A wind turbine network control system based on adaptive reactive power distribution

Abstract

The present application belongs to the technical field of new energy grid connection, and specifically discloses a wind turbine grid control system based on adaptive reactive power distribution, including: reactive-phase angle control module, integrator and adder; reactive-phase angle control module is used to make a difference based on the reactive power of the wind turbine and the reactive power reference value, and multiply the difference with the droop coefficient, and use the multiplication result as the phase angle deviation signal; the integrator is used to obtain a unified phase angle by integration based on the rated angular frequency of the wind turbine; the adder is used to obtain the reference phase of the AC voltage at the wind turbine port based on the phase angle deviation signal and the unified phase angle. The present application adaptively distributes the reactive power of the wind turbine according to the actual active output of the wind turbine, fully utilizes the commutation capacity of the low-output wind turbine, and avoids the risk of overload of the high-output wind turbine due to excessive reactive power, without relying on communication between wind turbines, and without increasing the rated capacity of the wind turbine, so as to realize the autonomous controllability of the wind turbine and ensure the safe operation of the system.

Description

Technical Field

[0001] The present application belongs to the technical field of new energy grid connection, and more specifically, to a wind turbine grid control system based on reactive power adaptive distribution. Background Art

[0002] The high-voltage direct current (HVDC) system based on diode rectifier (DR) has the advantages of lightweight and high economic benefits, providing a feasible solution for large-scale offshore wind power grid connection. However, due to the uncontrolled characteristics of DR, the DR-HVDC system does not have the ability to build an AC collection network. To solve this problem, additional active equipment such as auxiliary modular multilevel converters (MMCs) can be used, but this will reduce the economic benefits of the DR-HVDC system. The wind turbine grid-side converter has flexible control capabilities and can undertake the task of building an AC collection network voltage. For the DR-HVDC system, the wind turbine grid control includes centralized grid control, distributed phase-locked loop (PLL) type grid control, reactive self-synchronization type grid control, etc.

[0003] Centralized grid control achieves voltage and frequency regulation through active and reactive power control loops, but this method relies on fast communication between wind turbines to achieve AC voltage control at the point of common coupling (PCC). In order to reduce the dependence on communication links, a study proposed distributed PLL-type GFM (grid construction) control to achieve smooth synchronous start-up of wind turbines, and based on Q The droop controller evenly distributes the reactive power of the AC collection network according to the rated capacity of the wind turbine. Considering the impact of the additional PLL on the deterioration of system stability, some literature has proposed a method based on Q The reactive power distribution mechanism of the reactive self-synchronous GFM control of the droop controller is the same as that of the distributed PLL GFM control.

[0004] However, due to the regional differences of offshore wind farms, the active power output between wind turbines is unbalanced. Under the above conventional controlled reactive power distribution mechanism, reactive power is evenly distributed among wind turbines of different outputs, which can easily lead to insufficient utilization of the commutation capacity of low-output wind turbines, while high-output wind turbines face the risk of overload caused by bearing more reactive power. In addition, considering that the AC filter bank (AFB) may have extreme operating conditions such as misoperation in the process of providing DR reactive power compensation, it will lead to an increase in the reactive power surplus or deficit of the offshore AC collection network, which will directly increase the reactive power required by each wind turbine, further exacerbating the overload risk of high-output wind turbines. Summary of the invention

[0005] In view of the defects of the prior art, the purpose of this application is to reasonably allocate reactive power according to the actual active power output of the wind turbine, adapt to the output differences between wind turbines under different working conditions, improve the utilization rate of the commutation capacity of low-output wind turbines, and avoid damage to high-output wind turbines due to overload.

[0006] To achieve the above-mentioned purpose, the present application provides a wind turbine network control system based on reactive adaptive distribution, comprising: a reactive-phase angle control module, an integrator and an adder;

[0007] Reactive power-phase angle control module for reactive power based on wind turbine output Q Gi and reactive power reference values Q Gref , make a difference and add the difference to the droop coefficient k Qp Multiply them and use the result as the phase angle deviation signal Δθ Gi , droop coefficient k Qp is a positive number;

[0008] The integrator is used to obtain a uniform phase angle by integrating the rated angular frequency of the fan. θ N ;

[0009] The adder is used to generate a phase angle deviation signal based on the Δθ Gi and unity phase angle θ N , obtain the reference phase of the AC voltage at the fan port by summing θ Gi , the reference phase of the AC voltage at the fan port θ Gi Used to indicate dq The angular relationship between the coordinate system and the three-phase coordinate system.

[0010] In a possible implementation, the reactive-phase angle control module includes: a reactive-phase angle droop controller, a reactive-phase angle PI controller and an enabling controller;

[0011] Enables the controller to compare the apparent power of the fan S Gi and the apparent power threshold, the apparent power S Gi When the apparent power is less than or equal to the apparent power threshold, the reactive power-phase angle droop controller is controlled to be in the working state, and the reactive power-phase angle PI controller is controlled to be in the stopped state. S GiWhen the power is greater than the apparent power threshold, the reactive power-phase angle droop controller is controlled to be in a stopped state, and the reactive power-phase angle PI controller is controlled to be in a working state;

[0012] The reactive power-phase angle droop controller is used to determine the phase angle deviation signal according to the following equation of reactive power-phase angle droop control mode in the working state. Δθ Gi : ;

[0013] The reactive-phase angle PI controller is used to determine the phase angle deviation signal according to the following equation of the reactive-phase angle PI control mode in the working state: Δθ Gi : ;

[0014] in, Q limit Indicates the limit value of reactive power output, k Qi represents the integral coefficient of the proportional-integral PI controller, s represents a differential operator.

[0015] In a possible implementation, a first-order inertia operator is added to the reactive-phase angle droop control mode, and the equation after adding the first-order inertia operator is:

[0016] ;

[0017] in, represents the first-order inertia operator, s represents the differential operator, k T represents the first-order inertia time constant.

[0018] In a possible implementation, the reactive-phase angle PI controller is also used to: E n A target control moment before being activated, determine the reactive power at the target control moment Q Gi Follow limit value Q limit ;

[0019] The enable signal E n Reactive power at a target control moment before being activated Q Gi If it is greater than or equal to 0, the target control time is set. Q limit is a first limiting value greater than 0;

[0020] Or, in the enable signal En Reactive power at a target control moment before being activated Q Gi When it is less than 0, the target control time is set to Q limit is a second limiting value less than 0.

[0021] In a possible implementation, the reactive-phase angle PI controller is also used to:

[0022] Based on the converter capacity margin of the wind turbine, determine the reactive power range that the wind turbine can bear;

[0023] Based on the reactive power range that the wind turbine can bear, the first limit value and the second limit value are determined.

[0024] In one possible implementation, the enabling controller includes: a comparator and a persistence detector;

[0025] Comparator used to compare apparent power S Gi and the apparent power threshold, the apparent power S Gi When the apparent power is less than or equal to the apparent power threshold, a first control signal is output to the continuous detector. S Gi When the power is greater than the apparent power threshold, a second control signal is output to the continuous detector, and the level of the first control signal is different from the level of the second control signal;

[0026] The continuous detector is used to detect when the duration of the second control signal received is greater than or equal to the continuous detection time threshold. T d In the case of, the reactive power-phase angle droop controller is controlled to be in a stopped state, and the reactive power-phase angle PI controller is controlled to be in a working state; otherwise, when the duration of receiving the first control signal or the second control signal is less than the continuous detection time threshold T d In this case, the reactive power-phase angle droop controller is in working state, and the reactive power-phase angle PI controller is in stopped state.

[0027] In a possible implementation, the comparator is further used to:

[0028] When the reactive power-phase angle droop controller is in operation, set the apparent power threshold to the upper threshold value. S Gup , or when the reactive-phase angle PI controller is in operation, set the apparent power threshold to the lower threshold value S Glow , SGup > S Glow .

[0029] In a possible implementation, the method further includes: a coordinate transformer;

[0030] Coordinate converter for reference phase based on AC voltage at fan port θ Gi , d Axis modulation signal and q Axis modulation signal, execution dq Coordinate system to abc Coordinate system transformation, obtain abc Three-phase control signal.

[0031] In a possible implementation, it further includes: an active power-voltage controller, a voltage controller, and a current controller;

[0032] Active power-voltage controller for wind turbine based active power P Gi and the maximum wind power point captured P Gref , by controlling the active power of the fan P Gi Tracking the maximum wind power point captured P Gref , determine the AC voltage at the fan port v s of d Axis reference voltage v sdref ;

[0033] Voltage controller for use based on d Axis reference voltage v sdref , q Axis reference voltage v sqref , AC voltage at fan port v s of d Shaft voltage v sd AC voltage at fan port v s of q Shaft voltage v sq , through dq The shaft reference voltage is used as a reference to control the fan port AC voltage v s Stable control method to determine the AC current at the fan port i s of d Axis reference currenti sdref and q Axis reference current i sqref ;

[0034] The current controller is used to control the AC current of the fan port. i s of d Axis reference current i sdref and q Axis reference current i sqref And the fan port AC current i s of d Shaft current i sd and q Shaft current i sq , through dq The axis reference voltage is used as a reference to control i s The amplitude control method determines d Axis modulation signal and q Axis modulation signal.

[0035] In one possible implementation, the droop coefficient k Qp The value range is 0.25~5.

[0036] In general, the above technical solutions conceived by this application have the following beneficial effects compared with the prior art:

[0037] (1) This application provides a distribution mechanism for reasonably distributing reactive power according to the actual active power output of the wind turbine. Low-output wind turbines are allocated more reactive power, while high-output wind turbines adaptively bear less reactive power. Based on this distribution mechanism, the utilization rate of the commutation capacity of low-output wind turbines is effectively improved, while the risk of high-output wind turbines being overloaded due to bearing too much reactive power is avoided (the risk of high-output wind turbines being overloaded due to bearing too much reactive power caused by the reactive power equal distribution mechanism in conventional control methods is reduced). Even high-output wind turbines still have a certain capacity margin, which can meet the needs of providing frequency (active power) support for the onshore power grid and improve the capacity controllability of wind turbines with different outputs.

[0038] (2) This application provides Q-θThe wind turbine grid control system with adaptive reactive power distribution can autonomously and reasonably distribute reactive power between wind turbines based on the above distribution mechanism, without relying on communication between wind turbines and increasing the rated capacity of wind turbines. By configuring the enabling controller to complete the mode switching of the reactive-phase control module, it can effectively prevent the high-output wind turbine from being overloaded due to excessive reactive power caused by the reactive power equal distribution mechanism in conventional control methods, and ensure that the output power between wind turbines is within the safety threshold range.

[0039] (3) By designing the upper and lower limits of the apparent power threshold and the continuous detector of the enabling controller, the control mode of the wind turbine can be effectively avoided from frequently switching on and off the reactive power-phase control module due to instantaneous power fluctuations, and the enabling controller can be prevented from malfunctioning under interference such as instantaneous power shocks in the system, thereby enhancing the anti-interference ability of the invented control.

[0040] (4) The grid control system provided in this application has strong applicability and is capable of ensuring the safe and economical operation of the power grid system. It can be extended to the application scenarios of onshore wind power transmission via DR-HVDC system, onshore wind power transmission via cascaded DR-MMC HVDC system, and other types of new energy multi-machine coordinated grid construction scenarios such as photovoltaics. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a structural schematic diagram of a wind turbine network control system based on reactive power adaptive distribution provided in an embodiment of the present application;

[0042] Figure 2 is a schematic diagram of the structure of a reactive power-phase angle control module provided in an embodiment of the present application;

[0043] Figure 3 is a schematic diagram of the structure of an enabling controller provided in an embodiment of the present application;

[0044] Figure 4 It is a schematic diagram of the structure of a simulation model of an offshore wind power transmission system via DR-HVDC provided in an embodiment of the present application;

[0045] Figure 5 It is a schematic diagram of active power when the wind turbine output fluctuates in a wind farm provided by an embodiment of the present application;

[0046] Figure 6 It is a schematic diagram of the total reactive power that a wind farm needs to bear in a malfunction condition where three groups of AFBs are not put into operation before 8 seconds but are fully put into operation after 8 seconds, provided in an embodiment of the present application;

[0047] Figure 7 is a schematic diagram of reactive power distribution between wind turbines with different outputs provided in an embodiment of the present application;

[0048] Figure 8It is a schematic diagram of apparent power between wind turbines with different outputs provided in an embodiment of the present application. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application 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 application and are not used to limit the present application.

[0050] The terms "first" and "second" in the specification and claims herein are used to distinguish different objects rather than to describe a specific order of objects. For example, a first limiting value and a second limiting value are used to distinguish different limiting values ​​rather than to describe a specific order of limiting values.

[0051] In the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0052] In the description of the embodiments of the present application, unless otherwise specified, "multiple" means two or more than two. For example, multiple processing units refer to two or more processing units, etc.; multiple elements refer to two or more elements, etc.

[0053] The embodiments of the present application are described below in conjunction with the drawings in the embodiments of the present application.

[0054] Figure 1 is a schematic diagram of the structure of a wind turbine network control system based on reactive power adaptive distribution provided in an embodiment of the present application, such as Figure 1 As shown, the system includes: a reactive power-phase angle control module (or named as a reactive power to phase angle control module), an integrator and an adder.

[0055] Reactive power-phase angle control module for reactive power based on wind turbine output Q Gi and reactive power reference values Q Gref , make a difference and add the difference to the droop coefficient k Qp Multiply them and use the result as the phase angle deviation signal Δθ Gi , droop coefficient k Qp Is a positive number.

[0056] The integrator is used to obtain a uniform phase angle by integrating the rated angular frequency of the fan. θ N . Figure 1 1 / s represents the transfer function.

[0057] The adder is used to generate a phase angle deviation signal based on the Δθ Gi and unity phase angle θ N , obtain the reference phase of the AC voltage at the fan port by summing θ Gi , the reference phase of the AC voltage at the fan port θ Gi Used to indicate dq The angular relationship between the coordinate system and the three-phase coordinate system.

[0058] It is understandable that each wind turbine may be equipped with the wind turbine grid control system based on reactive power adaptive distribution. Q Gi and reactive power reference values Q Gref , make a difference and add the difference to the droop coefficient k Qp Multiply them and use the result as the phase angle deviation signal Δθ Gi , so it can be determined . Due to the phase angle deviation signal Δθ Gi and unity phase angle θ N , obtain the reference phase of the AC voltage at the fan port by summing θ Gi , so it can be determined . Combined and , the equation of reactive power-phase angle droop control mode can be determined:

[0059] .

[0060] The following is an explanation of the principle of achieving reasonable distribution of reactive power by the reactive-phase angle droop control mode.

[0061] According to the active power transmission characteristics, for any two wind turbines (such as wind turbine 1 and wind turbine 2), the relationship between the phase angle difference of the port AC voltage of the two wind turbines and their active power difference can be expressed as:

[0062] ;

[0063] In the formula, θ G1 and θ G2 are the port AC voltage phase angles of fans 1 and 2 respectively; θ PCC and V PCC are the phase angle and amplitude of the offshore PCC voltage, respectively; V s1 and V s2 They are the effective values ​​of the port AC voltage of fans 1 and 2 respectively; P G1 and P G2 are the active powers of fans 1 and 2 respectively; X ceq1 is the equivalent reactance of the AC submarine cable from wind turbine 1 to the offshore PCC.

[0064] According to the equation of reactive power-phase angle droop control mode, the relationship between the reactive power difference of the two wind turbines and the phase angle difference of the port AC voltage can be expressed as:

[0065] ;

[0066] In the formula, Q G1 and Q G2 are the reactive powers of wind turbines 1 and 2 respectively.

[0067] It can be seen from the above active power transmission characteristics that the voltage phase angle difference between wind turbines is positively correlated with their active power difference. In addition, based on the droop relationship in which the reactive power difference between wind turbines is positively correlated with the voltage phase angle difference in the reactive-phase angle droop control, a control effect in which the reactive power difference output between wind turbines is positively correlated with their active power difference can be achieved. Therefore, the reactive power of the wind turbine can be adaptively allocated according to its actual active output, so that high-output wind turbines can adaptively bear less reactive power, while low-output wind turbines can be allocated more reactive power.

[0068] It should be noted that according to the reactive capacitance characteristics of the offshore AC collection network within the full power range of the wind farm, the reactive power distribution mechanism of the wind turbine can be expressed as high-output wind turbines absorbing less reactive power, and low-output wind turbines absorbing more reactive power.

[0069] Therefore, the wind turbine grid control system based on reactive adaptive distribution provided in the embodiment of the present application can adapt to the output difference between wind turbines under different working conditions, make full use of the commutation capacity of low-output wind turbines (improve the utilization rate of the commutation capacity of low-output wind turbines), and avoid the risk of overload of high-output wind turbines due to excessive reactive power. Even high-output wind turbines still have a certain capacity margin, which can meet the needs of providing frequency (active power) support for onshore power grids. The control system does not need to rely on communication between wind turbines, and does not need to increase the rated capacity of wind turbines, and can achieve the autonomous controllability of wind turbine capacity, ensuring safe and economical operation of the system.

[0070] In addition, the relationship between the reactive power difference and the active power difference between the wind turbines can be expressed as:

[0071] ;

[0072] By changing the droop coefficient k Qp The reactive power difference between wind turbines with different output can be adjusted. For example, the droop coefficient k Qp The value range is 0.25~5. From the above formula, we can see that when the k Qp When the reactive power difference between wind turbines with different outputs decreases, k Qp When the reactive power difference between wind turbines with different output will increase.

[0073] In one possible implementation, Figure 2 is a schematic diagram of the structure of the reactive power-phase angle control module provided in the embodiment of the present application, such as Figure 2 As shown, the reactive-phase angle control module includes: a reactive-phase angle droop controller (or named as a reactive to phase angle droop controller), a reactive-phase angle PI controller (or named as a reactive to phase angle PI controller) and an enabling controller;

[0074] Enables the controller to compare the apparent power of the fan S Gi and the apparent power threshold, the apparent power S Gi When the apparent power is less than or equal to the apparent power threshold, the reactive power-phase angle droop controller is controlled to be in the working state, and the reactive power-phase angle PI controller is controlled to be in the stopped state. S Gi When the power is greater than the apparent power threshold, the reactive power-phase angle droop controller is controlled to be in a stopped state, and the reactive power-phase angle PI controller is controlled to be in a working state;

[0075] The reactive power-phase angle droop controller is used to determine the phase angle deviation signal according to the following equation of reactive power-phase angle droop control mode in the working state. Δθ Gi : ;

[0076] The reactive-phase angle PI controller is used to determine the phase angle deviation signal according to the following equation of the reactive-phase angle PI control mode in the working state: Δθ Gi : ;

[0077] in, Q limit Indicates the limit value of reactive power output, k Qi represents the integral coefficient of the proportional-integral PI controller, s represents a differential operator.

[0078] Optionally, the reactive power-phase angle droop control mode is additionally provided with a first-order inertia operator, and the equation after the addition of the first-order inertia operator is:

[0079] ;

[0080] in, represents the first-order inertia operator, s represents the differential operator, k T represents the first-order inertia time constant.

[0081] Optionally, the reactive-phase angle PI controller is also used to: E n A target control moment before being activated, determine the reactive power at the target control moment Q Gi Follow limit value Q limit ; In the enable signal E n Reactive power at a target control moment before being activated Q Gi If it is greater than or equal to 0, the target control time is set. Q limit is a first limit value greater than 0; or, when the enable signal E n Reactive power at a target control moment before being activated Q Gi When it is less than 0, the target control time is set to Q limit is a second limiting value less than 0.

[0082] Exemplarily, the reactive-phase angle PI controller is also used to: determine the reactive power range that the wind turbine can bear based on the converter capacity margin of the wind turbine; determine the first limit value and the second limit value based on the reactive power range that the wind turbine can bear.

[0083] In one possible implementation, Figure 3 is a schematic diagram of the structure of the enabling controller provided in the embodiment of the present application, such as Figure 3 As shown, the enabling controller includes: a comparator and a continuous detector; the comparator is used to compare the apparent power of the fan S Gi and the apparent power threshold, the apparent power S Gi When the apparent power is less than or equal to the apparent power threshold, a first control signal is output to the continuous detector. S Gi When the power is greater than the apparent power threshold, a second control signal is output to the continuous detector, and the level of the first control signal is different from the level of the second control signal;

[0084] The continuous detector is used to detect when the duration of the second control signal received is greater than or equal to the continuous detection time threshold. T d In the case of, the reactive power-phase angle droop controller is controlled to be in a stopped state, and the reactive power-phase angle PI controller is controlled to be in a working state; otherwise, when the duration of receiving the first control signal or the second control signal is less than the continuous detection time threshold T d In this case, the reactive power-phase angle droop controller is in working state, and the reactive power-phase angle PI controller is in stopped state.

[0085] Optionally, the comparator is also used to set the apparent power threshold to the upper threshold value when the reactive power-phase angle droop controller is in the working state. S Gup , or when the reactive-phase angle PI controller is in operation, set the apparent power threshold to the lower threshold value S Glow , S Gup > S Glow .

[0086] In a possible implementation, the wind turbine network control system based on reactive power adaptive distribution further includes: a coordinate converter;

[0087] Coordinate converter for reference phase based on AC voltage at fan port θ Gi , d Axis modulation signal andq Axis modulation signal, execution dq Coordinate system to abc Coordinate system transformation, obtain abc Three-phase control signal ( abc The three-phase control signal includes a Phase control signal d Ga , b Phase control signal d Gb and c Phase control signal d Gc ).

[0088] Optionally, the wind turbine grid control system further includes: an active power-voltage controller (or named as an active power-to-voltage controller), a voltage controller and a current controller;

[0089] Active power-voltage controller for wind turbine based active power P Gi and the maximum wind power point captured P Gref , by controlling the active power of the fan P Gi Tracking the maximum wind power point captured P Gref , determine the AC voltage at the fan port v s of d Axis reference voltage v sdref ;

[0090] Voltage controller for use based on d Axis reference voltage v sdref , q Axis reference voltage v sqref , AC voltage at fan port v s of d Shaft voltage v sd AC voltage at fan port v s of q Shaft voltage v sq , through dq The shaft reference voltage is used as a reference to control the fan port AC voltage v s Stable control method to determine the AC current at the fan port i s of d Axis reference current isdref and q Axis reference current i sqref ;

[0091] The current controller is used to control the AC current of the fan port. i s of d Axis reference current i sdref and q Axis reference current i sqref And the fan port AC current i s of d Shaft current i sd and q Shaft current i sq , through dq The axis reference voltage is used as a reference to control i s The amplitude control method determines d Axis modulation signal and q Axis modulation signal.

[0092] The wind turbine network control system based on adaptive reactive power distribution provided by the present application is exemplarily described below through three embodiments.

[0093] Embodiment 1

[0094] This embodiment provides a Q-θ Wind power grid control system with adaptive reactive power distribution (reactive power-phase angle), such as Figure 1 The wind turbine grid control system is deployed on the grid-side converter of the wind turbine. The wind turbine grid control system mainly includes: active-voltage controller, reactive-phase angle control module, voltage controller, current controller and coordinate converter (used to execute dq Coordinate system to abc Coordinate system transformation, output abc Three-phase control signal d Ga , d Gb , d Gc to the grid-side converter of the wind turbine). abc The coordinate system is a coordinate system used to describe three-phase AC systems.

[0095] The input of the active power-voltage controller is the active power of the fan P Gi and the maximum wind power point captured P Gref, used to control the active power of the fan P Gi Tracking the maximum wind power point captured P Gref , and generate AC voltage at the fan port v s of( dq coordinate system) d Axis reference voltage v sdref , where the subscript in the electrical variable is i Indicates the serial number of the fan.

[0096] The input of the reactive power-phase angle control module is the reactive power output of the fan Q Gi and its reactive power reference value Q Gref (preset fixed value), used to control each fan to output reactive power according to the fan reactive power distribution mechanism Q Gi , and generate AC voltage at the fan port v s Phase angle deviation signal Δθ Gi ; Rated angular frequency of fan ω 1 (Preset fixed value) generates a uniform phase angle after the integrator θ N , and superimpose the phase angle deviation signal Δθ Gi Generate AC voltage at fan port v s The reference phase angle θ Gi , used for electrical quantities in each controller dq Transformation.

[0097] The input of the voltage controller is AC voltage v s of d Axis reference voltage v sdref and( dq coordinate system) q Axis reference voltage v sqref And AC voltage v s of d Shaft voltage v sd and q Shaft voltage v sq , used to control the port AC voltage v sStabilize and generate AC current at the fan port i s of d Axis reference current i sdref and q Axis reference current i sqref .

[0098] The input of the current controller is the above AC current i s of d Axis reference current i sdref and q Axis reference current i sqref and AC current i s of d Shaft current i sd and q Shaft current i sq , used to control the port AC current i s To achieve limiting (limiting i sdref and i sqref The amplitude of the wind turbine grid-side converter d Axis and q Axis modulation signal.

[0099] Optionally, filters and other links may be added to the input electrical quantities of each controller to improve system performance.

[0100] Optionally, the current controller can be omitted, and the output of the voltage controller is directly used as the current controller of the wind turbine grid-side converter. d Axis and q The axis modulation signal is used to improve the response speed of the AC voltage control at the fan port; the limiting effect of the current controller can be achieved by adopting the virtual impedance method, adding a virtual impedance feedforward branch at the modulation signal, etc.

[0101] Embodiment 2

[0102] This embodiment provides a reactive power-phase angle control module driven by an enabling controller. Figure 2As shown, the reactive-phase control module includes at least two control modes: reactive-phase droop control mode and reactive-phase PI control mode, wherein the reactive-phase droop control mode is the main control mode, which is used to control each wind turbine to adaptively distribute reactive power according to its actual active power output, while the reactive-phase PI control mode is the backup control mode, which is used to accurately limit the transmission capacity of the wind turbine. The equations of the two control modes are:

[0103] ;

[0104] ;

[0105] In the formula, k Qp is the droop coefficient; k Qi is the integral coefficient of the PI controller; Q limit is the limit value of reactive power output (through PI control, the reactive power output of the fan can be Q Gi Limited to Q limit ), s represents a differential operator.

[0106] Optionally, the equations of the two control modes can be supplemented with first-order inertia, filters and other links according to the requirements of enhancing dynamic response inertia and system stability. The equation of reactive-phase angle droop control mode supplemented with first-order inertia can be expressed as:

[0107] ;

[0108] In the formula, k T is the first-order inertia time constant. By adding a first-order inertia link, the negative damping risk caused by the reactive power control link can be effectively reduced and the system stability can be improved.

[0109] Optionally, the switching between the two control modes is performed by an enable signal sent by the enable controller. E n Control, when E n =0, the enabling controller is disabled, and the reactive-phase angle control module operates in the reactive-phase angle droop control mode; when some high-output wind turbines exceed the capacity limit under extreme conditions and activate the enabling controller, E n =1, the reactive power-phase angle control module is switched to the reactive power-phase angle PI control mode, and the reactive power of the high-output wind turbine is accurately controlled to output Q limit, to ensure that the wind turbine is not overloaded, while the remaining low-output wind turbines still distribute reactive power according to the reactive power allocation mechanism.

[0110] For example, consider a fan inverter at rated capacity (1 pu ) configuration, a certain margin is left on the basis of the configuration, and the wind turbine still has the ability to bear reactive power at full active power. pu Taking the converter capacity margin as an example, the reactive power range that the wind turbine can bear is ±0.14 pu Therefore, Q limit The setting can be optimized as follows: If the enable signal E n Before being activated, the reactive power Q Gi When it is greater than or equal to 0, Q limit It can be set to a positive value (the positive value is within the above reactive power range, such as 0.1) to allow the wind turbine to generate reactive power to share the reactive power shortage of the system; otherwise, Q Gi When it is less than 0, Q limit It is set to a negative value (the negative value is within the above reactive power range, such as -0.1) to allow the wind turbine to absorb the reactive surplus of the reactive power sharing system, so as to give full play to the regulating effect of the wind turbine on reactive power fluctuations and ensure the reactive power balance of the wind farm under different working conditions.

[0111] Alternatively, if Figure 3 As shown, the enabling controller includes a comparator and a continuous detector, wherein the input of the comparator is the apparent power of the fan. S Gi and the set apparent power threshold, when S Gi When the apparent power is greater than the set threshold, the comparator outputs a signal of 1, otherwise the output is 0; the output signal of the comparator is used as the input signal of the continuous detector. When the continuous detector is within the set continuous detection time threshold, T d When the input signal is 1, the output enable signal E n If it is 1, it means the fan capacity exceeds the limit, otherwise E n When it is 0, it means the fan output apparent power is within the normal range.

[0112] Exemplarily, the apparent power threshold includes an upper threshold value S Gup and the lower threshold value S Glow .in,S Gup > S Glow ,when E n =0, the apparent power threshold is S Gup ;when E n =1, the apparent power threshold is S Glow , in order to avoid frequent switching of the reactive-phase control module when the instantaneous power of the wind turbine fluctuates.

[0113] In addition, the continuous detection time threshold T d The selection can be based on the withstand time of the wind turbine grid-side converter switch submodule. By setting a continuous detector, it can effectively prevent the enabling controller from malfunctioning under interference such as system instantaneous power impact, thereby enhancing its anti-interference ability. At the same time, when a short circuit fault occurs at the wind turbine outlet, by setting a continuous detection time threshold T d , improve the fan during the fault period T d As much reactive power as possible can still be provided to the fault point to raise the voltage of the offshore PCC, thereby ensuring that the healthy wind turbines can continue to transmit part of their active power to the onshore power grid.

[0114] Embodiment 3

[0115] Figure 4 : is a schematic diagram of the structure of a simulation model of an offshore wind power transmission system via DR-HVDC provided in an embodiment of the present application, such as Figure 4 As shown, this embodiment provides a simulation model of an offshore wind power transmission system via DR-HVDC. The rated active power transmission capacity of the system is 1000MW, and the wind farm consists of a series of 10 10MW wind turbines WT1_1-WT1_10 in parallel, a 400MW equivalent wind turbine WT_2, and a 500MW equivalent wind turbine WT_3. The configured AC filter consists of 4 groups of AC filter groups (AFBs), which provide full reactive power compensation for DR, of which 1 group of AFBs is fixedly connected to the offshore PCC, and the remaining 3 groups of AFBs can be switched in accordance with the reactive power demand changes of DR. Figure 4 middle, v PCC is the AC voltage at the PCC; T DR It is the connecting transformer of DR; i dc is the DR direct current; P DR is the wind power transmitted by DR; v dcDRis the DC voltage of DR; v dcMMC is the DC voltage of the onshore MMC; T MMC It is the connecting transformer of the onshore MMC.

[0116] Figure 5 is a schematic diagram of active power when the wind turbine output fluctuates in a wind farm provided by an embodiment of the present application, based on Figure 4 The PSCAD simulation model shown (Power System Computer Aided Design, abbreviated as PSCAD, is a software tool for power system simulation and design), Figure 5 This is a schematic diagram of active power when the wind turbine output fluctuates in the wind farm, where the active power of WT1_1-WT1_10 is 1 pu At 8s, the active power of WT1_6-WT1_10 remains at 0.95 pu , the active power of WT_2 and WT_3 changes in a larger range.

[0117] Figure 6 This is a schematic diagram of the total reactive power that the wind farm needs to bear when considering the erroneous operation condition that 3 groups of AFBs are not put into operation before 8s but are fully put into operation after 8s, provided by the embodiment of the present application. Considering the extreme operating conditions of the wind farm, the AFBs do not operate with the reactive power demand of the DR. Before 8s, only 1 group of AFBs is put into operation; after 8s, all 4 groups of AFBs are put into operation but cannot be shut down. Figure 6 It can be seen that the total reactive power that the wind farm needs to bear is relatively large, reaching about -0.4 pu Therefore, based on the conventional Q The droop control network control method, in which each wind turbine with different output equally distributes the total reactive power of the wind farm, easily causes overload of the high-output wind turbines WT1_1-WT1_10.

[0118] Figure 7 is a schematic diagram of reactive power distribution between wind turbines with different outputs provided in an embodiment of the present application, Figure 7 It can be seen that under the control of the network control system provided by this application, the reactive power of wind turbines with different outputs is distributed according to their actual active output. The high-output wind turbines WT1_1-WT1_10 can adaptively bear less reactive power, while the low-output wind turbines WT_2 and WT_3 absorb more reactive power. At about 7s, since the apparent power of WT1_1-WT1_10 reaches the upper limit threshold S Gup , and triggered the enabling controller, its reactive power-phase angle control module was switched to reactive power-phase angle PI control mode, and the reactive power of high-output wind turbines WT1_1-WT1_10 was accurately controlled to output Qlimit =0.1 pu , to ensure that the fan is not overloaded, while the other low-output fans still distribute reactive power according to the reactive power allocation mechanism. At 8s, due to Figure 6 The four AFBs shown in the figure are all put into operation, and the wind farm changes from emitting reactive power to absorbing reactive power. Q limit Automatically adjusted to -0.1 pu At about 9 seconds, due to the decrease in active power of WT1_6-WT1_10, its apparent power is lower than the lower threshold. S Glow , the enabling controller of the wind turbine is automatically disabled, and its reactive power-phase angle control module is switched to the reactive power-phase angle droop control mode, and the wind turbine re-participates in the reactive power distribution of the wind farm.

[0119] Figure 8 is a schematic diagram of apparent power between wind turbines with different outputs provided in an embodiment of the present application, Figure 8 is based on Figure 5 The fan active power and Figure 7 The reactive power of the wind turbine is calculated. It can be seen that the wind turbine network control method with adaptive reactive power distribution can realize autonomous capacity regulation without relying on communication between wind turbines. Low-output wind turbines make full use of their commutation capacity and autonomously bear more reactive power. At the same time, combined with the judgment of the enabling controller, it can effectively prevent high-output wind turbines from overloading due to excessive reactive power. Without increasing the rated commutation capacity of the wind turbine, it can ensure safe and economical operation of the wind turbine. Figure 8 When the medium enabling controller is not activated, the high-output wind turbines WT1_1-WT1_10 do not need to equally distribute the reactive power of the wind farm, so they still have a certain capacity margin and can meet the demand of providing frequency (active power) support for the onshore power grid. The above simulation verifies the effectiveness of the wind turbine grid control method proposed in the present invention.

[0120] It should be understood that expressions such as "including" and "may include" that may be used in the present application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In the present application, terms such as "including" and / or "having" may be interpreted as indicating specific characteristics, numbers, operations, constituent elements, components, or combinations thereof, but may not be interpreted as excluding the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0121] The above are only specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A wind turbine network control system based on reactive power adaptive distribution, characterized in that: include: Reactive power-phase angle control module, integrator and adder; The reactive power-phase angle control module is used to control the reactive power output of the fan based on the reactive power output of the fan. and reactive power reference values , make a difference and add the difference to the droop coefficient Multiply them and use the result as the phase angle deviation signal , the droop coefficient is a positive number; The integrator is used to obtain a uniform phase angle by integration based on the rated angular frequency of the fan. ; The adder is used to determine the phase angle deviation signal based on the phase angle deviation signal. and the uniform phase angle , obtain the reference phase of the AC voltage at the fan port by summing , the reference phase of the AC voltage at the fan port Used to indicate dq The angular relationship between the coordinate system and the three-phase coordinate system; The reactive power-phase angle control module includes: a reactive power-phase angle droop controller, a reactive power-phase angle PI controller and an enabling controller; The enabling controller is used to compare the apparent power of the fan and the apparent power threshold, the apparent power When the power is less than or equal to the apparent power threshold, the reactive power-phase angle droop controller is controlled to be in a working state, and the reactive power-phase angle PI controller is controlled to be in a stopped state. When the power is greater than the apparent power threshold, the reactive power-phase angle droop controller is controlled to be in a stopped state, and the reactive power-phase angle PI controller is controlled to be in a working state; The reactive power-phase angle droop controller is used to determine the phase angle deviation signal according to the following equation of reactive power-phase angle droop control mode in the working state: : ; The reactive-phase angle PI controller is used to determine the phase angle deviation signal according to the following equation of the reactive-phase angle PI control mode in the working state: : ; in, Indicates the limit value of reactive power output, represents the integral coefficient of the proportional-integral PI controller, s represents a differential operator.

2. The wind turbine network control system based on reactive power adaptive distribution according to claim 1 is characterized in that: The reactive power-phase angle droop control mode is added with a first-order inertia operator, and the equation after adding the first-order inertia operator is: ； in, represents the first-order inertia operator, s represents the differential operator, represents the first-order inertia time constant.

3. The wind turbine network control system based on reactive power adaptive distribution according to claim 1 is characterized in that: The reactive power-phase angle PI controller is also used to: A target control moment before being activated, determine the reactive power at the target control moment Follow limit value ; The enable signal Reactive power at a target control moment before being activated If it is greater than or equal to 0, the target control time is set. is a first limiting value greater than 0; Or, in the enable signal Reactive power at a target control moment before being activated When it is less than 0, the target control time is set to is a second limiting value less than 0.

4. The wind turbine network control system based on reactive power adaptive distribution according to claim 3 is characterized in that: The reactive power-phase angle PI controller is also used for: Based on the converter capacity margin of the wind turbine, determine the reactive power range that the wind turbine can bear; The first limit value and the second limit value are determined based on a reactive power range that the wind turbine can bear.

5. The wind turbine network control system based on reactive power adaptive distribution according to claim 1 is characterized in that: The enabling controller includes: a comparator and a persistence detector; The comparator is used to compare the apparent power and the apparent power threshold, the apparent power When the apparent power is less than or equal to the apparent power threshold, a first control signal is output to the continuous detector, and when the apparent power When the power level is greater than the apparent power threshold, outputting a second control signal to the continuity detector, wherein the level of the first control signal is different from the level of the second control signal; The duration detector is used to receive the second control signal when the duration is greater than or equal to the duration detection time threshold. In the case of, the reactive power-phase angle droop controller is controlled to be in a stopped state, and the reactive power-phase angle PI controller is controlled to be in a working state; otherwise, when the duration of receiving the first control signal or the second control signal is less than the continuous detection time threshold In this case, the reactive power-phase angle droop controller is controlled to be in a working state, and the reactive power-phase angle PI controller is controlled to be in a stopped state.

6. The wind turbine network control system based on reactive power adaptive distribution according to claim 5 is characterized in that: The comparator is also used to: When the reactive power-phase angle droop controller is in operation, the apparent power threshold is set to the upper threshold value. , or when the reactive-phase angle PI controller is in operation, setting the apparent power threshold to the lower threshold value , > .

7. The wind turbine network control system based on reactive power adaptive distribution according to claim 1 is characterized in that: Also includes: Coordinate transformer; The coordinate converter is used to determine the reference phase of the AC voltage at the fan port based on the reference phase of the AC voltage at the fan port. , d Axis modulation signal and q Axis modulation signal, execution dq Coordinate system to abc Coordinate system transformation, obtain abc Three-phase control signal.

8. The wind turbine network control system based on reactive power adaptive distribution according to claim 7 is characterized in that: Also includes: - voltage controller, voltage controller and current controller; The active power-voltage controller is used to and the maximum wind power point captured , by controlling the active power of the fan Tracking the maximum wind power point captured , determine the AC voltage at the fan port of d Axis reference voltage ; The voltage controller is used based on d Axis reference voltage , q Axis reference voltage , AC voltage at fan port of d Shaft voltage AC voltage at fan port of q Shaft voltage , through dq The shaft reference voltage is used as a reference to control the fan port AC voltage Stable control method to determine the AC current at the fan port of d Axis reference current and q Axis reference current ; The current controller is used to control the AC current of the fan port based on the of d Axis reference current and q Axis reference current And the fan port AC current of d Shaft current and q Shaft current , through dq The axis reference voltage is used as a reference to control The amplitude control method determines d Axis modulation signal and q Axis modulation signal.

9. The wind turbine network control system based on reactive power adaptive distribution according to any one of claims 1 to 8, characterized in that: The droop coefficient The value range is 0.25~5.

Images