure differentiator to detect u dc The rate of change of the corresponding high-pass filter expression is: The cutoff frequency of the high-pass filter is: Among them, T c Indicates the time constant of inertia transfer control, G HPF (s) represents the transfer function of the high-pass filter, Assume that the high-pass filter frequency is γ min The gain of the frequency signal is less than a, and the time constant T of the inertia controller can be obtained. c The design formula is:

2. The inertia response stabilization control method of a self-synchronous voltage source doubly-fed wind turbine generator system according to claim 1, characterized in that: The step S1 adopts: establishing a mathematical model of the self-synchronous voltage source doubly-fed wind turbine generator system connected to a weak grid and performing linearization to obtain a linearized state space model of the doubly-fed wind turbine generator system connected to the grid.

3. The inertia response stabilization control method of a self-synchronous voltage source doubly-fed wind turbine generator system according to claim 2, characterized in that: The linearized state space model of the doubly-fed wind turbine grid-connected system includes: a linearized small signal mathematical model of the rotor-side converter current inner loop control loop and a linearized small signal mathematical model of the grid-side converter output current; The linearized small signal mathematical model of the rotor-side converter current inner loop control loop adopts: Where ω1 is the synchronous electrical angular velocity; σ is the leakage reactance coefficient; k p2 and k p4 is the current inner loop proportional coefficient; X r is the rotor mutual inductance in the dq coordinate system; R r is the rotor resistance; i rd 、i rq are the dq axis components of the rotor current respectively; Δi rd , Δi rq are the small disturbance quantities of the dq axis components of the rotor current respectively; are the rotor current dq axis component command values ​​respectively; are the small disturbances of the dq-axis components of the rotor current reference value, respectively; x2 and x4 are the outputs of the integrators in the d-axis and q-axis current control loops; Δx2 and Δx4 are the small disturbances of the outputs of the integrators in the d-axis and q-axis current control loops, respectively; Δx1 and Δx3 represent the small disturbances of the outputs of the integrators in the active and reactive power control loops, respectively; Δx5 represents the small disturbance of the output of the integrator in the virtual inertia control link, and k i1 Indicates the active outer loop integral coefficient, k i2 Indicates the rotor d-axis current inner loop integral coefficient, k i3 Indicates the reactive outer loop integral coefficient, k i4 represents the rotor q-axis current inner loop integral coefficient, Indicates the small disturbance of the stator active reference value, ΔP s represents the small disturbance of stator active power, Indicates the small disturbance of the active power reference value, Indicates the small disturbance of the stator reactive power reference value, ΔQ s Represents the small disturbance of stator reactive power, T c Indicates the time constant of inertia transfer control, Δu dc It represents the small disturbance of DC bus voltage, Δs represents the small disturbance of slip rate, H represents the generator inertia time constant, Indicates the steady-state value of stator active power, s (0) Indicates the steady-state value of the slip rate, X m and X s are the mutual inductance of stator and rotor and the self-inductance of stator in dq coordinate system respectively; The linearized small signal mathematical model of the grid-side converter output current adopts: Where i gd 、i gq are the d and q axis components of the GSC output current respectively; R g is the GSC output resistance; C represents the DC bus capacitance, U dcn Indicates the rated value of DC bus voltage, S n Indicates rated capacity.

4. The inertia response stabilization control method of a self-synchronous voltage source doubly-fed wind turbine generator system according to claim 1, characterized in that: The step S2 adopts: Step S2.1: Input the grid short-circuit ratio k SCR Numerical conversion to linear state space model of doubly fed wind turbine grid-connected system, calculate the steady-state equilibrium point under rated power, keep other controller parameters unchanged, and generate the K PSS 、T c and K c The state matrix A; Step S2.2: Based on the current T c , K c and K PSS and based on the current T c , K c and the changed K PSS Solve the eigenvalue λ=α+jβ of the state matrix A, and ensure that the calculated eigenvalue real part α makes the current double-fed wind turbine grid-connected system in a critical stable state; output the current k SCR K PSS The stability limit value of Step S2.3: Let k SCR =k SCR +Δk SCR , repeat the triggering steps S2.1 to S2.3 to obtain different grid short-circuit ratios k SCR K under PSS The stability limit value of k SCR Within the preset range.

5. The inertia response stabilization control method of a self-synchronous voltage source doubly-fed wind turbine generator system according to claim 1, characterized in that: The step S2 adopts: Step S2.4: Input the grid short-circuit ratio k SCR Numerical conversion to linear state space model of doubly fed wind turbine grid-connected system, calculate the steady-state equilibrium point under rated power, keep other controller parameters unchanged, and generate the K PSS 、T c and K c The state matrix A; Step S2.5: Based on the current T c , K c and K PSS and based on the current T c , K PSS and the changed K c Solve the eigenvalue λ=α+jβ of the state matrix A, and ensure that the calculated eigenvalue real part α makes the current double-fed wind turbine grid-connected system in a critical stable state; output the current k SCR K c The stability limit value of Step S2.6: Let k SCR =k SCR +Δk SCR , repeat the triggering steps S2.4 to S2.6 to obtain different grid short-circuit ratios k SCR K under c The stability limit value of k SCR Within the preset range.

6. The inertia response stabilization control method of a self-synchronous voltage source doubly-fed wind turbine generator system according to claim 1, characterized in that: The step S2 adopts: Step S2.7: Input the grid short-circuit ratio k SCR Numerical conversion to linear state space model of doubly fed wind turbine grid-connected system, calculate the steady-state equilibrium point under rated power, keep other controller parameters unchanged, and generate the K PSS 、T c and K c The state matrix A; Step S2.8: Based on the current T c , K c and K PSS and based on the current K c , K PSS and the changed T c Solve the eigenvalue λ=α+jβ of the state matrix A, and ensure that the calculated eigenvalue real part α makes the current double-fed wind turbine grid-connected system in a critical stable state; output the current k SCR Lower T c The stability limit value of Step S2.9: Let k SCR =k SCR +Δk SCR Repeat steps S2.7 to S2.9 to obtain different grid short-circuit ratios k SCR T below c The stability limit value of k SCR Within the preset range.

7. The inertia response stabilization control method of a self-synchronous voltage source doubly-fed wind turbine generator system according to claim 1, characterized in that: Calculate the inertia time constant of the self-synchronous voltage source doubly fed wind turbine and obtain the inertia controller gain K based on the mechanical and electrical allowable conditions of the doubly fed wind turbine. c The lower limit of The inertia time constant of the inertia synchronous doubly fed generator set is: Among them, U dcn is the rated value of DC bus voltage; S n is the system rated apparent power; C is the DC bus capacitance; The inertia time constant of the inertia synchronous doubly fed unit should not be less than the current time constant of the unit's rotating components, and its expression is: Among them, J WT Represents the moment of inertia of the wind wheel; ω wt Indicates the rated speed of the wind wheel; J M represents the moment of inertia of the generator; ω m Indicates the rated speed of the generator; H W Indicates the inertia time constant of the fan; P s Indicates the stator output active power, H s Indicates the current time constant of the rotating parts of the unit, Then the inertia controller gain K can be obtained c The design conditions are:

8. A self-synchronous voltage source doubly fed wind turbine inertia response stability control system, characterized in that: The inertia response stabilization control method of a self-synchronous voltage source doubly-fed wind turbine generator system according to any one of claims 1 to 7 comprises: Module M1: Establishing the linearized state space model of the doubly-fed wind turbine grid-connected system; Module M2: Analyze the stabilizing control coefficient K based on the linearized state space model of the doubly fed wind turbine grid-connected system PSS , inertia control time constant T c and inertia control gain K c Stable regions under different grid short-circuit ratios; Module M3: Stabilization control coefficient K based on the stable region under different grid short-circuit ratios PSS , inertia control time constant T c and inertia control gain K c Realize the inertia response stability control and corresponding dynamic response characteristics of self-synchronous voltage source doubly fed wind turbines; The linearized state space model of the doubly-fed wind turbine grid-connected system is a small signal mathematical model of the doubly-fed wind turbine grid-connected system obtained by adopting a small signal linearization modeling method at different working points.

Images