A network-structured doubly-fed wind power converter enhanced hybrid synchronization control method

Abstract

This invention discloses an enhanced hybrid synchronization control method for grid-type doubly-fed induction generator (DFIG) wind turbine converters, belonging to the field of electrical engineering. The control method includes enhanced hybrid synchronization control based on an adaptive integrator, reactive power-voltage droop control, and dual closed-loop control of stator voltage and rotor current. Traditional hybrid synchronization control algorithms for grid-type converters, which rely on virtual impedance, cannot solve the resynchronization stability problem of grid-type DFIG wind turbine converters when facing fault scenarios such as grid voltage dips. Furthermore, existing parameter design methods are no longer applicable to grid-type DFIG wind turbine converter systems. This invention introduces a voltage synchronization loop based on an adaptive integrator, effectively ensuring the existence of a stable operating point during faults. The established adaptive integrator parameter design principles can guarantee the adaptive adjustment capability of the DFIG wind turbine converter for synchronous stability under different fault conditions.

Description

Technical Field

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

[0002] As my country's energy structure continues to optimize and the proportion of new energy sources gradually increases, the penetration rate of doubly-fed induction generator (DFIG) wind power is constantly rising. As a crucial component connecting the DFIG wind turbine to the power grid, the converter's control structure is vital to the system's stable operation. Unlike the passive following of grid-fed control, grid-connected control exhibits better characteristics in terms of synchronization stability.

[0003] Hybrid synchronous control (HSC), as a type of synchronous control method for grid-connected converters, was initially proposed to improve the operational stability of grid-connected converter control systems under different short-circuit ratio grids. In the paper "Lima LAM, Watanabe EH. Hybrid Control Scheme for VSC Presenting Both Grid-Forming and Grid-Following Capabilities" published in IEEE Transactions on Power Delivery in 2022, the designed synchronization loop is a weighted fusion of power synchronization and voltage synchronization. Furthermore, a feedforward channel for active power control is introduced between the voltage controller and the current controller in the inner voltage loop. This allows the grid-connected converter control system, which originally had a single voltage source characteristic, to exhibit adjustable port output characteristics that combine voltage source and current source characteristics. This method of achieving a mixture of voltage source and current source characteristics is called hybrid synchronous control of the converter.

[0004] Under the basic idea of ​​hybrid synchronous control, scholars at home and abroad have proposed a series of control structures with similar functions. For example, the paper "Han F, Zhang X, Li M, et al. Stability Control for Grid-Connected Inverters Based on Hybrid-Mode of Grid-Following and Grid-Forming" published in IEEE Transactions on Power Electronics in 2023 describes how, by constructing two parallel and independent control subsystems in a single converter system and performing modulation weighting in the converter wave generation stage, the characteristics of voltage source and current source are also integrated.

[0005] The above research on hybrid synchronous control focuses on the stability problem under small disturbances, specifically addressing the control stability issues of grid-connected converter systems caused by significant fluctuations in grid impedance under the background of high-proportion renewable energy generation. Studies show that the integration of power synchronization and voltage synchronization in hybrid synchronous control not only improves the robust operation of grid-connected converter systems under short-circuit ratio variations, but its hybrid voltage synchronization element can also be equivalent to the damping winding of a synchronous generator, providing limitation on power angle motion under grid voltage faults.

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

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

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

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

[0010] Chinese patent document CN115579966A, published on January 6, 2023, entitled "A Control Method for Grid-Based Doubly Fed Wind Turbines Based on Hybrid Synchronization," designs a grid-based control scheme with DC voltage synchronization for the grid-side converter of a doubly fed wind turbine, achieving autonomous grid-based operation of the doubly fed wind turbine. Both the rotor-side converter and the grid-side converter simultaneously participate in actively supporting the voltage / frequency of the power grid, and synchronization is not dependent on a phase-locked loop during operation, improving its stability under weak grid conditions. Its shortcomings include:

[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 most active power output has not been studied and analyzed.

[0012] (2) This method focuses on the synchronization stability analysis of doubly fed wind turbines under small signals, and does not involve the study of synchronization stability under large disturbance transients.

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

[0014] In summary, the existing technology has the following problems:

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

[0016] (2) In the existing hybrid synchronous control method for grid-connected converters, the virtual impedance algorithm is used to ensure a stable and continuous deviation between the voltage angle and the synchronization angle at the grid connection point, thereby achieving stable and continuous correction of active power command and system damping. However, the virtual impedance link increases the equivalent output impedance of the system, causing the voltage source characteristics at the grid connection point to shift, and reducing the active power output limit of the system in the control sense. This is not conducive to ensuring the existence of a stable operating point during faults.

[0017] (3) The hybrid synchronous control method was initially proposed to optimize the damping characteristics of grid-type converters based on second-order active power controllers, and could improve the power angle overshoot phenomenon caused by improper configuration of virtual inertia and virtual damping. However, for grid-type doubly-fed wind power converter systems using first-order active power controllers (droop control), the hybrid control method loses its original damping optimization objective. Therefore, existing parameter design methods are no longer applicable to grid-type doubly-fed wind power converter systems. Summary of the Invention

[0018] The technical problem to be solved by this invention is to address the shortcomings of the existing technology. It proposes an enhanced hybrid synchronous control method for grid-type doubly-fed wind power converters. This enhanced hybrid synchronous control method (EHSC) incorporates a voltage synchronization loop based on an adaptive integrator and establishes an adaptive integrator parameter design principle to ensure the adaptive adjustment capability of the doubly-fed wind power converter for synchronous stability under different fault conditions.

[0019] To achieve the above-mentioned objectives, this invention provides an enhanced hybrid synchronous control method for a grid-type doubly-fed wind power converter. The topology of 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. The steps of the control method are as follows:

[0020] Step 1: Collect the three-phase voltage u of the doubly-fed wind turbine 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 through 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 rotor. ra i rb i rc With rotor electric angular velocity θ r And the rotor current i on the dq axis is obtained through coordinate transformation. rd i rq ;

[0021] Step 2, firstly, based on 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 are calculated, and then a low-pass filter is applied to calculate the active power P and reactive power Q after the low-pass filter.

[0022] Step 3, collect the grid connection point angle θ pcc An enhanced hybrid synchronization control equation based on an adaptive integrator was constructed, and the output frequency ω of the doubly-fed wind turbine converter and the resynchronization angle θ of the grid-type doubly-fed wind turbine converter were calculated. ref ;

[0023] The expression for the enhanced hybrid synchronization control equation based on the adaptive integrator is as follows:

[0024]

[0025] In the formula, K P P is the active droop factor, ω0 is the rated frequency, and P is the active droop factor. ref It is an active power reference value, K P,VBS To enhance the proportional gain of the hybrid synchronous controller, V pcc K represents the effective value of the grid connection point voltage.I,VBS represents the adaptive integration coefficients of the adaptive integrator, and s is the Laplace operator;

[0026] Step 4: Calculate the stator voltage amplitude U. s , And used as a reference value for the d-axis stator voltage, U ref Q is the voltage reference value. ref K is the reference value for reactive power. q This is the drooping ratio coefficient;

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

[0028] Step 6, transfer the dq axis rotor voltage command u rd_ref ,u rq_ref The three-phase modulation wave U of the main inverter bridge arm voltage is obtained after inverse coordinate transformation. ma U mb U mc After modulation by the PWM stage, the switching control signal s in the main inverter is generated. a ,s b ,s c This enables stable control of the doubly fed wind power converter.

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

[0030]

[0031] The formulas for calculating the active power P and reactive power Q after passing through the low-pass filter are as follows:

[0032]

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

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

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

[0036]

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

[0038]

[0039] In the formula, K t,0 For adjustable gain K t The baseline value, k SCR P represents the short-circuit ratio of the power grid. N Where e is the rated active power, and e is the natural constant.

[0040] The baseline value K of the adaptive integral I,0 and the adjustable gain K t The benchmark value K t,0 These are parameters to be determined.

[0041] Step 3.2, introduce the resynchronization angle θ of the grid-type doubly-fed wind power converter when no control method is applied. ref Shortest acceleration time required for divergence The shortest acceleration time satisfy:

[0042]

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

[0044] Introducing the q-axis component of the grid connection point voltage u within the synchronization time Δt q average of changes The average satisfy:

[0045]

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

[0047] Step 3.3, let P ref =P N P = 0, the baseline value K for adaptive integration I,0 The formula for calculation is:

[0048]

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

[0050]

[0051] The baseline value K of the adaptive integral calculated in step 3.3 is used. I,0 and adjustable gain K t The benchmark value K t,0 Substituting into step 3.1, we obtain the adaptive integration coefficients K of the adaptive integrator. I,VBS .

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

[0053]

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

[0055] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0056] 1. Addressing the differences in resynchronization control between grid-connected converters and grid-connected doubly-fed induction generator (DFIG) wind turbine converters, this invention employs an enhanced hybrid synchronization control method based on an adaptive integrator. This method solves the transient damping problem required during resynchronization, providing a new convergent operating point when the original system lacks a stable operating point, effectively suppressing the divergence of system synchronization angle and power angle during faults. This improves the stability of the grid-connected DFIG wind turbine converter during resynchronization.

[0057] 2. The enhanced hybrid synchronous control method proposed in this invention can continuously correct active power commands and system damping stability without relying on virtual impedance algorithms. This effectively reduces the equivalent output impedance of the system, ensures the voltage source characteristics of the grid-connected doubly-fed wind power converter at the grid connection point, improves the active power output limit of the system in a control sense, and helps ensure the existence of a stable operating point during faults.

[0058] 3. This invention fully considers the adaptability of control parameters under different grid short-circuit ratios, grid voltage drop depths, and active power output levels before faults, overcomes the problem of unclear traditional control parameter design, establishes a clear adaptive integral parameter design principle, and realizes the efficient and stable operation of grid-type doubly fed wind power converters. Attached Figure Description

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

[0060] Figure 2 This is a diagram of the enhanced hybrid synchronization control structure based on an adaptive integrator in this invention.

[0061] Figure 3 This is a diagram of the reactive power-voltage droop control structure in this invention;

[0062] Figure 4 This is a diagram of the stator voltage and rotor current dual closed-loop control structure in this invention;

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

[0064] Figure 6 This is a simulation diagram of HSC synchronous control used in this invention;

[0065] Figure 7 This is a simulation diagram of the use of EHSC synchronous control in this invention; Detailed Implementation

[0066] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0067] Figure 1 This is the overall control diagram of the method of the present invention. (From...) Figure 1 As can be seen, the present invention provides an enhanced hybrid synchronous control method for a grid-type doubly-fed wind power converter. The topology of 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.

[0068] exist Figure 1 Above, DFIG is a doubly fed wind turbine, U dcL is the voltage value at the DC power supply. g R is the inductance value in the line impedance. g This represents the resistance value in the line impedance. In this embodiment of the invention, R is taken as... g =0.65mH, L g =0.01Ω.

[0069] In this embodiment, the doubly-fed wind turbine is a wound-rotor induction motor with the following rated parameters: rated speed 1200 r / min, stator rated voltage 380V, rotor rated voltage 1070V, stator rated current 13.9A, rotor rated current 6.8A, 3 pole pairs, and 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 As can be seen, the control method of the present invention includes the following steps:

[0071] Step 1: Collect the three-phase voltage u of the doubly-fed wind turbine 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 through 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 rotor. ra i rb i rc With rotor electric angular velocity θ r And the rotor current i on the dq axis is obtained through coordinate transformation. rd i rq .

[0072] Step 2, firstly, based on 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 are calculated, and then a low-pass filter is applied to calculate the active power P and reactive power Q after the low-pass filter.

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

[0074]

[0075] The formulas for calculating the active power P and reactive power Q after passing through the low-pass filter are as follows:

[0076]

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

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

[0079] Step 3, collect the grid connection point angle θ pcc An enhanced hybrid synchronization control equation based on an adaptive integrator was constructed, and the output frequency ω of the doubly-fed wind turbine converter and the resynchronization angle θ of the grid-type doubly-fed wind turbine converter were calculated. ref ;

[0080] The expression for the enhanced hybrid synchronization control equation based on the adaptive integrator is as follows:

[0081]

[0082] In the formula, K P P is the active droop factor, ω0 is the rated frequency, and P is the active droop factor. ref It is an active power reference value, K P,VBS To enhance the proportional gain of the hybrid synchronous controller, V pcc K represents the effective value of the grid connection point voltage. I,VBS denoted as the adaptive integration coefficients of the adaptive integrator, and s as 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 an enhanced hybrid synchronization control loop based on an adaptive integrator. See details for specific control procedures. Figure 2 .

[0084] Step 4: Calculate the stator voltage amplitude U. s , And used as a reference value for the d-axis stator voltage, U ref Q is the voltage reference value. ref K is the reference value for reactive power. q This is the drooping ratio 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 stage; see details below. Figure 3 .

[0087] Step 5, calculate the q-axis deviation r1 and the d-axis deviation r2, r1 = 0 - u sq r2 = U s -u sd The input is then processed by the PI regulator in the outer loop of the stator voltage, and the output is the dq-axis rotor current command i. rdref i rqref ; Calculate the d-axis rotor current command i rdref With d-axis rotor current i rd Deviation between, q-axis rotor current command i rqref With q-axis rotor current i rq The deviation between them is input into the PI regulator of the inner loop of the rotor current 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 as follows:

[0089]

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

[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 and rotor current dual closed-loop control loop; see details below. Figure 4 .

[0093] Step 6, transfer the dq axis rotor voltage command u rd_ref ,u rq_ref The three-phase modulation wave U of the main inverter bridge arm voltage is obtained after inverse coordinate transformation. ma U mb U mc After modulation by the PWM stage, the switching control signal s in the main inverter is generated. a ,s b ,s c This enables stable control of the doubly fed wind power converter.

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

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

[0096]

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

[0098]

[0099] In the formula, K t,0 For adjustable gain K t The baseline value, k SCR P represents the short-circuit ratio of the power grid. N Where e is the rated active power, and e is the natural constant.

[0100] The baseline value K of the adaptive integral I,0 and the adjustable gain K t The benchmark value K t,0 These are parameters to be determined.

[0101] Step 3.2, introduce the resynchronization angle θ of the grid-type doubly-fed wind power converter when no control method is applied. ref Shortest acceleration time required for divergence The shortest acceleration time satisfy:

[0102]

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

[0104] Introducing the q-axis component of the grid connection point voltage u within the synchronization time Δt q average of changes The average satisfy:

[0105]

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

[0107] Step 3.3, let P ref =P N P = 0, the baseline value K for adaptive integration I,0 The formula for calculation is:

[0108]

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

[0110]

[0111] The baseline value K of the adaptive integral calculated in step 3.3 is used. I,0 and adjustable gain K t The benchmark value K t,0 Substituting into step 3.1, we obtain the adaptive integration coefficients K of the adaptive integrator. I,VBS .

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

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

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

[0115] The transient stability boundary of a grid-type doubly fed wind power converter is as follows: Figure 5 As shown in the figure. The vertical axis represents the short-circuit ratio (SCR), and the horizontal axis represents the grid voltage amplitude V.g By setting the short-circuit ratio to 1-10 and the grid voltage to 0.1-1.0 pu (per unit value) at equal scales, the transient stability boundary can be plotted using a two-dimensional coordinate system with the short-circuit ratio (SCR) and grid voltage amplitude. The control groups are the control schemes without a strategy and those using the HSC strategy, respectively. Compared to the traditional HSC strategy, the proposed EHSC strategy significantly increases the transient stability boundary of the grid-connected doubly-fed wind turbine converter.

[0116] In this invention example, the simulation diagram when using HSC synchronous control is as follows: Figure 6 As shown. The left vertical axis represents the resynchronization angle θ. ref The right vertical axis represents the output frequency ω of the doubly-fed wind turbine converter, and the horizontal axis represents time t. The resynchronization angle θ is also plotted in the figure. ref The total output frequency Δω and q-axis grid-connected voltage u of the doubly fed wind power converter q Change V pcc,q The figure shows the change process, with the "+" area representing the acceleration region caused by the total output frequency Δω of the doubly-fed wind turbine converter during resynchronization. This figure illustrates the resynchronization angle θ of a grid-type doubly-fed wind turbine converter when using a traditional hybrid synchronization control strategy. ref The divergence process, Δω and V pcc,q None of them can be stably controlled near 0.

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

Claims

1. A method for enhancing hybrid synchronous control of a grid-type doubly-fed wind power converter, wherein the topology of 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; characterized in that, The control method comprises the following steps: Step 1: Collect the three-phase voltage u of the doubly-fed wind turbine 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 through 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 rotor. ra i rb i rc With rotor electric angular velocity θ r And the rotor current i on the dq axis is obtained through coordinate transformation. rd i rq ; Step 2, firstly, based on 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 are calculated, and then a low-pass filter is applied to calculate the active power P and reactive power Q after the low-pass filter. Step 3, collect the grid connection point angle θ pcc An enhanced hybrid synchronization control equation based on an adaptive integrator was constructed, and the output frequency ω of the doubly-fed wind turbine converter and the resynchronization angle θ of the grid-type doubly-fed wind turbine converter were calculated. ref ; The expression for the enhanced hybrid synchronization control equation based on the adaptive integrator is as follows: In the formula, K P P is the active droop factor, ω0 is the rated frequency, and P is the active droop factor. ref It is an active power reference value, K P,VBS To enhance the proportional gain of the hybrid synchronous controller, V pcc K represents the effective value of the grid connection point voltage. I,VBS represents the adaptive integration coefficients of the adaptive integrator, and s is the Laplace operator; Step 4: Calculate the stator voltage amplitude U. s , And used as a reference value for the d-axis stator voltage, U ref Q is the voltage reference value. ref K is the reference value for reactive power. q This is the drooping ratio coefficient; Step 5, calculate the q-axis deviation r1 and the d-axis deviation r2, r1 = 0 - u sq r2 = U s -u sd The input is then processed by the PI regulator in the outer loop of the stator voltage, and the output is the dq-axis rotor current command i. rdref i rqref ; Command i for calculating d-axis rotor current rdref With d-axis rotor current i rd Deviation between, q-axis rotor current command i rqref With q-axis rotor current i rq The deviation between them is input into the PI regulator of the inner loop of the rotor current for processing, and the output is the dq axis rotor voltage command u. rd_ref ,u rq_ref ; Step 6, transfer the dq axis rotor voltage command u rd_ref ,u rq_ref The three-phase modulation wave U of the main inverter bridge arm voltage is obtained after inverse coordinate transformation. ma U mb U mc After modulation by the PWM stage, the switching control signal s in the main inverter is generated. a ,s b ,s c This enables stable control of the doubly fed wind power converter.

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

3. The method for enhancing hybrid synchronous control of a grid-type doubly-fed wind power converter according to claim 1, characterized in that, The adaptive integration coefficient K of the adaptive integrator described in step 3 I,VBS The determination is as follows: Step 3.1, let the adaptive integral coefficient K I,VBS satisfy: Among them, K I,0 V is the baseline value for adaptive integration. pcc,f V represents the voltage amplitude after the fault. N K is the rated value of the grid connection point voltage. t Let the adjustable gain be K. t satisfy: In the formula, K t,0 For adjustable gain K t The baseline value, k SCR P represents the short-circuit ratio of the power grid. N Where e is the rated active power, and e is the natural constant. The baseline value K of the adaptive integral I,0 and the adjustable gain K t The benchmark value K t,0 These are parameters to be determined. Step 3.2, introduce the resynchronization angle θ of the grid-type doubly-fed wind power converter when no control method is applied. ref Shortest acceleration time required for divergence The shortest acceleration time satisfy: In the formula, θ N Rated active power P N The corresponding steady-state synchronization angle; Introducing the q-axis component of the grid connection point voltage u within the synchronization time Δt q average of changes The average satisfy: In the formula, t0 represents the voltage drop time of the power grid; Step 3.3, let P ref =P N P = 0, the baseline value K for adaptive integration I,0 The formula for calculation is: make P ref =P N P = 0, V pcc,f =0, adjustable gain K t The benchmark value K t,0 The formula for calculation is: The baseline value K of the adaptive integral calculated in step 3.3 is used. I,0 and adjustable gain K t The benchmark value K t,0 Substituting into step 3.1, we obtain the adaptive integration coefficients K of the adaptive integrator. I,VBS .

4. The method for enhancing hybrid synchronous control of a grid-type doubly-fed wind power converter according to claim 1, characterized in that, Step 5 describes 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 as follows: In the formula, K pi K is the proportional coefficient of the PI regulator in the inner loop of the rotor current. ii K is the integral coefficient of the PI regulator in the inner loop of the rotor current. pu K is the proportional coefficient of the PI regulator in the outer loop of the stator voltage. iu These are the proportional and integral coefficients of the PI regulator in the outer loop of the stator voltage.

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