Frequency voltage decoupling control method and control system under hybrid wind power plant fault

Abstract

The invention discloses a frequency voltage decoupling control method and a frequency voltage decoupling control system under a fault of a hybrid wind power plant, and belongs to the technical field of wind power generation. First voltage compensation is added to the following net type draught fan and the net constructing type draught fan through the frequency adjusting parameters and the current active power variable quantity; when only the active voltage support is started, first frequency compensation is added to the following net type draught fan and the construction net type draught fan through the voltage adjusting parameters and the current reactive power variable quantity; and when the active frequency support and the active voltage support are started at the same time, adding second voltage compensation and second frequency compensation to the following grid type fan and the constructing grid type fan by using the frequency adjustment parameter, the voltage adjustment parameter, the current active power variable quantity and the current reactive power variable quantity. According to the scheme, active and reactive feed-forward decoupling is carried out on the following / constructing network type fan through decoupling compensation control, and the interaction influence in the frequency voltage supporting process is restrained.

Description

Technical Field

[0001] The present invention belongs to the technical field of wind power generation, and more specifically, relates to a frequency-voltage decoupling control method and control system under the fault of a hybrid wind farm. Background Technique

[0002] As one of the most important renewable energy power generation methods, wind energy has attracted extensive attention around the world. The large-scale wind farms are connected to the AC grid over a long distance, further resulting in the scenario of wind power integration into a weak grid. Currently, the wind turbines widely used in actual wind farms all adopt the grid-following control mode. Existing research shows that the grid-following wind farms have small-signal instability problems under weak grids. In recent years, many scholars have proposed the grid-forming converters as voltage-source control. Compared with the grid-following control, the grid-forming control has better stable operation ability under weak grids. However, existing research shows that the grid-forming control has instability risks under strong grid conditions. The grid-forming wind turbines are expected to jointly form a grid-following-grid-forming hybrid wind farm with the grid-following wind turbines. The hybrid wind farm can combine the voltage-source control advantages of the grid-forming control and the current-source control advantages of the grid-following control. The hybrid wind farm has the advantage of stable operation in a wide short-circuit ratio range and has a broader application prospect in the future.

[0003] However, there are problems that the frequency-voltage dynamics of the grid-following control and the grid-forming control are unclear and it is difficult to directly coordinate the control. In addition, under weak grids, the interactive influence of frequency-voltage control will also cause difficulties in the frequency-voltage coordinated support of the hybrid wind farm.

[0004] Regarding the above problems, the existing research mainly focuses on the active support of the grid-following wind farms in frequency regulation and voltage control respectively. As the wind farms are gradually integrated into the grid, the wind farms need to provide frequency support and voltage support to the grid simultaneously. The current ways for wind farms to participate in frequency / voltage support are relatively single and difficult to meet the flexible frequency / voltage support requirements of the grid. Moreover, the fast frequency control and the active voltage support control are coupled with each other and it is difficult to completely decouple and independently implement their respective functions. Therefore, it is necessary to further study the frequency-voltage coordinated support of the grid-following-grid-forming hybrid wind farms. Summary of the Invention

[0005] Aiming at the above defects or improvement requirements of the existing technology, the present invention provides a frequency-voltage decoupling control method under the fault of a hybrid wind farm, and its purpose is to solve the technical problem that the interactive influence of the frequency-voltage control of the hybrid wind farm is difficult to coordinate and support.

[0006] To achieve the above purpose, according to one aspect of the present invention, a frequency-voltage decoupling control method under the fault of a hybrid wind farm is provided, including:

[0007] When the hybrid wind farm is in a fault state where frequency and voltage support is required, obtain the frequency adjustment parameters and voltage adjustment parameters of the grid-following wind turbines and grid-forming wind turbines in the hybrid wind farm respectively;

[0008] When only active frequency support is started, use the frequency adjustment parameter and the current active power change amount to add a first voltage compensation to both the grid-following wind turbine and the grid-forming wind turbine;

[0009] When only active voltage support is started, use the voltage adjustment parameter and the current reactive power change amount to add a first frequency compensation to both the grid-following wind turbine and the grid-forming wind turbine;

[0010] When both the active frequency support and the active voltage support are started simultaneously, use the frequency adjustment parameter, the voltage adjustment parameter, the current active power change amount, and the current reactive power change amount to add a second voltage compensation and a second frequency compensation to both the grid-following wind turbine and the grid-forming wind turbine.

[0011] Furthermore, the frequency adjustment parameter of the grid-following wind turbine is expressed as:

[0012]

[0013] In the formula, k E represents the grid-following wind turbine frequency regulation ability level coefficient, ω r，i0 represents the initial speed of the grid-following wind turbine, ω r，min represents the minimum limit of the fan rotor speed, ω rref,i0 is the speed of each grid-following wind turbine in the preset state, ΔE represents the grid-following wind farm frequency regulation ability index, ΔE0 represents the initial grid-following wind farm frequency regulation ability index, k wdr，i is the droop coefficient, k fdr and k adr are respectively the droop coefficient and the adaptive coefficient value of the preset grid-following wind turbine, k L represents the accident severity level coefficient, k d represents the adaptive accident change coefficient, x i represents the state information quantity of the i-th grid-following wind turbine, k fdr0 and k adr0 represent the droop fixed coefficient and the adaptive coefficient reference value corresponding to the preset grid-following wind turbine state, k d0 represents the initial value of the grid-following wind turbine adaptive accident change coefficient.

[0014] Furthermore, the voltage adjustment parameter of the grid-following wind turbine is expressed as:

[0015]

[0016] In the formula, Qrefgfl,i Represents the reactive power adjustment parameter during the voltage regulation process of the grid-connected fan, U g Represents the grid-connected voltage amplitude of the grid-connected type, I s Represents the output current of the grid-connected fan, Q ref,0 Represents the initial reactive power parameter of the grid-connected fan. K1 represents the first voltage threshold, and K2 represents the reactive power voltage adjustment coefficient.

[0017] Furthermore, the active frequency support and active voltage support processes of the grid-connected fan are respectively expressed as:

[0018]

[0019] In the formula, P refgfl,i Represents the active power reference value during the active frequency support process of the i-th grid-connected type, P MPPT,i Is the active power input to the maximum power tracking of the i-th grid-connected fan, K dr And K in Respectively represent the droop coefficient and integral coefficient of the virtual inertia comprehensive control of the fan. s represents the differential operator, f0 represents the power frequency, f represents the actual frequency value, I s,i Represents the output current of the i-th grid-connected fan.

[0020] Furthermore, the first voltage compensation corresponding to the grid-connected fan when only the active frequency support is started is expressed as: Q refgfl_sup,i = K c ΔP adgfl,i G PQ (s); The first frequency compensation corresponding to the grid-connected fan when only the active voltage support is started is expressed as: P refgfl_sup,i = K c ΔQ adgfl,i G QP (s);

[0021] The second frequency compensation and the second voltage compensation corresponding to the grid-connected fan are respectively expressed as:

[0022]

[0023] Among them, P refgfl_sup,i Represents the first frequency compensation value of the i-th grid-connected fan, Q refgfl_sup,i Represents the first voltage compensation value of the i-th grid-connected fan, K c Represents the coupling compensation coefficient, ΔQ adgfl,i Represents the change value of the reactive power support of the i-th grid-connected fan, ΔP adgfl,i Represents the change value of the active power support of the i-th grid-connected fan, G QP (s) represents the reactive-active coupling transfer function, G PQ(s) represents the active-reactive coupling transfer function.

[0024] Furthermore, the frequency adjustment parameter of the network-forming wind turbine is expressed as:

[0025]

[0026] In the formula, k E,gfm represents the frequency modulation ability level coefficient of the network-forming wind turbine, c represents the number of network-forming wind turbines, ω gfm，i0 represents the initial rotational speed of the network-forming wind turbine, ω gfmref,i0 is the rotational speed of each network-forming wind turbine in the preset state, ΔE gfm represents the frequency modulation ability index of the grid-following wind farm, ΔE gfm0 represents the initial frequency modulation ability index of the grid-following wind farm, D E,i represents the adaptive frequency adjustment damping coefficient of the network-forming wind turbine, D E,0 represents the initial frequency adjustment damping coefficient of the network-forming wind turbine, J E,i represents the adaptive frequency adjustment inertia coefficient of the network-forming wind turbine, J E,0 represents the initial frequency adjustment inertia coefficient of the network-forming wind turbine.

[0027] Furthermore, the voltage adjustment parameter of the network-forming wind turbine is expressed as:

[0028]

[0029] Among them, K qu (U s ) represents the reactive voltage coefficient, K qu0 represents the initial reactive voltage coefficient, K1 represents the starting threshold of the network-forming wind turbine for low voltage ride-through, K3 represents the starting threshold of the network-forming wind turbine for high voltage ride-through, U s is the grid-connected voltage of the network-forming converter; K qu1 represents the reactive voltage coefficient during the voltage regulation process, P max represents the maximum active power output value, I lim is the current limit value.

[0030] Furthermore, the active support process of the frequency and voltage of the network-forming wind turbine is expressed as:

[0031]

[0032] Among them, J i represents the inertia coefficient of the i-th network-forming wind turbine; ω i represents the angular frequency of the i-th network-forming wind turbine, t represents the time variable, P i represents the active power output value of the i-th network-forming wind turbine, P o，iis the active output power of the i-th network-forming wind turbine, and respectively represent the distribution ratio coefficients of the active power of the i-th and j-th network-forming wind turbines; P GFMi represents the active power value for the coordinated control of each network-forming wind turbine, N i is the number of network-forming wind turbines, a i，j represents the active power consistency coefficient, Q GFMi represents the reactive power value for the coordinated control of each network-forming wind turbine, b i，j represents the reactive power consistency coefficient between the i-th and j-th network-forming wind turbines, Q i represents the reactive power output value of the i-th network-forming wind turbine, Q o_i is the reactive output power of the i-th network-forming wind turbine, and respectively represent the distribution ratio coefficients of the reactive power of the i-th and j-th network-forming wind turbines.

[0033] Furthermore, the first frequency compensation and the first voltage compensation corresponding to the network-forming wind turbine are both expressed as:

[0034] P refgfm_sup,i = K c ΔQ adgfm,i G QP (s);

[0035] Q refgfl_sup,i = 0;

[0036] The second frequency compensation and the second voltage compensation corresponding to the network-forming wind turbine are expressed as:

[0037]

[0038]

[0039] Among them, P refgfm_sup,i and P refgfm_sup2,i represent the first frequency compensation value and the second frequency compensation value of the i-th network-forming wind turbine, K c represents the coupling compensation coefficient, ΔQ adgfm,i represents the change value of the reactive power support of the i-th network-forming wind turbine, Q refgfm_sup,i and Q refgfm_sup2,i represent the first voltage compensation value and the second voltage compensation value of the i-th network-forming wind turbine.

[0040] According to another aspect of the present invention, a control system for a hybrid wind farm is provided, including a memory and a processor, the memory stores a computer program, and when the processor executes the computer program, the steps of the above method are implemented.

[0041] Generally speaking, compared with the prior art, the above technical solution conceived by the present invention can achieve the following beneficial effects:

[0042] (1) The present invention provides a frequency-voltage decoupling control method for a hybrid wind farm under faults. Considering that the essence of frequency-voltage instability is the imbalance between the supply and demand of active power and reactive power, and the large-scale application of converters makes there be a coupling relationship between active and reactive power regulation, further causing mutual influence between frequency regulation and voltage regulation. The adjustment of frequency and voltage is affected by both active power and reactive power at the same time. Therefore, when only active frequency support is started, the first voltage compensation is added to both the grid-following wind turbines and the grid-forming wind turbines by using the frequency adjustment parameter and the current active power change amount; when only active voltage support is started, the first frequency compensation is added to both the grid-following wind turbines and the grid-forming wind turbines by using the voltage adjustment parameter and the current reactive power change amount; when both the active frequency support and the active voltage support are started, the second voltage compensation and the second frequency compensation are added to both the grid-following wind turbines and the grid-forming wind turbines by using the frequency adjustment parameter, the voltage adjustment parameter, the current active power change amount and the current reactive power change amount. This solution performs active-reactive feedforward decoupling on the grid-following / forming wind turbines through decoupling compensation control, suppressing the interaction effect during the frequency-voltage support process. It not only fully exploits the control capabilities of the grid-following / forming wind turbines in the hybrid wind farm to achieve active support for frequency and voltage, but also can expand the output range of the hybrid wind farm's limit support, further promoting the development and utilization of large-scale renewable energy.

[0043] (2) The frequency adjustment parameter of the grid-following wind turbine in this solution is expressed as The advantage of such a design is that the grid-following wind turbines can adaptively adjust the frequency according to their respective frequency modulation capabilities and the severity of the accident, and participate in the support while ensuring the operation stability of the grid-following wind turbines.

[0044] (3) The voltage adjustment parameter of the grid-following wind turbine in this solution is expressed as: The advantage of such a design is that the reactive power output values of the grid-following wind turbines can be distinguished in stages, and the reactive power output of the grid-following wind turbines under different grid connection voltages can be determined. Ensure that the main output is active power under quasi-steady state, and mainly support reactive power under the low voltage ride-through state.

[0045] (4) The active frequency support and active voltage support processes of the grid-following wind turbine in this solution are respectively expressed as: The advantage of such a design is that each grid-following wind turbine autonomously and adaptively adjusts the reference value of the active frequency-voltage support process in real time based on the system frequency-voltage change, reducing the communication requirements between the wind turbines.

[0046] (5) In this solution, when only the active frequency support is started, the first voltage compensation corresponding to the grid-following wind turbine is expressed as: Q refgfl_sup,i = K c ΔP adgfl,i G PQ (s); when only the active voltage support is started, the first frequency compensation corresponding to the grid-following wind turbine is expressed as: P refgfl_sup,i = K c ΔQ adgfl,i G QP (s); The advantage of such a design is that when the grid-following wind turbine participates in frequency support, the influence of the coupling effect generated during the frequency support process on the grid-connected voltage is avoided through coupling compensation; in addition, when the grid-following wind turbine participates in voltage support, the influence of the coupling effect generated during the voltage support process on the system frequency is avoided through coupling compensation.

[0047] (6) The frequency adjustment parameter of the grid-forming wind turbine in this solution is: The advantage of such a design is that each grid-forming wind turbine can adaptively adjust the damping parameter and inertia coefficient in the virtual synchronous control according to its own frequency modulation ability level, and participate in the support while ensuring the operation stability of the grid-forming wind turbine.

[0048] (7) The voltage adjustment parameter of the grid-forming wind turbine in this solution is expressed as:

[0049]

[0050] The advantage of such a design is that the grid-forming wind turbine adaptively adjusts the reactive voltage coefficient in stages according to the real-time change of the grid-connected voltage, realizing the adaptive response to the severity of the accident. In addition, it ensures the active power output level of the grid-forming wind turbine in the quasi-steady state, and gives priority to ensuring the reactive power output ability during the high-voltage and low-voltage crossing processes.

[0051] (8) The active frequency and voltage support process of the grid-forming wind turbine in this solution is expressed as: The advantage of such a design is that it ensures that each grid-forming unit uniformly distributes the active power and reactive power values in the frequency and voltage support process, realizing the reasonable distribution of power. It has better active frequency and voltage support performance compared with the centralized control.

[0052] (8) The first frequency compensation and the first voltage compensation corresponding to the grid-forming wind turbine in this solution are both expressed as: P refgfm_sup,i = K c ΔQ adgfm,i G QP (s); Q refgfl_sup,i= 0; The advantage of such a design is that when the network-forming wind turbine participates in frequency support, the coupling compensation is used to avoid the influence of the coupling effect generated during the frequency support process on the grid-connected voltage. In addition, when the network-forming wind turbine participates in voltage support, the coupling compensation is used to avoid the influence of the coupling effect generated during the voltage support process on the system frequency. The coupling compensation value of the network-forming wind turbine is determined according to the state and control mode of the network-forming wind turbine, so as to realize the adaptive frequency-voltage decoupled support of the network-forming wind turbine. Description of the Drawings

[0053] Figure 1 is the flowchart of the frequency-voltage decoupled control method under the fault of the hybrid wind farm provided in Embodiment 1 of the present invention;

[0054] Figure 2 is the block diagram of the frequency-voltage decoupled control method under the fault of the hybrid wind farm provided in Embodiment 1 of the present invention;

[0055] Figure 3 is the comparison diagram of the system frequency, the active power output of the grid-following type and the network-forming type, the grid-connected point voltage of the system, and the reactive power output value of the network-forming type after the active power of the load suddenly increases by 600 MW and the reactive power suddenly increases by 400 MW provided in Embodiment 1 of the present invention;

[0056] Figure 4 is the comparison diagram of the active power output curves of the grid-following type and the network-forming type after the decoupled active support and the active power output of the grid-following type and the network-forming type of the hybrid wind farm after the decoupled active support after the active power of the load suddenly increases by 600 MW and the reactive power suddenly increases by 400 MW provided in Embodiment 1 of the present invention. Detailed Embodiment

[0057] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used 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.

[0058] Embodiment 1

[0059] This embodiment provides a frequency-voltage decoupled control method under the fault of a hybrid wind farm, as Figure 1 and Figure 2As shown in the figure, it includes: when the hybrid wind farm is in a fault state that requires frequency and voltage support, obtaining the frequency adjustment parameters and voltage adjustment parameters of the grid-connected wind turbines and grid-forming wind turbines in the hybrid wind farm respectively. These two parameters are used as inputs to the controllers of each grid-connected / grid-forming wind turbine, so as to achieve adaptive adjustment of the controller parameters during the frequency and voltage support stage. When only active frequency support is started, the first voltage compensation is added to both the grid-connected wind turbines and the grid-forming wind turbines by using the frequency adjustment parameters and the current active power change; when only active voltage support is started, the first frequency compensation is added to both the grid-connected wind turbines and the grid-forming wind turbines by using the voltage adjustment parameters and the current reactive power change; when both active frequency support and active voltage support are started, the second voltage compensation and the second frequency compensation are added to both the grid-connected wind turbines and the grid-forming wind turbines by using the frequency adjustment parameters, the voltage adjustment parameters, the current active power change, and the current reactive power change.

[0060] Specifically, during the operation of the hybrid wind farm, by detecting the changes in the active power and reactive power of the grid-connected side load, and according to the changes in the active power and reactive power, the target allocation of the grouped active voltage and frequency support of the grid-connected / grid-forming hybrid wind farm is carried out to determine the start control signal. Among them, the control process calculation of the grid-connected / grid-forming in the hybrid wind farm is as follows:

[0061]

[0062] Among them, E c , δ c and ω c are the internal potential amplitude, power angle, and angular frequency of the grid-forming converter, P c , Q s and P cref , Q cref are the active and reactive power output to the grid-connected node and their reference values, U s , U ref are the grid-connected node voltage amplitude and reference value, D δ is the damping coefficient, K q , K u are the reactive and voltage coefficients of the reactive voltage control loop. In addition, ω0 is the synchronous fundamental angular frequency. P ref , Q ref , P, Q are the active and reactive power reference values and actual values of the inverter respectively; i d , i q are the dq-axis components of the PCC point current; i dref , i qref are the reference values of the dq-axis currents output by the GSC side of the wind turbine respectively; k p1 , k i1 , k p2 , k i2 are the parameters of the PI controller respectively.

[0063] As an optional implementation, the frequency adjustment parameters of the grid-connected fan are expressed as:

[0064]

[0065] In the formula, k E represents the frequency modulation ability level coefficient of the grid-connected fan, ω r，i0 represents the initial rotational speed of the grid-connected fan, ω r，min represents the minimum limit of the rotational speed of the fan rotor, ω rref,i0 is the rotational speed of each grid-connected fan in the preset state, ΔE represents the frequency modulation ability index of the grid-connected wind farm, ΔE0 represents the initial frequency modulation ability index of the grid-connected wind farm, k wdr，i is the droop coefficient, k fdr and k adr are respectively the droop coefficient and the adaptive coefficient value of the preset grid-connected fan, k L represents the accident severity level coefficient, k d represents the adaptive accident change coefficient, x i represents the state information quantity of the i-th grid-connected fan, k fdr0 and k adr0 represent the droop fixed coefficient and the adaptive coefficient reference value corresponding to the preset state of the grid-connected fan, k d0 represents the initial value of the adaptive accident change coefficient of the grid-connected fan.

[0066] As an optional implementation, the voltage adjustment parameters of the grid-connected fan are expressed as:

[0067]

[0068] In the formula, Q refgfl,i represents the reactive power adjustment parameter in the voltage regulation process of the grid-connected fan, U g represents the amplitude of the grid-connected voltage of the grid-connected type, I s represents the output current of the grid-connected fan, Q ref,0 represents the initial reactive power parameter of the grid-connected fan, K1 represents the first voltage threshold, and K2 represents the reactive power voltage adjustment coefficient.

[0069] As an optional implementation, the active frequency support and active voltage support processes of the grid-connected fan are respectively expressed as:

[0070]

[0071] In the formula, P refgfl,i represents the active power reference value in the active frequency support process of the i-th grid-connected type, P MPPT,i is the active power input to the maximum power tracking of the i-th grid-connected fan, Kdr With K in respectively representing the droop coefficient and integral coefficient of the virtual inertia comprehensive control of the wind turbine, s represents the differential operator, f0 represents the power frequency, f represents the actual frequency value, and I s,i represents the output current of the i-th grid-following wind turbine. It should be noted that the value of K1 can be 0.9 and its adjacent values, and the value of K2 can be 1.5 and its adjacent values. In addition, the values of both can be determined according to the actual scenario and the operator's experience. The above values are only for illustrative purposes.

[0072] As an optional implementation, when only active frequency support is enabled, the first voltage compensation corresponding to the grid-following wind turbine is expressed as: Q refgfl_sup,i = K c ΔP adgfl,i G PQ (s); when only active voltage support is enabled, the first frequency compensation corresponding to the grid-following wind turbine is expressed as: P refgfl_sup,i = K c ΔQ adgfl,i G QP (s); the second frequency compensation and second voltage compensation corresponding to the grid-following wind turbine are respectively expressed as:

[0073]

[0074] Among them, P refgfl_sup,i represents the first frequency compensation value of the i-th grid-following wind turbine, Q refgfl_sup,i represents the first voltage compensation value of the i-th grid-following wind turbine, K c represents the coupling compensation coefficient, ΔQ adgfl,i represents the reactive power support change value of the i-th grid-following wind turbine, ΔP adgfl,i represents the active power support change value of the i-th grid-following wind turbine, G QP (s) represents the reactive-active coupling transfer function, G PQ (s) represents the active-reactive coupling transfer function.

[0075] As an optional implementation, the frequency adjustment parameter of the grid-forming wind turbine is expressed as:

[0076]

[0077] In the formula, k E,gfm represents the frequency modulation ability level coefficient of the grid-forming wind turbine, c represents the number of grid-forming wind turbines, ω gfm，i0 represents the initial speed of the grid-forming wind turbine, ω gfmref,i 0 is the speed of each grid-forming wind turbine in the preset state, ΔE gfm represents the frequency modulation ability index of the grid-following wind farm, ΔE gfm0Represents the initial frequency regulation ability index of the grid-connected wind farm, D E,i Represents the adaptive frequency adjustment damping coefficient of the grid-forming wind turbine, D E,0 Represents the initial frequency adjustment damping coefficient of the grid-forming wind turbine, J E,i Represents the adaptive frequency adjustment inertia coefficient of the grid-forming wind turbine, J E,0 Represents the initial frequency adjustment inertia coefficient of the grid-forming wind turbine.

[0078] As an alternative implementation, the voltage adjustment parameters of the grid-forming wind turbine are expressed as:

[0079]

[0080] Among them, K qu (U s ) represents the reactive voltage coefficient, K qu0 Represents the initial reactive voltage coefficient, K1 represents the starting threshold of the low voltage ride-through of the grid-forming wind turbine, K3 represents the starting threshold of the high voltage ride-through of the grid-forming wind turbine, U s Is the grid-connected voltage of the grid-forming converter; K qu1 Represents the reactive voltage coefficient during the voltage regulation process, P max Represents the maximum active power output value, I lim Is the current limit value. It should be noted that the value of K1 can be 0.9 and its adjacent values, the value of K3 can be 1.1 and its adjacent values. In addition, the values of the two can be determined according to the actual scenario and the operator's experience. The above values are only for illustrative purposes.

[0081] As an alternative implementation, the active support process of the frequency and voltage of the grid-forming wind turbine is expressed as:

[0082]

[0083] Among them, J i Represents the inertia coefficient of the i-th grid-forming wind turbine; ω i Represents the angular frequency of the i-th grid-forming wind turbine, t represents the time variable, P i Represents the active power output value of the i-th grid-forming wind turbine, P o，i Is the active power output of the i-th grid-forming wind turbine, And Respectively represent the distribution ratio coefficients of the active powers of the i-th and j-th grid-forming wind turbines; P GFMi Represents the active power value for the coordinated control of each grid-forming wind turbine, N i Is the number of grid-forming wind turbines, a i，j Represents the active power consistency coefficient, Q GFMi Represents the reactive power value for the coordinated control of each grid-forming wind turbine, bi，j represents the reactive power consistency coefficient of the i-th and j-th network-forming wind turbines, Q i represents the reactive power output value of the i-th network-forming wind turbine, Q o_i is the reactive power output of the i-th network-forming wind turbine and respectively represent the distribution ratio coefficients of the reactive powers of the i-th and j-th network-forming wind turbines.

[0084] As an alternative implementation, the first frequency compensation and the first voltage compensation corresponding to the network-forming wind turbine are both expressed as:

[0085] P refgfm_sup,i = K c ΔQ adgfm,i G QP (s); Q refgfl_sup,i = 0;

[0086] The second frequency compensation and the second voltage compensation corresponding to the network-forming wind turbine are expressed as:

[0087]

[0088] wherein, P refgfm_sup,i and P refgfm_sup2,i represent the first frequency compensation value and the second frequency compensation value of the i-th network-forming wind turbine, K c represents the coupling compensation coefficient, ΔQ adgfm,i represents the change value of the reactive power support of the i-th network-forming wind turbine, Q refgfm_sup,i and Q refgfm_sup2,i represent the first voltage compensation value and the second voltage compensation value of the i-th network-forming wind turbine.

[0089] To verify the practicability of the present invention, in this embodiment, simulation experiments are carried out under the active and reactive power shortages of different following-network / network-forming hybrid wind farms, and the simulation results are as Figures 3 to 4 shown, wherein Figure 3 (a), (b), (c) and (d) in respectively represent the system frequency, following-network type, network-forming active power output, system grid connection point voltage, and network-forming output reactive power value after a sudden increase of 600 MW in load active power and 400 MW in reactive power; Figure 4 (a) in represents a schematic diagram of the comparison of the active power output curves of the following-network type and the network-forming type after decoupled active support when the load active power suddenly increases by 600 MW and the reactive power suddenly increases by 400 MW; Figure 4 (b) in represents a schematic diagram of the comparison of the active power output of the following-network type and the network-forming type after decoupled active support of the hybrid wind farm when the load active power suddenly increases by 600 MW and the reactive power suddenly increases by 400 MW. From Figures 3 to 4It can be seen that by adopting the frequency-voltage decoupling control method under the fault of the hybrid wind farm proposed by the present invention, not only can the voltage source and current source control capabilities of the grid-connected / grid-forming hybrid wind farm be fully exploited, but also the frequency and voltage of the grid-connected / grid-forming hybrid wind farm can be actively supported, the output range of the hybrid wind farm's limit support is extended, and the development and utilization of large-scale renewable energy are further promoted.

[0090] Embodiment 2

[0091] This embodiment provides a frequency-voltage decoupling control method under the fault of a hybrid wind farm, including a parameter acquisition module, a first compensation module, a second compensation module, and a third compensation module.

[0092] Among them, the parameter acquisition module is used to obtain the respective frequency adjustment parameters and voltage adjustment parameters of the grid-connected wind turbines and the grid-forming wind turbines in the hybrid wind farm when the hybrid wind farm is in a fault state where frequency-voltage support is required. The first compensation module is used to add a first voltage compensation to both the grid-connected wind turbines and the grid-forming wind turbines by using the frequency adjustment parameters and the current active power change amount when only the active frequency support is started. The second compensation module is used to add a first frequency compensation to both the grid-connected wind turbines and the grid-forming wind turbines by using the voltage adjustment parameters and the current reactive power change amount when only the active voltage support is started. The third compensation module is used to add a second voltage compensation and a second frequency compensation to both the grid-connected wind turbines and the grid-forming wind turbines by using the frequency adjustment parameters, the voltage adjustment parameters, the current active power change amount, and the current reactive power change amount when both the active frequency support and the active voltage support are started.

[0093] Embodiment 3

[0094] This embodiment provides a control system for a hybrid wind farm, including a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, the steps of the above method are implemented.

[0095] Those skilled in the art can easily understand that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, 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 frequency-voltage decoupling control method under the fault of a hybrid wind farm, characterized in that Including: When the hybrid wind farm is in a fault state where frequency-voltage support is required, obtain the respective frequency adjustment parameters and voltage adjustment parameters of the grid-following wind turbines and grid-forming wind turbines in the hybrid wind farm; When only active frequency support is started, use the frequency adjustment parameters and the current active power change amount to add a first voltage compensation to both the grid-following wind turbines and the grid-forming wind turbines; When only active voltage support is started, use the voltage adjustment parameters and the current reactive power change amount to add a first frequency compensation to both the grid-following wind turbines and the grid-forming wind turbines; When both the active frequency support and the active voltage support are started simultaneously, use the frequency adjustment parameters, the voltage adjustment parameters, the current active power change amount, and the current reactive power change amount to add a second voltage compensation and a second frequency compensation to both the grid-following wind turbines and the grid-forming wind turbines.

2. The frequency-voltage decoupling control method under faults of the hybrid wind farm according to claim 1, characterized in that The frequency adjustment parameter of the grid-following wind turbine is expressed as: where k E represents the frequency modulation ability level coefficient of the grid-following fan, ω r，i0 represents the initial speed of the grid-following fan, ω r，min represents the minimum limit of the fan rotor speed, ω rref,i0 is the speed of each grid-following fan in the preset state, ΔE represents the frequency modulation ability index of the grid-following wind farm, ΔE0 represents the initial frequency modulation ability index of the grid-following wind farm, k wdr，i is the droop coefficient, k fdr and k adr are respectively the droop coefficient and the adaptive coefficient value of the preset grid-following fan, k L represents the accident severity level coefficient, k d represents the adaptive accident change coefficient, x i represents the state information quantity of the i-th grid-following fan, k fdr0 and k adr0 represent the droop fixed coefficient and the adaptive coefficient reference value corresponding to the preset grid-following fan state, k d0 represents the initial value of the adaptive accident change coefficient of the grid-following fan.

3. The frequency-voltage decoupling control method for a hybrid wind farm under faults according to claim 2, wherein The voltage adjustment parameter of the grid-following wind turbine is expressed as: Wherein, Q refgfl,i represents the reactive power adjustment parameter during the voltage regulation process of the grid-connected fan, U g represents the grid-connected voltage amplitude of the grid-connected fan, I s represents the output current of the grid-connected fan, Q ref,0 represents the initial reactive power parameter of the grid-connected fan, K1 represents the first voltage threshold, and K2 represents the reactive power voltage adjustment coefficient.

4. The frequency-voltage decoupling control method for a hybrid wind farm under faults according to claim 3, characterized in that The active frequency support and active voltage support processes of the grid-following wind turbine are respectively expressed as: Where, P refgfl,i represents the active power reference value during the i-th grid-following active frequency support process, and P MPPT,i is the active power input to the maximum power tracking of the i-th grid-following wind turbine. K dr and K in respectively represent the droop coefficient and integral coefficient of the virtual inertia comprehensive control of the wind turbine. s represents the differential operator, f0 represents the power frequency, f represents the actual frequency value, and I s,i represents the output current of the i-th grid-following wind turbine.

5. The frequency-voltage decoupling control method under the fault of the hybrid wind farm according to claim 4, wherein When only the active frequency support is started, the first voltage compensation corresponding to the grid-following wind turbine is expressed as: Q refgfl_sup,i = K c ΔP adgfl,i G PQ (s); When only the active voltage support is started, the first frequency compensation corresponding to the grid-connected fan is expressed as: P refgfl_sup,i = K c ΔQ adgfl,i G QP (s); The second frequency compensation and the second voltage compensation corresponding to the grid-following wind turbine are respectively expressed as: Among them, P refgfl_sup,i represents the first frequency compensation value of the i-th grid-following fan, Q refgfl_sup,i represents the first voltage compensation value of the i-th grid-following fan, K c represents the coupling compensation coefficient, ΔQ adgfl,i represents the reactive power support change value of the i-th grid-following fan, ΔP adgfl,i represents the active power support change value of the i-th grid-following fan, G QP (s) represents the reactive-active coupling transfer function, G PQ (s) represents the active-reactive coupling transfer function.

6. The frequency-voltage decoupling control method under faults of the hybrid wind farm according to claim 1, wherein The frequency adjustment parameter of the grid-forming wind turbine is expressed as: Where k E,gfm represents the frequency modulation ability level coefficient of the network-forming wind turbine, c represents the number of network-forming wind turbines, ω gfm，i0 represents the initial speed of the network-forming wind turbine, ω gfmref,i0 is the speed of each network-forming wind turbine in the preset state, ΔE gfm represents the frequency modulation ability index of the grid-following wind farm, ΔE gfm0 represents the initial frequency modulation ability index of the grid-following wind farm, D E,i represents the adaptive frequency adjustment damping coefficient of the network-forming wind turbine, D E,0 represents the initial frequency adjustment damping coefficient of the network-forming wind turbine, J E,i represents the adaptive frequency adjustment inertia coefficient of the network-forming wind turbine, J E,0 represents the initial frequency adjustment inertia coefficient of the network-forming wind turbine.

7. The frequency-voltage decoupling control method under the fault of the hybrid wind farm according to claim 6, characterized in that, The voltage adjustment parameter of the grid-forming wind turbine is expressed as: Among them, K qu (U s ) represents the reactive voltage coefficient, K qu0 represents the initial reactive voltage coefficient, K1 represents the starting threshold of the low voltage ride-through of the network-forming wind turbine, K3 represents the starting threshold of the high voltage ride-through of the network-forming wind turbine, U s is the grid-connected voltage of the network-forming converter; K qu1 represents the reactive voltage coefficient during the voltage regulation process, P max represents the maximum active power output value, I lim is the current limit value.

8. The frequency-voltage decoupling control method under the fault of the hybrid wind farm according to claim 7, characterized in that, The active support processes of the frequency and voltage of the grid-forming wind turbine are expressed as: Among them, J i represents the inertia coefficient of the i-th network-forming wind turbine; ω i represents the angular frequency of the i-th network-forming wind turbine, t represents the time variable, P i represents the active power output value of the i-th network-forming wind turbine, Po, i is the active power output of the i-th network-forming wind turbine, and respectively represent the distribution ratio coefficients of the active powers of the i-th and j-th network-forming wind turbines; P GFMi represents the active power value for the consensus control of each network-forming wind turbine, N i is the number of network-forming wind turbines, a i，j represents the active consensus coefficient, Q GFMi represents the reactive power value for the consensus control of each network-forming wind turbine, b i，j represents the reactive consensus coefficient between the i-th and j-th network-forming wind turbines, Q i represents the reactive power output value of the i-th network-forming wind turbine, Q o_i is the reactive power output of the i-th network-forming wind turbine, and respectively represent the distribution ratio coefficients of the reactive powers of the i-th and j-th network-forming wind turbines.

9. The frequency-voltage decoupling control method under the fault of the hybrid wind farm according to claim 7, wherein Both the first frequency compensation and the first voltage compensation corresponding to the grid-forming wind turbine are expressed as: P refgfm_sup,i = K c ΔQ adgfm,i G QP (s); Q refgfl_sup,i ＝0； The second frequency compensation and the second voltage compensation corresponding to the grid-forming wind turbine are expressed as: Among them, P refgfm_sup,i and P refgfm_sup2,i represent the first frequency compensation value and the second frequency compensation value of the i-th network-forming fan, K c represents the coupling compensation coefficient, ΔQ adgfm,i represents the reactive power support change value of the i-th network-forming fan, Q refgfm_sup,i and Q refgfm_sup2,i represent the first voltage compensation value and the second voltage compensation value of the i-th network-forming fan.

10. A control system for a hybrid wind farm, including a memory and a processor, the memory storing a computer program, characterized in that, When the processor executes the computer program, the steps of the method according to any one of claims 1 to 9 are implemented.

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