Enhanced hybrid synchronous control method for grid-forming type doubly-fed wind power converter

Abstract

The invention discloses an enhanced hybrid synchronous control method for a grid-forming doubly-fed wind power converter, and belongs to the field of electrical engineering. The control method comprises enhanced hybrid synchronous control based on a self-adaptive integrator, reactive-voltage droop control and stator voltage and rotor current double-closed-loop control. In order to solve the problem that the resynchronization stability problem of the grid-forming type doubly-fed wind power converter cannot be solved when a traditional grid-forming type converter depends on a hybrid synchronization control algorithm of virtual impedance and is faced with fault scenes such as power grid voltage drop and the like, an existing parameter design method is not suitable for a grid-forming type doubly-fed wind power converter system any more. According to the invention, the voltage synchronization loop based on the adaptive integrator is introduced, so that existence of a stable working point during a fault period is powerfully ensured. And the built adaptive integrator parameter design principle can ensure the synchronous and stable adaptive adjustment capability of the doubly-fed wind power converter under different fault working conditions.

Description

Technical Field

[0001] The invention belongs to the field of electrical engineering, and in particular relates to an enhanced hybrid synchronous control method for a grid-type doubly-fed wind power converter. Background Art

[0002] As my country's energy structure continues to optimize, the proportion of new energy sources is gradually increasing, and the penetration rate of doubly-fed wind power generation is constantly increasing. As an important link between doubly-fed wind turbines and the power grid, the control structure of the converter is crucial to the stable operation of the system. Different from the passive following of grid-following control, grid-building control has better characteristics in synchronization stability.

[0003] Hybrid synchronous control (HSC) is a kind of synchronous control method for grid-forming converters. It was originally proposed to improve the operating stability of grid-forming converter control systems under different short-circuit ratio grids. In the article "Lima LAM, Watanabe EH. Hybrid Control Scheme for VSC Presenting Both Grid-Forming and Grid-Following Capabilities[J]. IEEE Transactions on Power Delivery, 2022, 37(6): 4570-4581." published in IEEE Transactions on Power Delivery in 2022, the synchronous loop designed is a weighted fusion of power synchronization and voltage synchronization, and a feedforward channel for active power control is introduced between the voltage controller and the current controller of the inner voltage loop, so that the grid-forming converter control system, which originally has a single voltage source characteristic, presents an adjustable port output characteristic that integrates the voltage source and current source characteristics. This implementation method of mixing the voltage source characteristic and the current source characteristic is called hybrid synchronous control of the converter.

[0004] Based on the basic idea of ​​hybrid synchronous control, scholars at home and abroad have proposed a series of control structures with similar functions. For example, in the article "Han F, Zhang X, Li M, et al. Stability Control for Grid-Connected Inverters Based on Hybrid-Mode of Grid-Following and Grid-Forming[J]. IEEE Transactions on Industrial Electronics, 2023, Early Access. Doi: 10.1109 / TIE.2023.3335325." published in the IEEE Transactions on Power Electronics in 2023, the characteristics of the voltage source and the current source are fused by constructing two sets of parallel and independent control subsystems in a single converter system and performing modulation weighting in the converter wave generation link.

[0005] The above research work on hybrid synchronous control focuses on small disturbance stability problems, and focuses on solving the control stability problem of grid-connected converter systems caused by large fluctuations in grid impedance under the background of high proportion of renewable energy generation. Research shows that the integration of power synchronization and voltage synchronization in hybrid synchronous control is not only conducive to improving the robust operation capability of the grid-connected converter system when the short-circuit ratio changes, but its hybrid voltage synchronization link can also be equivalent to the damping winding of the synchronous generator, providing the ability to limit the power angle movement under grid voltage faults.

[0006] "Liu T, Wang X. Physical Insight Into Hybrid-Synchronization-Controlled Grid-Forming Inverters Under Large Disturbances [J]. IEEE Transactions on Power Electronics, 2022, 37(10): 11475-11480." ("Physical Perspective of Hybrid Synchronization-Controlled Grid-Forming Inverters Under Large Disturbances Conditions"), published in the 2022 IEEE Transactions on Power Electronics, proposes that for the grid-forming converter system, the weak damping configuration of its active-synchronous loop is one of the main reasons for the overshoot and instability of the power angle under grid voltage faults. Therefore, it uses a second-order active controller based on virtual synchronous control in hybrid synchronous control, designs a special damping loop, and enhances the damping effect of the system synchronization angle under grid faults. However, it has the following shortcomings for grid-forming doubly fed wind power converters:

[0007] (1) The system relies heavily on the virtual impedance algorithm to provide stable and continuous correction for the active power command and system damping. However, the virtual impedance link increases the equivalent output impedance of the system, resulting in a decrease in the active power output limit of the system in the sense of control, which reduces the power generation efficiency.

[0008] (2) The optimization control is still based on improving the current limiting strategy, but does not provide a new stable operating point for the system to achieve stable control of the system during the resynchronization process.

[0009] (3) Compared with the grid-type converter, the resynchronization process of the grid-type doubly-fed wind power converter is affected by both the power control loop and the internal voltage control loop. The effectiveness of the existing synchronization stability improvement method based on the grid-type converter needs to be reconsidered when solving the synchronization stability problem of the grid-type doubly-fed wind power converter.

[0010] The Chinese patent document CN115579966A published on January 6, 2023, "A control method for a grid-type doubly-fed wind turbine based on hybrid synchronization", designs a DC voltage synchronous grid-type control scheme for the grid-side converter of the doubly-fed wind turbine, and realizes the autonomous grid-type operation of the doubly-fed wind turbine. The rotor-side converter and the grid-side converter participate in actively supporting the voltage / frequency of the power grid at the same time, and do not rely on the phase-locked loop for synchronization during operation, which improves its stability under weak power grids. Its shortcomings are:

[0011] (1) The hybrid synchronous control scheme adopted is for the rotor-side converter and the grid-side converter. The synchronous stability of the rotor-side converter with the largest active output has not been studied and analyzed.

[0012] (2) This method is limited to the analysis of the synchronization stability of doubly-fed wind turbines under small signal conditions, and does not involve the study of the synchronization stability under large transient disturbances.

[0013] (3) There are no clear design principles and selection criteria for the tuning and design of synchronous controller parameters.

[0014] In summary, the prior art has the following problems:

[0015] (1) Since the resynchronization process of the grid-type doubly-fed wind power converter is affected by the power control loop and the internal voltage control loop, and the grid-type converter only considers the synchronization instability problem dominated by the power loop. The existing synchronization stability improvement method based on the grid-type converter cannot solve the resynchronization stability problem of the grid-type doubly-fed wind power converter, so a new control method needs to be designed.

[0016] (2) In the existing hybrid synchronous control method of grid-connected converters, a virtual impedance algorithm is relied on to make a stable and continuous deviation between the voltage angle and the synchronization angle of the grid-connected point, so as to achieve a stable and continuous correction of the active power command and system damping. However, the virtual impedance link increases the equivalent output impedance of the system, causing the voltage source characteristics of the grid-connected point to shift, and the active output limit of the system in the sense of control is reduced, which is not conducive to ensuring the existence of a stable working point during a fault.

[0017] (3) When the hybrid synchronous control method was first proposed, it was used to optimize the damping characteristics of the grid-type converter based on the second-order active power controller, which can improve the power angle overshoot phenomenon caused by improper configuration of virtual inertia and virtual damping. However, for the grid-type doubly-fed wind power converter system using a first-order active power controller (droop control), the hybrid control method loses the original damping optimization goal. Therefore, the existing parameter design method is no longer applicable to the grid-type doubly-fed wind power converter system. Summary of the invention

[0018] The technical problem to be solved by the present invention is the shortcomings of the above-mentioned prior art. An enhanced hybrid synchronous control method for a grid-type doubly-fed wind power converter is proposed. The enhanced hybrid synchronous control method (EHSC) adds a voltage synchronization loop based on an adaptive integrator, establishes an adaptive integrator parameter design principle, and ensures the adaptive adjustment capability of the synchronous stability of the doubly-fed wind power converter under different fault conditions.

[0019] To achieve the above-mentioned object of the invention, the present invention provides a method for enhancing hybrid synchronous control of a grid-type doubly-fed wind power converter. The topological structure of the doubly-fed wind power converter to which the control method is applied includes a DC power supply, a main inverter, a doubly-fed wind turbine generator, a line impedance and a three-phase power grid connected in series in sequence. The steps of the control method are as follows:

[0020] Step 1: Collect the three-phase voltage u of the doubly-fed wind turbine generator stator sa ,u sb ,u sc and the three-phase current i of the stator sa ,i sb ,i sc , and the dq axis stator voltage u is obtained by coordinate transformation sd ,u sq and dq axis stator current i sd ,i sq ; Collect the three-phase current i of the doubly-fed wind turbine generator rotor ra ,i rb ,i rc and the rotor electrical angular velocity θ r , and the dq-axis rotor current i is obtained by coordinate transformation rd ,i rq ;

[0021] Step 2: First, according to the dq axis stator voltage u sd ,u sq and dq axis stator current i sd ,i sq , calculate the stator output active power p and stator output reactive power q of the doubly-fed wind turbine generator, and then perform low-pass filtering to calculate the active power P after the low-pass filter and the reactive power Q after the low-pass filter;

[0022] Step 3: Collect the grid point angle θ pcc , the enhanced hybrid synchronous control equation based on adaptive integrator is constructed, and the output frequency ω of the doubly fed wind power converter and the resynchronization angle θ of the grid-type doubly fed wind power converter are calculated. ref ;

[0023] The expression of the enhanced hybrid synchronous control equation based on the adaptive integrator is:

[0024]

[0025] In the formula, K P is the active droop coefficient, ω0 is the rated frequency, P ref is the active power reference value, K P,VBS To enhance the proportionality factor of the hybrid synchronous controller, V pcc is the effective value of the grid connection point voltage, KI,VBS is the adaptive integration coefficient of the adaptive integrator, s is the Laplace operator;

[0026] Step 4: Calculate the stator voltage amplitude U s , And as the d-axis stator voltage reference value, U ref is the voltage reference value, Q ref is the reactive power reference value, K q is the droop proportional coefficient;

[0027] Step 5, calculate the q-axis deviation r1 and d-axis deviation r2, r1 = 0-u sq , r2=U s -u sd , and input into the PI regulator of the stator voltage outer loop for processing, and the output is the dq axis rotor current command i rdref ,i rqref ; Calculate the d-axis rotor current command i rdref and the d-axis rotor current i rd The deviation between the q-axis rotor current command i rqref and the q-axis rotor current i rq The deviation between them is input into the PI regulator of the rotor current inner loop for processing, and the output is the dq axis rotor voltage command u rd_ref ,u rq_ref ;

[0028] Step 6: Set the dq axis rotor voltage command u rd_ref ,u rq_ref After the inverse coordinate transformation, the three-phase modulation wave U of the bridge arm voltage of the main inverter is obtained. ma ,U mb ,U mc , and then after modulation by the PWM link, the switch control signal s in the main inverter is generated a ,s b ,s c , to achieve stable control of the doubly-fed wind power converter.

[0029] Preferably, the calculation formulas for the stator output active power p and the stator output reactive power q of the doubly-fed wind turbine generator in step 2 are respectively:

[0030]

[0031] The calculation formula of the active power P after the low-pass filter and the reactive power Q after the low-pass filter is:

[0032]

[0033] In the formula, ω f is the cutoff frequency of the low-pass filter.

[0034] Preferably, the adaptive integral coefficient K of the adaptive integrator in step 3 is I,VBS is determined as follows:

[0035] Step 3.1, let the adaptive integral coefficient K I,VBS satisfy:

[0036]

[0037] Among them, K I,0 is the reference value of adaptive integration, V pcc,f is the voltage amplitude after the fault, V N is the rated value of the grid connection point voltage, K t is the adjustable gain, and the adjustable gain K t satisfy:

[0038]

[0039] In the formula, K t,0 The adjustable gain K t The benchmark value, k SCR is the short-circuit ratio of the power grid, P N is the rated active power, e is the natural constant;

[0040] The reference value K of the adaptive integral I,0 and the adjustable gain K t The reference value K t,0 is a parameter to be determined;

[0041] Step 3.2: Introduce the resynchronization angle θ of the grid-connected double-fed wind power converter when there is no control method ref Minimum acceleration time required for divergence The shortest acceleration time satisfy:

[0042]

[0043] In the formula, θ N is the rated active power P N The corresponding steady-state synchronization angle;

[0044] Introduce the q-axis component grid-connected point voltage u within the synchronization time Δt q The average value of the change The average satisfy:

[0045]

[0046] In the formula, t0 represents the grid voltage drop time;

[0047] Step 3.3, let P ref =P N , P = 0, the reference value K of the adaptive integral I,0 The calculation formula is:

[0048]

[0049] make P ref =P N ,P=0、V pcc,f =0, adjustable gain K t The reference value K t,0 The calculation formula is:

[0050]

[0051] The reference value K of the adaptive integral calculated in step 3.3 is I,0 and adjustable gain K t The reference value K t,0 Substituting into step 3.1, we get the adaptive integral coefficient K of the adaptive integrator: I,VBS .

[0052] Preferably, the dq axis rotor current instruction i in step 5 is rdref ,i rqref and dq axis rotor voltage command u rd_ref ,u rq_ref The calculation formulas are:

[0053]

[0054] In the formula, K pi is the proportional coefficient of the PI regulator of the rotor current inner loop, K ii K is the integral coefficient of the PI regulator of the rotor current inner loop, pu is the proportional coefficient of the PI regulator of the stator voltage outer loop, K iu are the proportional coefficient and integral coefficient of the PI regulator of the stator voltage outer loop.

[0055] Compared with the prior art, the present invention has the following beneficial effects:

[0056] 1. Aiming at the differences between grid-type converter and grid-type doubly-fed wind power converter in the resynchronization control process, the enhanced hybrid synchronization control method based on adaptive integrator adopted by the present invention solves the transient damping problem required for the resynchronization process, provides a new convergent working point when the original system does not have a stable working point, and effectively suppresses the divergence of the system synchronization angle and power angle during the fault period. The stability of the grid-type doubly-fed wind power converter in the resynchronization process is improved.

[0057] 2. The enhanced hybrid synchronous control method proposed in the present invention can realize the correction of active power command and system damping stability and continuity without relying on the virtual impedance algorithm. This effectively reduces the equivalent output impedance of the system, ensures the voltage source characteristics of the grid-connected double-fed wind power converter at the grid connection point, improves the active power output limit of the system in the sense of control, and is conducive to ensuring the existence of a stable working point during a fault.

[0058] 3. The present invention fully considers the adaptability of control parameters under different grid short-circuit ratios, grid voltage drop depths and active output levels before faults, overcomes the problem of unclear design of traditional control parameters, establishes a clear adaptive integral parameter design principle, and realizes efficient and stable operation of the grid-type doubly-fed wind power converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 It is the overall control diagram of the method of the present invention;

[0060] Figure 2 This is a structural diagram of the enhanced hybrid synchronous control based on the adaptive integrator in the present invention;

[0061] Figure 3 It is a reactive power-voltage droop control structure diagram in the present invention;

[0062] Figure 4 This is a structural diagram of the stator voltage and rotor current double closed-loop control in the present invention;

[0063] Figure 5 It is a transient stability boundary diagram of the grid-type doubly-fed wind power converter in the present invention;

[0064] Figure 6 This is a simulation diagram when using HSC synchronous control in the present invention;

[0065] Figure 7 This is a simulation diagram when using EHSC synchronous control in the present invention; DETAILED DESCRIPTION

[0066] The specific implementation modes of the present invention will be further described in detail below in conjunction with the accompanying drawings.

[0067] Figure 1 This is the overall control diagram of the method of the present invention. Figure 1 It can be seen that the present invention provides an enhanced hybrid synchronous control method for a grid-type doubly-fed wind power converter. The topological structure involved in the doubly-fed wind power converter using this control method includes a DC power supply, a main inverter, a doubly-fed wind turbine generator, a line impedance and a three-phase power grid connected in series in sequence.

[0068] exist Figure 1 DFIG is a doubly fed wind turbine generator, U dcis the voltage value at the DC power supply, L g is the inductance value in the line impedance, R g is the resistance value in the line impedance. In the present embodiment, R g =0.65mH, L g =0.01Ω.

[0069] In this embodiment, the doubly-fed wind turbine generator is a wound-rotor induction motor, and its rated parameters are: rated speed 1200 r / min, stator rated voltage 380 V, rotor rated voltage 1070 V, stator rated current 13.9 A, rotor rated current 6.8 A, pole pair number 3, stator resistance R s =0.69Ω, rotor resistance R r =0.59Ω, stator inductance L s =0.0748H, rotor inductance L r =0.0768H.

[0070] Depend on Figure 1 It can be seen that the control method of the present invention comprises the following steps:

[0071] Step 1: Collect the three-phase voltage u of the doubly-fed wind turbine generator stator sa ,u sb ,u sc and the three-phase current i of the stator sa ,i sb ,i sc , and the dq axis stator voltage u is obtained by coordinate transformation sd ,u sq and dq axis stator current i sd ,i sq ; Collect the three-phase current i of the doubly-fed wind turbine generator rotor ra ,i rb ,i rc and the rotor electrical angular velocity θ r , and the dq-axis rotor current i is obtained by coordinate transformation rd ,i rq .

[0072] Step 2: First, according to the dq axis stator voltage u sd ,u sq and dq axis stator current i sd ,i sq , the stator output active power p and stator output reactive power q of the doubly fed wind turbine generator are calculated, and then low-pass filtering is performed to calculate the active power P after the low-pass filter and the reactive power Q after the low-pass filter.

[0073] In this embodiment, the calculation formulas for the stator output active power p and the stator output reactive power q of the doubly-fed wind turbine generator are respectively:

[0074]

[0075] The calculation formula of the active power P after the low-pass filter and the reactive power Q after the low-pass filter is:

[0076]

[0077] In the formula, ω f is the cutoff frequency of the low-pass filter.

[0078] In this embodiment, ω f =150rad / s.

[0079] Step 3: Collect the grid point angle θ pcc , the enhanced hybrid synchronous control equation based on adaptive integrator is constructed, and the output frequency ω of the doubly fed wind power converter and the resynchronization angle θ of the grid-type doubly fed wind power converter are calculated. ref ;

[0080] The expression of the enhanced hybrid synchronous control equation based on the adaptive integrator is:

[0081]

[0082] In the formula, K P is the active droop coefficient, ω0 is the rated frequency, P ref is the active power reference value, K P,VBS To enhance the proportionality factor of the hybrid synchronous controller, V pcc is the effective value of the grid connection point voltage, K I,VBS is the adaptive integration coefficient of the adaptive integrator, and s is the Laplace operator.

[0083] In this embodiment, K is set P =2e5,ω0=50Hz,P ref =2e6W,K P,VBS =26, V pcc =398V Step 3 is the enhanced hybrid synchronous control link based on adaptive integrator. For specific control, see Figure 2 .

[0084] Step 4: Calculate the stator voltage amplitude U s , And as the d-axis stator voltage reference value, U ref is the voltage reference value, Q ref is the reactive power reference value, K q is the droop proportional coefficient.

[0085] In this embodiment, U is set ref =563V, Q ref =0, K q =0.075.

[0086] Step 4 is the reactive power-voltage droop control link. For specific control, see Figure 3 .

[0087] Step 5, calculate the q-axis deviation r1 and d-axis deviation r2, r1 = 0-u sq , r2=U s -u sd , and input into the PI regulator of the stator voltage outer loop for processing, and the output is the dq axis rotor current command i rdref ,i rqref ; Calculate the d-axis rotor current command i rdref and the d-axis rotor current i rd The deviation between the q-axis rotor current command i rqref and the q-axis rotor current i rq The deviation between them is input into the PI regulator of the rotor current inner loop for processing, and the output is the dq axis rotor voltage command u rd_ref ,u rq_ref .

[0088] In this embodiment, the dq axis rotor current command i rdref ,i rqref and dq axis rotor voltage command u rd_ref ,u rq_ref The calculation formulas are:

[0089]

[0090] In the formula, K pi is the proportional coefficient of the PI regulator of the rotor current inner loop, K ii K is the integral coefficient of the PI regulator of the rotor current inner loop, pu is the proportional coefficient of the PI regulator of the stator voltage outer loop, K iu are the proportional coefficient and integral coefficient of the PI regulator of the stator voltage outer loop.

[0091] In this embodiment, K is set pi =1, K ii =53, K pu =0.8, K iu =40.

[0092] Step 5 is the voltage-rotor-current double closed-loop control link. For details, see Figure 4 .

[0093] Step 6: Set the dq axis rotor voltage command u rd_ref ,u rq_ref After the inverse coordinate transformation, the three-phase modulation wave U of the bridge arm voltage of the main inverter is obtained. ma ,U mb ,U mc , and then after modulation by the PWM link, the switch control signal s in the main inverter is generated a ,s b ,s c , to achieve stable control of the doubly-fed wind power converter.

[0094] In this embodiment, the adaptive integral coefficient K of the adaptive integrator in step 3 is I,VBS is determined as follows:

[0095] Step 3.1, let the adaptive integral coefficient K I,VBS satisfy:

[0096]

[0097] Among them, K I,0 is the reference value of adaptive integration, V pcc,f is the voltage amplitude after the fault, V N is the rated value of the grid connection point voltage, K t is the adjustable gain, and the adjustable gain K t satisfy:

[0098]

[0099] In the formula, K t,0 The adjustable gain K t The benchmark value, k SCR is the short-circuit ratio of the power grid, P N is the rated active power, e is the natural constant;

[0100] The reference value K of the adaptive integral I,0 and the adjustable gain K t The reference value K t,0 To be determined parameter.

[0101] Step 3.2: Introduce the resynchronization angle θ of the grid-connected double-fed wind power converter when there is no control method ref Minimum acceleration time required for divergence The shortest acceleration time satisfy:

[0102]

[0103] In the formula, θ N is the rated active power P N The corresponding steady-state synchronization angle;

[0104] Introduce the q-axis component grid-connected point voltage u within the synchronization time Δt q The average value of the change The average satisfy:

[0105]

[0106] In the formula, t0 represents the grid voltage drop time;

[0107] Step 3.3, let P ref =P N , P = 0, the reference value K of the adaptive integral I,0 The calculation formula is:

[0108]

[0109] make P ref =P N ,P=0、V pcc,f =0, adjustable gain K t The reference value K t,0 The calculation formula is:

[0110]

[0111] The reference value K of the adaptive integral calculated in step 3.3 is I,0 and adjustable gain K t The reference value K t,0 Substituting into step 3.1, we get the adaptive integral coefficient K of the adaptive integrator: I,VBS .

[0112] In this embodiment, set t0=3s,θ N =π / 6, k SCR =2.

[0113] In the enhanced hybrid synchronous control based on adaptive integrator, the present invention takes into account the adaptability of control parameters under different grid short-circuit ratios, grid voltage drop depths and active output levels before faults, establishes clear adaptive integral parameter design principles, and realizes efficient and stable operation of grid-connected doubly-fed wind power converters.

[0114] In order to demonstrate the beneficial effects of the present invention, the control method of the present invention was simulated.

[0115] The transient stability boundary of the grid-connected doubly-fed wind power converter is as follows: Figure 5 As shown. Among them, the vertical axis is the short circuit ratio (SCR), and the horizontal axis is the grid voltage amplitude Vg . By setting the short circuit ratio in the range of 1-10 and the grid voltage in the range of 0.1-1.0pu (standard per unit value), the transient stability boundary represented by the short circuit ratio SCR and the grid voltage amplitude can be drawn in two-dimensional coordinates. The control groups are the control schemes with no strategy application and the HSC strategy. Compared with the traditional HSC strategy, the transient stability boundary of the grid-type doubly fed wind power converter is significantly increased by the proposed EHSC strategy.

[0116] In the present invention, the simulation diagram when using HSC synchronous control is as follows: Figure 6 As shown. The left ordinate is the resynchronization angle θ ref , the right vertical axis is the output frequency ω of the doubly fed wind power converter, and the horizontal axis is time t. The figure plots the resynchronization angle θ ref , the total output frequency Δω of the doubly-fed wind power converter and the q-axis grid-connected point voltage u q The change in V pcc,q The area marked with "+" in the figure is the acceleration area of ​​the total output frequency Δω of the doubly fed wind power converter during the resynchronization process. This figure shows the resynchronization angle θ of the grid-type doubly fed wind power converter when using the traditional hybrid synchronous control strategy. ref The divergence process, Δω and V pcc,q The value cannot be stably controlled near 0.

[0117] In the present invention, the simulation diagram when using EHSC synchronous control is as follows: Figure 7 As shown. The left ordinate is the resynchronization angle θ ref , the right vertical axis is the double-fed wind power converter ω, and the horizontal axis is time t. The figure plots the resynchronization angle θ ref , the total output frequency Δω of the doubly-fed wind power converter and the q-axis grid-connected point voltage u q The change in V pcc,q The area marked with "+" in the figure is the acceleration area generated by the original power synchronous output, the area marked with "-" is the deceleration area with the opposite compensation direction generated by the adaptive integrator output, and the "K I,VBS The area marked by " is the transient damping generated by the adaptive integrator output. This figure shows the resynchronization angle θ of the grid-type doubly fed wind power converter when the enhanced hybrid synchronous control method is used. ref The convergence process of Δω and V pcc,q They can all be stably controlled near 0.

Claims

1. A grid-type double-fed wind power converter enhanced hybrid synchronous control method, the topological structure of the double-fed wind power converter to which the control method is applied includes a DC power supply, a main inverter, a double-fed wind turbine generator, a line impedance and a three-phase power grid connected in series in sequence; characterized in that: The steps of the control method are as follows: Step 1: Collect the three-phase voltage u of the doubly-fed wind turbine generator stator sa ,u sb ,u sc and the three-phase current i of the stator sa ,i sb ,i sc , and the dq axis stator voltage u is obtained by coordinate transformation sd ,u sq and dq axis stator current i sd ,i sq ; Collect the three-phase current i of the doubly-fed wind turbine generator rotor ra ,i rb ,i rc and the rotor electrical angular velocity θ r , and the dq-axis rotor current i is obtained by coordinate transformation rd ,i rq ; Step 2: First, according to the dq axis stator voltage u sd ,u sq and dq axis stator current i sd ,i sq , calculate the stator output active power p and stator output reactive power q of the doubly-fed wind turbine generator, and then perform low-pass filtering to calculate the active power P after the low-pass filter and the reactive power Q after the low-pass filter; Step 3: Collect the grid point angle θ pcc , the enhanced hybrid synchronous control equation based on adaptive integrator is constructed, and the output frequency ω of the doubly fed wind power converter and the resynchronization angle θ of the grid-type doubly fed wind power converter are calculated. ref ; The expression of the enhanced hybrid synchronous control equation based on the adaptive integrator is: In the formula, K P is the active droop coefficient, ω0 is the rated frequency, P ref is the active power reference value, K P,VBS To enhance the proportionality factor of the hybrid synchronous controller, V pcc is the effective value of the grid connection point voltage, K I,VBS is the adaptive integration coefficient of the adaptive integrator, s is the Laplace operator; Step 4: Calculate the stator voltage amplitude U s , And as the d-axis stator voltage reference value, U ref is the voltage reference value, Q ref is the reactive power reference value, K q is the droop proportional coefficient; Step 5, calculate the q-axis deviation r1 and d-axis deviation r2, r1 = 0-u sq , r2=U s -u sd , and input into the PI regulator of the stator voltage outer loop for processing, and the output is the dq axis rotor current command i rdref ,i rqref ; Calculate the d-axis rotor current command i rdref and the d-axis rotor current i rd The deviation between the q-axis rotor current command i rqref and the q-axis rotor current i rq The deviation between them is input into the PI regulator of the rotor current inner loop for processing, and the output is the dq axis rotor voltage command u rd_ref ,u rq_ref ; Step 6: Set the dq axis rotor voltage command u rd_ref ,u rq_ref After the inverse coordinate transformation, the three-phase modulation wave U of the bridge arm voltage of the main inverter is obtained. ma ,U mb ,U mc , and then after modulation by the PWM link, the switch control signal s in the main inverter is generated a ,s b ,s c , to achieve stable control of the doubly-fed wind power converter.

2. The method for enhancing hybrid synchronous control of a grid-connected doubly-fed wind power converter according to claim 1, characterized in that: The calculation formulas for the stator output active power p and stator output reactive power q of the doubly-fed wind turbine generator in step 2 are: The calculation formula of the active power P after the low-pass filter and the reactive power Q after the low-pass filter is: In the formula, ω f is the cutoff frequency of the low-pass filter.

3. The method for enhanced hybrid synchronous control of a grid-connected doubly-fed wind power converter according to claim 1, characterized in that: The adaptive integral coefficient K of the adaptive integrator in step 3 is I,VBS is determined as follows: Step 3.1, let the adaptive integral coefficient K I,VBS satisfy: Among them, K I,0 is the reference value of adaptive integration, V pcc,f is the voltage amplitude after the fault, V N is the rated value of the grid connection point voltage, K t is the adjustable gain, and the adjustable gain K t satisfy: In the formula, K t,0 The adjustable gain K t The benchmark value, k SCR is the short-circuit ratio of the power grid, P N is the rated active power, e is the natural constant; The reference value K of the adaptive integral I,0 and the adjustable gain K t The reference value K t,0 is a parameter to be determined; Step 3.2: Introduce the resynchronization angle θ of the grid-connected double-fed wind power converter when there is no control method ref Minimum acceleration time required for divergence The shortest acceleration time satisfy: In the formula, θ N is the rated active power P N The corresponding steady-state synchronization angle; Introduce the q-axis component grid-connected point voltage u within the synchronization time Δt q The average value of the change The average satisfy: In the formula, t0 represents the grid voltage drop time; Step 3.3, let P ref =P N , P = 0, the reference value K of the adaptive integral I,0 The calculation formula is: make P ref =P N ,P=0、V pcc,f =0, adjustable gain K t The reference value K t,0 The calculation formula is: The reference value K of the adaptive integral calculated in step 3.3 is I,0 and adjustable gain K t The reference value K t,0 Substituting into step 3.1, we get the adaptive integral coefficient K of the adaptive integrator: I,VBS .

4. The method for enhancing hybrid synchronous control of a grid-connected doubly-fed wind power converter according to claim 1, characterized in that: Step 5: The dq axis rotor current command i rdref ,i rqref and dq axis rotor voltage command u rd_ref ,u rq_ref The calculation formulas are: In the formula, K pi is the proportional coefficient of the PI regulator of the rotor current inner loop, K ii K is the integral coefficient of the PI regulator of the rotor current inner loop, pu is the proportional coefficient of the PI regulator of the stator voltage outer loop, K iu are the proportional coefficient and integral coefficient of the PI regulator of the stator voltage outer loop.

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