Active frequency and voltage support control method for hybrid wind farm based on grid grouping and switching

Abstract

The present invention discloses a method for active frequency and voltage support control of a hybrid wind farm based on grid grouping and switching, which belongs to the field of power system control, including: constructing a clustered distributed active frequency and voltage control strategy for a hybrid wind farm to actively support the power grid with frequency and voltage; adaptively adjusting active support control parameters and coupling compensation coefficients in the clustered distributed active frequency and voltage control strategy according to the wind turbine operating state and the hybrid wind farm grid connection strength changes; using the coupling compensation coefficient, performing power feedforward compensation on the wind turbine active reference value and wind turbine reactive reference value in the adaptively adjusted clustered distributed active frequency and voltage control strategy to form a final clustered distributed active frequency and voltage control strategy; using the final clustered distributed active frequency and voltage control strategy to actively support the frequency and voltage of the hybrid wind farm. The frequency-voltage support capability of the hybrid wind farm is improved under the premise of stable grid connection.

Description

Technical Field

[0001] The present invention belongs to the field of power system control, and more specifically, relates to a hybrid wind farm frequency and voltage active support control method based on grid grouping and switching. Background Art

[0002] With the rapid development of new energy power generation technology, the proportion of new energy power electronic power sources in my country's power installed capacity has continued to rise. Wind energy, as one of the most important renewable energy power generation methods, has attracted widespread attention from all over the world. At present, wind turbines widely used in actual wind farms are all controlled by grid-following control. In recent years, many scholars have proposed grid-following control converters as voltage source control, which are expected to form a grid-following control-grid-following control hybrid wind farm together with wind turbines controlled by grid-following control. The grid-following control-grid-following control hybrid wind farm can combine the voltage source control advantages of grid-following control and the current source control advantages of grid-following control. It has strong stability and good operation flexibility, and has broader application prospects in the future. Therefore, how to maintain the stable operation of wind and solar power generation systems under the conditions of random fluctuations in wind and solar resources, changes in the intensity of access to the power grid, and various disturbances, and further explore its flexibility, is the core bottleneck that restricts new energy from becoming the main power source.

[0003] The stability issues of new energy units connected to the power grid mainly focus on voltage and frequency issues. The frequency is coupled with the active power output of the system, and the voltage support is coupled with the reactive power of the system. Therefore, in the analysis of new energy units, it is necessary to focus on analyzing the constraints of active and reactive power, realize active and reactive power decoupling control, and solve the equivalence of the external characteristics of synchronous generators from the single-machine level. This allows the wind and solar power generation units to support the restoration of voltage under fault conditions and solve the relationship between reactive power and the support voltage of the system. Active power regulation and frequency fluctuation suppression can be achieved when the frequency of the system fluctuates.

[0004] Wind turbines participate in frequency support mainly through load reduction control and rotor kinetic energy control. The former will cause wind abandonment and poor economic efficiency. The latter participates in system frequency support by releasing the rotor kinetic energy stored in the wind turbine, which can be regarded as a more ideal support solution. Wind turbines participate in voltage support mainly through reactive power control and voltage control. The former supports the voltage by changing the reactive reference by detecting voltage changes. The latter changes according to the setting of the voltage outer loop to achieve grid-connected voltage following. With the formation of a hybrid wind farm with grid-following control and grid-building control, it is necessary to further study the coordinated control strategy of wind farm frequency and voltage support. Make full use of the active and reactive regulation resources within the wind farm. Combine the actual operating status and regulation potential of each unit. Further improve the frequency stability and voltage stability of the system.

[0005] In summary, the adaptability of the hybrid wind farm to the stability of the grid-connected strong and weak grid is of universal and critical significance to the reliable operation and absorption of large-scale new energy access. It is urgent to further explore the voltage source support capability of the hybrid wind farm and fully combine it with its current source support capability to realize the switching of the voltage source and current source control mode based on the real-time change of the short-circuit ratio of the power grid. Summary of the invention

[0006] In view of the defects of the prior art and the need for improvement, the present invention provides a method for active frequency and voltage support control of a hybrid wind farm based on grouping and switching of a follow-up / grid-connected wind farm, which aims to fully tap the voltage source and current source control capabilities of the follow-up / grid-connected hybrid wind farm, and to achieve support by outputting active power and reactive power to the maximum extent possible while ensuring system stability.

[0007] To achieve the above-mentioned purpose, according to one aspect of the present invention, a method for active frequency and voltage support control of a hybrid wind farm based on grouping and switching of a grid-forming wind farm is provided, comprising: constructing a grouped distributed active frequency and voltage control strategy for a hybrid wind farm to perform active frequency and voltage support on a power grid, wherein, in a hybrid wind farm, a group of grid-forming wind turbines adopts a leader-follower wind turbine active response mode for frequency support, and a group of grid-forming wind turbines adopts a multi-stage active voltage support mode; according to the wind turbine operating state and the change in the grid-connected strength of the hybrid wind farm, the active support output of the hybrid wind farm under the grouped distributed active frequency and voltage control strategy does not exceed its maximum support capacity, and the frequency regulation is decoupled from the voltage regulation as the regulation principle, the active support control parameters and coupling compensation coefficients in the grouped distributed active frequency and voltage control strategy are adaptively adjusted; using the coupling compensation coefficient, power feedforward compensation is performed on the active reference value of the wind turbine and the reactive reference value of the wind turbine in the grouped distributed active frequency and voltage control strategy after adaptive adjustment, to form a final grouped distributed active frequency and voltage control strategy; using the final grouped distributed active frequency and voltage control strategy, the frequency and voltage active support control of the hybrid wind farm is performed.

[0008] Furthermore, in the constructed clustered distributed active frequency and voltage control strategy, the control process of the grid-following wind turbine is:

[0009]

[0010] The control method of the leading fan and the non-leading fan in the grid-following fan group is:

[0011]

[0012]

[0013] Among them, θ PLLis the output phase angle of the phase-locked loop synchronization loop of the grid-type wind turbine, t is the time, ω is the synchronous frequency of the wind turbine, k pPLL k is the proportional coefficient of the grid-type fan phase-locked loop control, iPLL is the integral coefficient of the grid-type fan phase-locked loop control, u pccq is the q-axis voltage component of the grid-connected wind turbine, i dref_VSC is the d-axis reference value of the inner loop current control of the grid-type fan, i qref_VSC is the q-axis reference value of the inner loop current control of the grid-type fan, k p1 is the first proportionality coefficient, k p2 is the second proportionality coefficient, k i1 is the first integral coefficient, k i2 is the second integral coefficient, P ref is the active reference value of the inverter, P is the actual active value of the inverter, Q ref is the reactive power reference value of the inverter, Q is the actual reactive power value of the inverter, P ref_leader , P ref_i are the active power reference values ​​output by the dominant wind turbine and the i-th non-dominant wind turbine, respectively. MPPT K is the active power of the input grid-type wind turbine maximum power tracking, dr , K in They represent the droop coefficient and integral coefficient of the virtual inertia comprehensive control of the fan, s is the control variable of the controller in the complex frequency domain, f0 is the initial reference value of the frequency of the grid-following fan, f is the actual operating value of the frequency of the grid-following fan, k PPi , k IPi They represent the proportional parameter and integral parameter of consistency control respectively, and x j 、x i are the consistency factors of fans j and i respectively.

[0014] Furthermore, in the constructed clustered distributed active frequency and voltage control strategy, the control process of the grid-type wind turbine is:

[0015]

[0016] The control method of each grid-type fan in the grid-type fan group is:

[0017]

[0018] Among them, E c , δ c ,ω c are the potential amplitude, power angle, and angular frequency of the grid-type wind turbine, t is time, ω0 is the synchronous fundamental frequency angular frequency, P cref , P c , Q cref , Q sThey are respectively the active reference value, active actual value, reactive reference value and reactive actual value outputted by the grid-connected wind turbine to the grid connection point, D δ is the damping coefficient, K q , K u are the reactive power coefficient and voltage coefficient of the reactive power voltage control loop, U ref , U s are the grid-connected point voltage reference value and voltage amplitude respectively, J is the inertia coefficient of the virtual synchronous control loop of the grid-connected wind turbine, and J i is the inertia coefficient of the i-th grid-type fan, ω i is the output speed of the i-th grid-type fan, P o_i is the output active power of the i-th grid-type wind turbine, D i is the damping coefficient of the i-th grid-type fan, P GFMi , Q GFMi are respectively the active power reference value and reactive power reference value of the i-th grid-type wind turbine consistency control, N i is the number of grid-type wind turbines in the station, a ij is the active consistency coefficient between the i-th grid-type wind turbine and the j-th grid-type wind turbine, P i , P j are the active power output values ​​of the i-th and j-th grid-type wind turbines, respectively, and b ij is the reactive power consistency coefficient between the i-th grid-type wind turbine and the j-th grid-type wind turbine, Q i , Q j are the reactive power values ​​output by the i-th and j-th grid-type wind turbines, Q o_i is the output reactive power of the i-th grid-type wind turbine.

[0019] Furthermore, in the clustered distributed active frequency and voltage control strategy, the adaptive adjustment amount of the grid-following wind turbine is:

[0020] ΔP w,i (t) = k wdr,i ×Δf+k win,i ×df / dt

[0021] =[k fdr0 +k adr0 ×(1-x i )]×Δf+[k fin0 +k ain0 ×(1-x i )]×df / dt

[0022] The adaptive adjustment amount of the grid-type fan is:

[0023] ΔQ ref_GFM =K qu (1-Upcc )

[0024] Among them, ΔP w,i (t) is the compensation power in the adaptive control process of the grid-following fan, k wdr,i is the droop coefficient, Δf is the frequency change between the actual frequency and the initial frequency, k win,i is the inertia coefficient, f is the actual operating value of the frequency of the grid-type fan, k fdr0 , k adr0 are the droop fixed coefficient reference value and adaptive coefficient reference value corresponding to the preset wind farm state, x i is the consistency factor of fan i, k fin0 , k ain0 They are the fixed part coefficient and adaptive part coefficient of the inertia coefficient of the wind farm, ΔQ ref_GFM is the reactive power output value of the grid-type wind turbine, K qu is the reactive voltage support factor, U pcc is the grid-connected voltage of the system.

[0025] Furthermore, the coupling compensation coefficient is:

[0026]

[0027] Among them, K c is the coupling compensation coefficient, K cmax is the maximum value of the coupling compensation coefficient, SCR max is the maximum short-circuit ratio of the wind farm, SCR is the grid-connected short-circuit ratio, K c Adaptive adjustment as SCR changes.

[0028] Furthermore, the compensation method of power feedforward compensation is:

[0029]

[0030] Among them, P ref_GFL is the active reference value of the grid-type fan, Q ref_GFL P is the reactive power reference value of the grid-following wind turbine, ref_GFM is the active reference value of the grid-type wind turbine, Q ref_GFM is the reactive power reference value of the grid-type wind turbine, P MPPT is the active power of the input grid-type wind turbine maximum power tracking, P sup is the active power increment of the grid-following wind turbine in the active support stage, ΔQ ad is the reactive coupling caused by the increase of active power in the active support process, G QP_GFL (s) is the reactive-active coupling transfer function of the grid-connected wind turbine, Q0 is the initial value of reactive power, K cis the coupling compensation coefficient, ΔP ad is the active power support change value, G PQ_GFL (s) is the active-reactive coupling transfer function of the grid-following wind turbine, P0 is the active reference value of the virtual synchronous control loop of the grid-building wind turbine, G QP_GFM (s) is the reactive-active coupling transfer function of the grid-type wind turbine, G PQ_GFM (s) is the active-reactive coupling transfer function of the grid-type wind turbine.

[0031] Furthermore, in the frequency and voltage active support control stage of the hybrid wind farm, if the grid-type wind turbine group reaches the maximum current inner loop constraint, the method further includes: switching the grid-type wind turbine control to the grid-following wind turbine control, and the switching method is:

[0032]

[0033] Among them, ω is the synchronous frequency of the fan, ω0 is the synchronous fundamental frequency angular frequency, Δω syn is the compensation value of DC synchronous loop control, K ω is the speed coefficient of the pre-synchronization process, s is the control variable of the controller in the complex frequency domain, θ GFL is the output phase angle of the grid-following control, θ GFM is the output phase angle of the grid-type control, E is the actual value of the output voltage of the fan, E0 is the initial value of the output voltage of the fan, ΔE syn is the compensation amount of internal potential, K E is the electromotive force adjustment coefficient, U is the grid voltage value, i dref is the d-axis current operating reference value of the inner loop current control of the wind turbine grid-side controller, i dref_GFM is the reference value of the d-axis current of the current inner loop of the grid-type wind turbine, Δi is the compensation value of the current loop, K ii is the current compensation coefficient, i dref_GFL It is the current inner loop reference value of the grid-following fan.

[0034] Furthermore, after switching, when the grid-type wind turbine group is within the maximum current inner loop constraint, the method further includes: switching back to the grid-type wind turbine control to control the grid-type wind turbine group.

[0035] According to another aspect of the present invention, a hybrid wind farm frequency and voltage active support controller based on grouping and switching of the follow-up network is provided, comprising: a processor; a memory storing a computer executable program, which, when executed by the processor, enables the processor to execute the hybrid wind farm frequency and voltage active support control method based on grouping and switching of the follow-up network as described above.

[0036] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

[0037] (1) A frequency and voltage active support control method for a hybrid wind farm based on grid-connected / grid-connected grouping and switching is provided. By exploring the operating potential of active frequency and voltage support under the grid-connected / grid-connected hybrid wind farm multi-machine grid-connected / grid-connected cluster control, based on the grid-connected / grid-connected hybrid wind farm topology, the grid-connected / grid-connected grouping and switching control is applied to the multi-converter control of the grid-connected / grid-connected hybrid wind farm, the active support advantages of the grid-connected wind turbines are combined with the voltage support advantages of the grid-connected wind turbines, and active support is limited on the basis of operation within a wide short-circuit ratio range.

[0038] According to the dynamic process of active and reactive regulation of hybrid wind farms, distributed frequency and voltage control is carried out for the grid-following and grid-forming stations. The grid-following group adopts the active response scheme of leader-follower wind turbines to achieve the maximum frequency support, and the grid-forming wind turbine group adopts a multi-stage active voltage support control scheme; the control parameters of the active support of the wind turbine controller are adaptively changed according to the wind turbine operating status and the grid connection strength changes; through the coupling coefficient feedforward compensation, the problem of the interaction between frequency support and voltage support affecting the system stability and support effect is solved; this method can not only fully tap the voltage source and current source control capabilities of the hybrid wind farms, but also improve the frequency-voltage support capabilities of the hybrid wind farms on the premise of achieving grid stability;

[0039] (2) A grid-following / grid-forming control switching stage is designed to perform active frequency and voltage support control on the hybrid wind farm. If the grid-forming wind turbine group reaches the maximum current inner loop constraint, the grid-forming wind turbine control is switched to the grid-following wind turbine control to avoid overcurrent damage to the converter in the grid-forming type. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 A flow chart of a hybrid wind farm frequency and voltage active support control method based on grouping and switching of follow-up networks provided in an embodiment of the present invention;

[0041] Figure 2 A control block diagram of a hybrid wind farm frequency and voltage active support control method based on grouping and switching of follow-up networks provided in an embodiment of the present invention;

[0042] Figure 3A The grid-connected voltage after a single-phase sudden increase of 600MW of load, the output active power of the grid-following field group, the consistency factor of the grid-following group, the output active power of the grid-forming group, the output reactive power of the grid-forming group and the grid-connected frequency;

[0043] Figure 3B Comparison of the margin of active voltage and frequency support before and after decoupling control is adopted. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0045] In the present invention, the terms "first", "second", etc. (if any) in the present invention and the accompanying drawings are used to distinguish similar objects but not necessarily to describe a specific order or sequence.

[0046] Embodiment 1

[0047] A hybrid wind farm frequency and voltage active support control method based on grid grouping and switching, see Figure 1 , combined with Figure 2-3B , the frequency and voltage active support control method of the hybrid wind farm based on the grouping and switching of the follow-up network in this embodiment is described in detail, and the method includes operations S1-operation S4.

[0048] Operation S1, constructs a clustered distributed active frequency and voltage control strategy for a hybrid wind farm to provide active frequency and voltage support to the power grid. In the hybrid wind farm, the grid-following wind turbine group adopts a leader-follower wind turbine active response method for frequency support, and the grid-building wind turbine group adopts a multi-stage active voltage support method.

[0049] In this embodiment, based on the grid-connected topological structure of the hybrid wind farm, the grid-following type and grid-forming type grouping and switching control are applied to the multi-inverter control of the hybrid wind farm, and the active support advantage of the grid-following type wind turbine is combined with the voltage support advantage of the grid-forming type wind turbine, and the active support is limited on the basis of operating in a wide short-circuit ratio range.

[0050] Specifically, the control process of the grid-type fan is:

[0051]

[0052] The control process of the grid-type fan is:

[0053]

[0054] On the basis of the above control process, the dynamic process of active and reactive regulation of hybrid wind farms is carried out to control the distributed frequency and voltage of the grid-following and grid-forming stations. The grid-following wind turbine group adopts the active response scheme of the leader-follower wind turbine to achieve the maximum frequency support; the grid-forming wind turbine group adopts the control scheme of multi-stage active voltage support.

[0055] The control method of the leading fan and the non-leading fan in the grid-following fan group is:

[0056]

[0057]

[0058] Among them, θ PLL is the output phase angle of the phase-locked loop synchronization loop of the grid-type wind turbine, t is the time, ω is the synchronous frequency of the wind turbine, k pPLL k is the proportional coefficient of the grid-type fan phase-locked loop control, iPLL is the integral coefficient of the grid-type fan phase-locked loop control, u pccq is the q-axis voltage component of the grid-connected wind turbine, i dref_VSC is the d-axis reference value of the inner loop current control of the grid-type fan, i qref_VSC is the q-axis reference value of the inner loop current control of the grid-type fan, k p1 is the first proportionality coefficient, k p2 is the second proportionality coefficient, k i1 is the first integral coefficient, k i2 is the second integral coefficient, P ref is the active reference value of the inverter, P is the actual active value of the inverter, Q ref is the reactive power reference value of the inverter, Q is the actual reactive power value of the inverter, P ref_leader , P ref_i are the active power reference values ​​output by the dominant wind turbine and the i-th non-dominant wind turbine, respectively. MPPT K is the active power of the input grid-type wind turbine maximum power tracking, dr , K in They represent the droop coefficient and integral coefficient of the virtual inertia comprehensive control of the fan, s is the control variable of the controller in the complex frequency domain, f0 is the initial reference value of the frequency of the grid-following fan, f is the actual operating value of the frequency of the grid-following fan, k PPi , k IPi They represent the proportional parameter and integral parameter of consistency control respectively, and x j 、x i are the consistency factors of fans j and i respectively.

[0059] Formula (1) is the general formula for the control process of each grid-type fan. For the leading fan, P in formula (1) is ref The calculation method of P is shown in formula (3). For non-dominant fans, P in formula (1) ref The calculation method of is shown in formula (4).

[0060] The control method of each grid-type fan in the grid-type fan group is:

[0061]

[0062] Among them, E c , δ c ,ω c are the potential amplitude, power angle, and angular frequency of the grid-type wind turbine, t is time, ω0 is the synchronous fundamental frequency angular frequency, P cref , P c , Q cref , Q s They are respectively the active reference value, active actual value, reactive reference value and reactive actual value outputted by the grid-connected wind turbine to the grid connection point, D δ is the damping coefficient, K q , K u are the reactive power coefficient and voltage coefficient of the reactive power voltage control loop, U ref , U s are the grid-connected point voltage reference value and voltage amplitude respectively, J is the inertia coefficient of the virtual synchronous control loop of the grid-connected wind turbine, and J i is the inertia coefficient of the i-th grid-type fan, ω i is the output speed of the i-th grid-type fan, P o_i is the output active power of the i-th grid-type wind turbine, D i is the damping coefficient of the i-th grid-type fan, P GFMi , Q GFMi are respectively the active power reference value and reactive power reference value of the i-th grid-type wind turbine consistency control, N i is the number of grid-type wind turbines in the station, a ij is the active consistency coefficient between the i-th grid-type wind turbine and the j-th grid-type wind turbine, P i , P j are the active power output values ​​of the i-th and j-th grid-type wind turbines, respectively, and b ij is the reactive power consistency coefficient between the i-th grid-type wind turbine and the j-th grid-type wind turbine, Q i , Q j are the reactive power values ​​output by the i-th and j-th grid-type wind turbines, Q o_i is the output reactive power of the i-th grid-type wind turbine.

[0063] Formula (2) is the general formula for the control process of each grid-type fan. For each grid-type fan, P in formula (2) cref , Q cref The calculation methods of P and GFMi , Q GFMi .

[0064] Operation S2, according to the change of wind turbine operating status and grid-connected strength of hybrid wind farm, takes the active support output of hybrid wind farm under cluster distributed active frequency and voltage control strategy not exceeding its maximum support capacity and frequency regulation and voltage regulation are decoupled as the regulation principle, adaptively adjusts the active support control parameters and coupling compensation coefficient in cluster distributed active frequency and voltage control strategy.

[0065] In the clustered distributed active frequency and voltage control strategy, the adaptive adjustment amount of the grid-following wind turbine is:

[0066] ΔP w,i (t) = k wdr,i ×Δf+k win,i ×df / dt

[0067] =[k fdr0 +k adr0 ×(1-x i )]×Δf+[k fin0 +k ain0 ×(1-x i )]×df / dt

[0068] k wdr,i for:

[0069] k wdr,i =(k fdr0 k E +k d0 k E / k L )+((k fdr0 +k adr0 -k fdr )-k d / k L )×(1-x i )

[0070] The adaptive adjustment amount of the grid-type fan is:

[0071] ΔQ ref_GFM =K qu (1-U pcc )

[0072] Among them, ΔP w,i (t) is the compensation power in the adaptive control process of the grid-following fan, k wdr,i is the droop coefficient, Δf is the frequency change between the actual frequency and the initial frequency, k win,i is the inertia coefficient, f is the actual operating value of the frequency of the grid-type fan, k fdr0 , k adr0 are the droop fixed coefficient reference value and adaptive coefficient reference value corresponding to the preset wind farm state, x i is the consistency factor of fan i, kfin0 , k ain0 They are the fixed part coefficient and adaptive part coefficient of the inertia coefficient of the wind farm, ΔQ ref_GFM is the reactive power output value of the grid-type wind turbine, K qu is the reactive voltage support factor, U pcc is the grid-connected voltage of the system.

[0073] The coupling compensation coefficient is:

[0074]

[0075] Among them, K c is the coupling compensation coefficient, K cmax is the maximum value of the coupling compensation coefficient, SCR max is the maximum short-circuit ratio of the wind farm, SCR is the grid-connected short-circuit ratio, K c Adaptive adjustment as SCR changes.

[0076] Operation S3, using the coupling compensation coefficient, performs power feedforward compensation on the wind turbine active reference value and the wind turbine reactive reference value in the adaptively adjusted clustered distributed active frequency and voltage control strategy to form a final clustered distributed active frequency and voltage control strategy.

[0077] Through the coupling coefficient feedforward compensation, the problem of the interaction between frequency support and voltage support affecting the system stability and support effect is solved. The compensation method of power feedforward compensation is:

[0078]

[0079] Among them, P ref_GFL is the active reference value of the grid-type fan, Q ref_GFL P is the reactive power reference value of the grid-following wind turbine, ref_GFM is the active reference value of the grid-type wind turbine, Q ref_GFM is the reactive power reference value of the grid-type wind turbine, P MPPT is the active power of the input grid-type wind turbine maximum power tracking, P sup is the active power increment of the grid-following wind turbine in the active support stage, ΔQ ad is the reactive coupling caused by the increase of active power in the active support process, G QP_GFL (s) is the reactive-active coupling transfer function of the grid-connected wind turbine, Q0 is the initial value of reactive power, K c is the coupling compensation coefficient, ΔP ad is the active power support change value, G PQ_GFL (s) is the active-reactive coupling transfer function of the grid-following wind turbine, P0 is the active reference value of the virtual synchronous control loop of the grid-building wind turbine, G QP_GFM(s) is the reactive-active coupling transfer function of the grid-type wind turbine, G PQ_GFM (s) is the active-reactive coupling transfer function of the grid-type wind turbine.

[0080] Operation S4, using the final clustered distributed active frequency and voltage control strategy, performs active frequency and voltage support control on the hybrid wind farm.

[0081] Preferably, in the frequency and voltage active support control stage of the hybrid wind farm, if the grid-type wind turbine group reaches the maximum current inner loop constraint, the method further includes: switching the grid-type wind turbine control to the grid-following wind turbine control to avoid overcurrent damage to the converter caused by the grid-type wind turbine. The switching method is:

[0082]

[0083] Among them, ω is the synchronous frequency of the fan, ω0 is the synchronous fundamental frequency angular frequency, Δω syn is the compensation value of DC synchronous loop control, K ω is the speed coefficient of the pre-synchronization process, s is the control variable of the controller in the complex frequency domain, θ GFL is the output phase angle of the grid-following control, θ GFM is the output phase angle of the grid-type control, E is the actual value of the output voltage of the fan, E0 is the initial value of the output voltage of the fan, ΔE syn is the compensation amount of internal potential, K E is the electromotive force adjustment coefficient, U is the grid voltage value, i dref is the d-axis current operating reference value of the inner loop current control of the wind turbine grid-side controller, i dref_GFM is the reference value of the d-axis current of the current inner loop of the grid-type wind turbine, Δi is the compensation value of the current loop, K ii is the current compensation coefficient, i dref_GFL It is the current inner loop reference value of the grid-following fan. dref Corresponding to i dref_VSC .

[0084] Further preferably, after switching, when the grid-type wind turbine group is within the maximum current inner loop constraint, the method further comprises: switching back to the grid-type wind turbine control to control the grid-type wind turbine group. The resynchronization process after switching is calculated as:

[0085]

[0086] Among them, ω change 、E change Corresponding to ω c 、E c .

[0087] In order to verify the practicality of this method, this embodiment conducts simulation experiments under different active and reactive power shortages of the hybrid wind farm with / with grid. The control block diagram of the hybrid wind farm with / with grid is as follows: Figure 2 The simulation results are shown in Figure 3A and Figure 3B As shown. Among them, Figure 3A It shows the grid-connected voltage after a single-phase sudden increase of 600MW in load, the output active power of the grid-following field group, the consistency factor of the grid-following group, the output active power of the grid-forming group, the output reactive power of the grid-forming group, and the grid-connected frequency. Figure 3B The figure shows the margin comparison of active voltage and frequency support before and after decoupling control is adopted. Figure 3A and Figure 3B It can be seen that after adopting this method, not only can the voltage source and current source control capabilities of the hybrid wind farm with / with grid connection be fully exploited, but the frequency-voltage support capability of the hybrid wind farm can also be improved under the premise of achieving grid stability.

[0088] The hybrid wind farm frequency and voltage active support control method based on grid-forming grouping and switching provided by the embodiment of the present invention, by exploring the operating potential of active frequency and voltage support under the grid-forming / grid-forming cluster control of multiple machines in the hybrid wind farm, based on the grid-connected topological structure of the hybrid wind farm, applies the grid-forming and grid-forming grouping and switching control to the multi-converter control of the hybrid wind farm, combines the active support advantages of the grid-forming wind turbines with the voltage support advantages of the grid-forming wind turbines, and limits the active support on the basis of operating in a wide short-circuit ratio range. Specifically, the switching process of the hybrid wind farm is divided into a power detection and judgment stage, a grid-forming / grid-forming grouping distributed control stage, a grid-forming / grid-forming adaptive control stage, a grid-forming / grid-forming coupling compensation support stage, and a grid-forming / grid-forming control switching stage. In the power detection and judgment stage, the active power and reactive power changes of the grid-connected side load are detected, and the active voltage and frequency support targets of the following / constructing grid hybrid wind farms are divided into groups according to the changes of active power and reactive power. In the following / constructing grid type group distributed control stage, the dynamic process of active and reactive power regulation of the hybrid following / constructing grid hybrid wind farms is carried out to control the distributed frequency and voltage of the following and constructing grid type stations. The following grid group adopts the leader-follower wind turbine active response scheme to achieve the maximum frequency support, and the constructing grid type wind turbine group adopts the multi-stage active voltage support control scheme. In the following / constructing grid type adaptive control stage, the control parameters of the active support of the wind turbine controller are adaptively changed according to the wind turbine operating status and grid connection strength changes. In the coupling compensation support stage, the coupling coefficient feedforward compensation is used to solve the problem of the interaction between frequency support and voltage support affecting the system stability and support effect. In the following / constructing grid type control switching stage, the grid type with saturated inner loop current is switched to the following grid type control at this stage to avoid overcurrent damage to the converter in the grid type. The proposed control method can not only fully tap the voltage source and current source control capabilities of the grid-connected / grid-connected hybrid wind farm, but also improve the frequency-voltage support capacity of the hybrid wind farm under the premise of grid stability.

[0089] Embodiment 2

[0090] A hybrid wind farm frequency and voltage active support controller based on grouping and switching of a follow-up network comprises: a processor; a memory storing a computer executable program, which, when executed by the processor, enables the processor to execute the above hybrid wind farm frequency and voltage active support control method based on grouping and switching of a follow-up network. The related technical scheme is the same as that of the first embodiment, and will not be repeated here.

[0091] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for active frequency and voltage support control of a hybrid wind farm based on grid grouping and switching, characterized in that: include: Construct a clustered distributed active frequency and voltage control strategy for hybrid wind farms to provide active frequency and voltage support for the power grid. In the hybrid wind farm, the grid-following wind turbine group adopts the leader-follower wind turbine active response method for frequency support, and the grid-building wind turbine group adopts a multi-stage active voltage support method. According to the wind turbine operating status and the change of the grid connection strength of the hybrid wind farm, the active support output of the hybrid wind farm under the clustered distributed active frequency and voltage control strategy shall not exceed its maximum support capacity, and the frequency regulation and voltage regulation shall be decoupled as the regulation principle, and the active support control parameters and coupling compensation coefficients in the clustered distributed active frequency and voltage control strategy shall be adaptively adjusted; The coupling compensation coefficient is used to perform power feedforward compensation on the wind turbine active reference value and wind turbine reactive reference value in the adaptively adjusted clustered distributed active frequency and voltage control strategy to form the final clustered distributed active frequency and voltage control strategy. The final clustered distributed active frequency and voltage control strategy is used to actively support the frequency and voltage of the hybrid wind farm. The control process of the mesh-type fan is as follows: θ PLL is the output phase angle of the phase-locked loop synchronization loop of the grid-type wind turbine, t is the time, ω is the synchronous frequency of the wind turbine, k pPLL k is the proportional coefficient of the phase-locked loop control of the grid-type fan, iPLL is the integral coefficient of the grid-type fan phase-locked loop control, u pccq is the q-axis voltage component of the grid-connected wind turbine, i dref_VSC is the d-axis reference value of the inner loop current control of the grid-type fan, i qref_VSC is the q-axis reference value of the inner loop current control of the grid-type fan, k p1 is the first proportionality coefficient, k p2 is the second proportionality coefficient, k i1 is the first integral coefficient, k i2 is the second integral coefficient, P ref is the active reference value of the inverter, P is the actual active value of the inverter, Q ref is the reactive power reference value of the inverter, Q is the reactive power actual value of the inverter; The adaptive adjustment amount of the grid-type fan is: ΔP w,i (t) is the compensation power in the adaptive control process of the grid-following fan, k wdr,i is the droop coefficient, Δf is the frequency change between the actual frequency and the initial frequency, k win,i is the inertia coefficient, f is the actual operating value of the frequency of the grid-type fan, k fdr0 , k adr0 are the droop fixed coefficient reference value and adaptive coefficient reference value corresponding to the preset wind farm state, x i is the consistency factor of fan i, k fin0 , k ain0 They are the fixed part coefficient and the adaptive part coefficient representing the inertia coefficient of the wind farm respectively.

2. The method for active frequency and voltage support control of a hybrid wind farm based on grouping and switching of wind farm networks according to claim 1, characterized in that: In the constructed clustered distributed active frequency and voltage control strategy, the control method of the leading wind turbine and the non-leading wind turbine in the grid-following wind turbine group is: Among them, P ref_leader , P ref_i are the active power reference values ​​output by the dominant wind turbine and the i-th non-dominant wind turbine, respectively. MPPT K is the active power of the input grid-type wind turbine maximum power tracking, dr , K in They represent the droop coefficient and integral coefficient of the virtual inertia comprehensive control of the fan, s is the control variable of the controller in the complex frequency domain, f0 is the initial reference value of the frequency of the grid-following fan, f is the actual operating value of the frequency of the grid-following fan, k PPi , k IPi They represent the proportional parameter and integral parameter of consistency control respectively, and x j 、x i are the consistency factors of fans j and i respectively.

3. The method for active frequency and voltage support control of a hybrid wind farm based on grouping and switching of wind farm networks according to claim 1, characterized in that: In the constructed clustered distributed active frequency and voltage control strategy, the control process of the grid-type wind turbine is as follows: The control method of each grid-type fan in the grid-type fan group is: Among them, E c , δ c ,ω c are the potential amplitude, power angle, and angular frequency of the grid-type wind turbine, t is time, ω0 is the synchronous fundamental frequency angular frequency, P cref , P c , Q cref , Q s They are respectively the active reference value, active actual value, reactive reference value and reactive actual value outputted by the grid-connected wind turbine to the grid connection point, D δ is the damping coefficient, K q , K u are the reactive power coefficient and voltage coefficient of the reactive power voltage control loop, U ref , U s are the grid-connected point voltage reference value and voltage amplitude respectively, J is the inertia coefficient of the virtual synchronous control loop of the grid-connected wind turbine, and J i is the inertia coefficient of the i-th grid-type fan, ω i is the output speed of the i-th grid-type fan, P o_i is the output active power of the i-th grid-type wind turbine, D i is the damping coefficient of the i-th grid-type fan, P GFMi , Q GFMi are respectively the active power reference value and reactive power reference value of the i-th grid-type wind turbine consistency control, N i is the number of grid-type wind turbines in the station, a ij is the active consistency coefficient between the i-th grid-type wind turbine and the j-th grid-type wind turbine, P i , P j are the active power output values ​​of the i-th and j-th grid-type wind turbines, respectively, and b ij is the reactive power consistency coefficient between the i-th grid-type wind turbine and the j-th grid-type wind turbine, Q i , Q j are the reactive power values ​​output by the i-th and j-th grid-type wind turbines, Q o_i is the output reactive power of the i-th grid-type wind turbine.

4. The method for active frequency and voltage support control of a hybrid wind farm based on grouping and switching of wind farm networks according to claim 1, characterized in that: In the clustered distributed active frequency and voltage control strategy, the adaptive adjustment amount of the grid-type wind turbine is: ΔQ ref_GFM =K qu (1-U pcc ) Among them, ΔQ ref_GFM is the reactive power output value of the grid-type wind turbine, K qu is the reactive voltage support factor, U pcc is the grid-connected voltage of the system.

5. The method for active frequency and voltage support control of a hybrid wind farm based on grouping and switching of wind farm networks according to claim 1, characterized in that: The coupling compensation coefficient is: Among them, K c is the coupling compensation coefficient, K cmax is the maximum value of the coupling compensation coefficient, SCR max is the maximum short-circuit ratio of the wind farm, SCR is the grid-connected short-circuit ratio, K c Adaptive adjustment as SCR changes.

6. The method for active frequency and voltage support control of a hybrid wind farm based on grouping and switching of wind farm networks according to claim 1, characterized in that: The compensation method of power feedforward compensation is: Among them, P ref_GFL is the active reference value of the grid-type fan, Q ref_GFL P is the reactive power reference value of the grid-following wind turbine, ref_GFM is the active reference value of the grid-type wind turbine, Q ref_GFM is the reactive power reference value of the grid-type wind turbine, P MPPT is the active power of the input grid-type wind turbine maximum power tracking, P sup is the active power increment of the grid-following wind turbine in the active support stage, ΔQ ad is the reactive coupling caused by the increase of active power in the active support process, G QP_GFL (s) is the reactive-active coupling transfer function of the grid-following wind turbine, Q0 is the initial value of reactive power, K c is the coupling compensation coefficient, ΔP ad is the active power support change value, G PQ_GFL (s) is the active-reactive coupling transfer function of the grid-following wind turbine, P0 is the active reference value of the virtual synchronous control loop of the grid-building wind turbine, G QP_GFM (s) is the reactive-active coupling transfer function of the grid-type wind turbine, G PQ_GFM (s) is the active-reactive coupling transfer function of the grid-type wind turbine.

7. The method for active frequency and voltage support control of a hybrid wind farm based on grouping and switching of wind farm networks according to any one of claims 1 to 6, characterized in that: In the frequency and voltage active support control stage of the hybrid wind farm, if the grid-type wind turbine group reaches the maximum current inner loop constraint, the method further includes: Switch the grid-type fan control to the grid-following fan control. The switching method is: Among them, ω is the synchronous frequency of the fan, ω0 is the synchronous fundamental frequency angular frequency, Δω syn is the compensation value of DC synchronous loop control, K ω is the speed coefficient of the pre-synchronization process, s is the control variable of the controller in the complex frequency domain, θ GFL is the output phase angle of the grid-following control, θ GFM is the output phase angle of the grid-type control, E is the actual value of the output voltage of the fan, E0 is the initial value of the output voltage of the fan, ΔE syn is the compensation amount of internal potential, K E is the electromotive force adjustment coefficient, U is the grid voltage value, i dref is the d-axis current operating reference value of the inner loop current control of the wind turbine grid-side controller, i dref_GFM is the reference value of the d-axis current of the current inner loop of the grid-type wind turbine, Δi is the compensation value of the current loop, K ii is the current compensation coefficient, i dref_GFL It is the current inner loop reference value of the grid-following fan.

8. The method for active frequency and voltage support control of a hybrid wind farm based on grouping and switching of wind farm networks according to claim 7, characterized in that: After the switching, when the grid-type wind turbine group is within the maximum current inner loop constraint, the method further includes: switching back to the grid-type wind turbine control to control the grid-type wind turbine group.

9. A hybrid wind farm frequency and voltage active support controller based on grid grouping and switching, characterized in that: include: processor; A memory storing a computer executable program, which, when executed by the processor, enables the processor to execute the frequency and voltage active support control method for a hybrid wind farm based on grouping and switching of a follow-up network as described in any one of claims 1-8.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by the processor, the method for active frequency and voltage support control of a hybrid wind farm based on grouping and switching of a follow-up network as described in any one of claims 1 to 8 is implemented.

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