A virtual inertia adaptive control method for wind and energy storage integrated machine

Abstract

The present invention provides a virtual inertia adaptive control method for a wind-storage integrated machine, which includes obtaining the back electromotive force of a wind turbine generator through a state observer; obtaining an angular frequency estimation value of the back electromotive force through the back electromotive force by a phase-locked loop; obtaining a mechanical speed estimation value according to the angular frequency estimation value; obtaining a corrected speed according to the mechanical speed estimation value and a measured mechanical speed measurement value; correcting the virtual inertia using the corrected speed and the measured state of charge of the energy storage to obtain a corrected virtual inertia; and controlling the frequency response change according to the corrected virtual inertia and the corrected speed. The virtual inertia adaptive control method for a wind-storage integrated machine reduces the high dependence of the power generation system on the speed sensor by adding a state observer, realizes the stable operation of the wind turbine generator when there is a large measurement error in the mechanical speed or the sensor fails, and improves the network connection and robustness of the wind power generation system.

Description

Technical Field

[0001] The present invention relates to the technical field of wind-storage integrated machine, and in particular to a virtual inertia adaptive control method for a wind-storage integrated machine. Background Art

[0002] As large-scale wind power generation systems are integrated into the power grid, traditional renewable energy power stations are unable to provide effective and reliable grid support capabilities in the face of frequency / voltage disturbances caused by high proportions of renewable energy access to the grid. Since mechanical speed sensors in wind power generation systems produce measurement errors and fail, grid stability is affected. At the same time, the traditional control performance of maximum power point tracking (MPPT) based on power decoupling is heavily dependent on the speed measurement of wind turbines.

[0003] Adding energy storage to wind power generation systems and adopting virtual synchronous control strategies can effectively improve the inertia support capacity of wind power generation systems for the power grid. How to improve the friendly grid connection and reliability of wind-storage integrated machines based on virtual synchronous machine control strategies has become an urgent problem to be solved. Summary of the invention

[0004] The purpose of the present invention is to provide a virtual inertia adaptive control method for a wind-storage integrated machine, which can improve the grid connection quality and robustness of a wind power generation system.

[0005] The embodiments of the present invention can be implemented in the following ways:

[0006] A virtual inertia adaptive control method for a wind turbine and energy storage system, comprising obtaining a back electromotive force of a wind turbine generator through a state observer;

[0007] The phase-locked loop obtains an angular frequency estimation value of the back electromotive force through the back electromotive force;

[0008] Obtaining a mechanical rotation speed estimate value according to the angular frequency estimate value;

[0009] Obtaining a corrected speed according to the estimated mechanical speed value and the measured mechanical speed value;

[0010] The virtual inertia is corrected using the corrected rotation speed and the measured state of charge of the energy storage to obtain a corrected virtual inertia;

[0011] The frequency response changes according to the modified virtual inertia and the modified rotation speed control.

[0012] Optionally, the formula for obtaining the estimated mechanical speed value according to the estimated angular frequency value is:

[0013]

[0014] Where p is the number of pole pairs of the permanent magnet direct drive generator, is the estimated angular frequency, Estimated machine speed.

[0015] Optionally, a formula for obtaining a corrected speed according to the estimated mechanical speed value and the measured mechanical speed value is:

[0016]

[0017] Among them, ω′ m To correct the speed; is the estimated mechanical speed, ω m is the mechanical speed measurement value, λ1 is the weight of the mechanical speed estimation value; λ2 is the weight of the mechanical speed measurement value; λ1+λ2=1.

[0018] Optionally, when the mechanical speed measurement value is less than a preset speed, λ1 is set less than λ2; when the mechanical speed measurement value is greater than the preset speed, λ1 is set greater than λ2; when the speed sensor used to obtain the mechanical speed measurement value fails, λ1=1, λ2=0.

[0019] Optionally, the preset rotation speed is one third of the rated rotation speed of the wind storage machine.

[0020] Optionally, the virtual inertia is corrected using the corrected rotation speed and the measured state of charge of the energy storage to obtain a formula for corrected virtual inertia:

[0021]

[0022] J=J0+J′

[0023] Wherein, J is the virtual inertia; J0 is the virtual inertia parameter of the wind-storage integrated machine set when the energy storage charge state is 100%; J′ is the virtual inertia correction value; is the estimated value of mechanical speed; ω m is the mechanical speed measurement value; SOC is the charge state of the energy storage.

[0024] Optionally, a formula for controlling the frequency response change according to the modified virtual inertia and the modified speed is:

[0025]

[0026] Among them, ω′ m is the corrected speed; D is the damping coefficient; T m is the generator mechanical torque; T e is the electromagnetic torque of the generator; ω0 is the rated mechanical speed.

[0027] Optionally, the wind and energy storage integrated machine virtual inertia adaptive control method further includes:

[0028] The power output by the energy storage is corrected according to the estimated mechanical speed value and the measured mechanical speed value.

[0029] Optionally, a formula for correcting the power output by the energy storage according to the estimated mechanical speed value and the measured mechanical speed value is:

[0030]

[0031] Among them, P′ Batref is the corrected energy storage power reference value; P Batref The control system directly uses the speed measurement value and obtains the active power reference value after passing through the frequency-active power droop link; P Bat It is the actual power measurement value emitted by the energy storage; is the estimated value of mechanical speed; ω m It is the measured value of mechanical speed.

[0032] Optionally, the wind and energy storage integrated machine virtual inertia adaptive control method further includes:

[0033] When the state of charge of the energy storage is less than or equal to 10%, the discharge of the energy storage unit is restricted;

[0034] When the state of charge of the energy storage is greater than or equal to 90%, charging of the energy storage unit is restricted.

[0035] The beneficial effects of the virtual inertia adaptive control method of the wind and energy storage integrated machine provided by the embodiment of the present invention include:

[0036] The embodiment of the present invention provides a virtual inertia adaptive control method for a wind-storage integrated machine, which includes obtaining the back electromotive force of a wind turbine generator through a state observer; obtaining an angular frequency estimation value of the back electromotive force through the back electromotive force by a phase-locked loop; obtaining a mechanical speed estimation value according to the angular frequency estimation value; obtaining a corrected speed according to the mechanical speed estimation value and the measured mechanical speed measurement value; correcting the virtual inertia using the corrected speed and the measured state of charge of the energy storage to obtain a corrected virtual inertia; and controlling the frequency response change according to the corrected virtual inertia and the corrected speed. The virtual inertia adaptive control method for a wind-storage integrated machine reduces the high dependence of the power generation system on the speed sensor by adding a state observer, realizes the stable operation of the wind turbine generator when there is a large measurement error in the mechanical speed or the sensor fails, and improves the network connection and robustness of the wind power generation system. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The above features and advantages of the present invention can be better understood after reading the detailed description of the embodiments of the present disclosure in conjunction with the following drawings. In the drawings, the components are not necessarily drawn to scale, and components with similar related properties or features may have the same or similar reference numerals.

[0038] Figure 1 A step diagram showing a method for adaptively controlling virtual inertia of a wind and energy storage integrated machine according to one aspect of the present invention is shown;

[0039] Figure 2 A structural block diagram showing a mechanical rotation speed estimation value obtained in a wind-storage integrated machine according to one aspect of the present invention is shown;

[0040] Figure 3 A block diagram of a virtual synchronous machine control provided by this embodiment according to one aspect of the present invention is shown;

[0041] Figure 4 A block diagram of a process for correcting the power output by energy storage provided according to one aspect of the present invention is shown. DETAILED DESCRIPTION

[0042] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. Note that the aspects described below in conjunction with the accompanying drawings and specific embodiments are only exemplary and should not be construed as limiting the scope of protection of the present invention in any way.

[0043] In the description of the present invention, it should be noted that if the terms "upper", "lower", "inside", "outside", "vertical" and the like appear, the orientation or position relationship indicated is based on the orientation or position relationship shown in the drawings, or is the orientation or position relationship in which the product of the invention is usually placed when used, rather than indicating or implying that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0044] At the same time, it should be noted that the terms "first", "second", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0045] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified or limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, an integral connection, or a detachable connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or the internal communication of two components, etc. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0046] Figure 1The following is a step diagram of the virtual inertia adaptive control method of the wind and energy storage integrated machine provided in this embodiment. Figure 2 A structural block diagram of obtaining a mechanical speed estimation value in a wind-storage integrated machine provided in an embodiment, Figure 3 This is a virtual synchronous machine control block diagram provided in this embodiment. Please refer to Figure 1-Figure 3 This embodiment provides a method for adaptively controlling virtual inertia of a wind and energy storage integrated machine, which includes:

[0047] S01: Obtain the back electromotive force of the wind turbine generator through the state observer.

[0048] In this embodiment, taking a permanent magnet synchronous direct-drive wind power generation system as an example, the process of obtaining the back electromotive force of a wind generator through a state observer is described. The permanent magnet synchronous direct-drive wind power generation system is one of the commonly used grid-connected systems. The working characteristics of the permanent magnet synchronous direct-drive wind power generation system lead to the decoupling of the inertia interaction between the wind power generation system and the power grid, further reducing the inertia support capacity of the wind power. Adding energy storage to the wind power generation system and adopting a virtual synchronous control strategy can effectively improve the inertia support capacity of the wind power generation system for the power grid. In this embodiment, the state observer is a mechanical speed sliding mode observer. At the same time, before executing step S01, it can also include a step of designing the mechanical speed sliding mode observer. According to the Lyapunov stability principle, the feedback gain of the observer is designed to ensure the stability of the sliding mode observer. When the current observation error of the mechanical speed observer tends to 0, the feedback input of the mechanical speed sliding mode observer is approximately equivalent to the back electromotive force of the stator of the permanent magnet synchronous generator.

[0049] Specifically, the process includes:

[0050] It is known that the stator winding voltage equation of a permanent magnet synchronous motor is:

[0051]

[0052] Among them, i α,βs is the output current of the generator stator winding; u α,βs is the terminal voltage of the generator stator winding; e α,βs is the back electromotive force of the stator winding; L s is the inductance of the stator winding; R s is the equivalent resistance of the stator winding.

[0053] Its matrix form is:

[0054]

[0055] Among them, A and B are system matrices; x = [i αs i βs ] T is the state vector; u=[u αsu βs ] T is the input vector; is the perturbation input vector.

[0056] The mechanical speed sliding mode observer is used to observe the mechanical speed of the rotor. The sliding mode observation equation is as follows:

[0057]

[0058] in, is the observed value, sat is the saturation function; L SMO is the gain of the back-EMF sliding mode observer.

[0059] When the current observation error When it approaches zero, the mechanical speed sliding mode observer will constrain the state trajectory near the sliding mode surface, that is:

[0060]

[0061] In order to ensure the stability of the sliding mode observer, the Lyapunov function is selected as follows:

[0062]

[0063] By combining the sliding surface S(x) and the Lyapunov function, the range of the feedback gain LSMO that makes the sliding mode observer stable can be obtained as:

[0064] L SMO <-max(|e αs |,|e βs |)

[0065] When the observation error of the mechanical speed sliding mode observer When the sliding surface S(x)=0 is reached, the feedback input L of the mechanical speed sliding mode observer is SMO sat(e x ) is approximately equivalent to the observed value of the stator back electromotive force of the generator The back EMF observation value after filtering is obtained by using a first-order low-pass filter (LPF):

[0066]

[0067] S02: The phase-locked loop obtains an angular frequency estimation value of the back electromotive force through the back electromotive force.

[0068] The back electromotive force obtained Input to the phase-locked loop, and obtain the angular frequency estimate of the back electromotive force through the phase-locked loop

[0069] S03: Obtain a mechanical rotation speed estimate value according to the angular frequency estimate value.

[0070] The relationship between the estimated angular frequency and the estimated mechanical speed satisfies the following formula:

[0071]

[0072] Where p is the number of pole pairs of the permanent magnet direct drive generator, is the estimated angular frequency, Estimated machine speed.

[0073] S04: Obtain a corrected speed according to the estimated mechanical speed value and the measured mechanical speed value.

[0074] In order to improve the control accuracy of the wind turbine speed, the formula for correcting the speed measurement value of the speed control link using the mechanical speed estimation value is as follows:

[0075]

[0076] Among them, ω′ m To correct the speed; is the estimated mechanical speed, ω m is the mechanical speed measurement value, λ1 is the weight of the mechanical speed estimation value; λ2 is the weight of the mechanical speed measurement value; λ1+λ2=1.

[0077] The calculated corrected speed is used to replace the mechanical speed measurement value measured in the speed control link to realize the MPPT (maximum power tracking) operation of the wind turbine and improve the utilization rate of wind energy. At the same time, by setting the values ​​of λ1 and λ2 specifically, the weight of the mechanical speed measurement value in the corrected speed is adjusted, which reduces the dependence of the wind power generation system on the speed sensor, thereby reducing the impact of the speed sensor on the grid connection of the wind-storage integrated machine when there is a large error or the sensor fails, which helps to improve the friendly grid connection and reliability of the wind-storage integrated machine.

[0078] Optionally, when the mechanical speed measurement value is less than the preset speed, λ1 is set to be less than λ2; when the mechanical speed measurement value is greater than the preset speed, λ1 is set to be greater than λ2; when the speed sensor used to obtain the mechanical speed measurement value fails, λ1=1, λ2=0. Specifically, when the mechanical speed measurement value is less than the preset speed, λ1=0.2, λ2=0.8 are set; when the mechanical speed measurement value is greater than the preset speed, λ1=0.7, λ2=0.3 are set. Optionally, the preset speed is one third of the rated speed.

[0079] S05: Correcting the virtual inertia by using the corrected rotation speed and the measured nuclear power state of the energy storage to obtain a corrected virtual inertia.

[0080] J=J0+J′

[0081]

[0082] Wherein, J is the virtual inertia; J0 is the virtual inertia parameter of the wind-storage integrated machine set when the energy storage charge state is 100%; J′ is the virtual inertia correction value; is the estimated value of mechanical speed; ω m is the mechanical speed measurement value; SOC is the charge state of the energy storage.

[0083] The virtual inertia value in the virtual synchronous control is adaptively adjusted according to the energy storage SOC (i.e., the virtual inertia is corrected) so that the energy storage can participate in the inertia support process of the wind turbine to the maximum extent and ensure that the energy storage device operates stably within a reasonable SOC range.

[0084] S06: Control the frequency response change according to the corrected virtual inertia and the corrected speed.

[0085] The formula for changing the frequency response based on the corrected virtual inertia and corrected speed control is:

[0086]

[0087] Among them, ω′ m is the corrected speed; D is the damping coefficient; T m is the generator mechanical torque; T e is the electromagnetic torque of the generator; ω0 is the rated mechanical speed.

[0088] Figure 3 The structural block diagram of the virtual inertia correction and control in the virtual synchronous control of the wind-storage integrated machine is shown. Figure 3 The control model of the virtual synchronous machine of the grid-side converter and its subsequent control are conventional methods of virtual synchronous control strategy, such as Figure 3 As shown in the figure, the corrected virtual inertia and the active power P of the wind-storage integrated machine based on the virtual synchronous control strategy are ref is input into the grid-side converter virtual synchronous machine control model, and the grid-side converter virtual synchronous machine control model outputs the back electromotive force amplitude e of the virtual synchronous generator VSG and the back EMF phase Q of the virtual synchronous generator VSG , e VSG and Q VSG Input to the voltage and current double closed loop, the voltage and current double closed loop outputs the switching signal S of the grid-side converter of the wind and energy storage integrated machine abc , thereby realizing the control of the wind storage integrated machine.

[0089] S07: Correcting the power output by the energy storage according to the estimated mechanical speed value and the measured mechanical speed value.

[0090] In order to ensure that energy storage participates in the support of the grid frequency by the wind-storage integrated machine and ensures the safe and stable operation of energy storage, the power output of energy storage can be corrected according to the estimated value and measured value of the mechanical speed. The correction process is as follows: Figure 4 As shown, where f n is the rated value of the grid frequency, f g is the measured value of the grid frequency, k is the droop coefficient of the frequency-active power droop control, and f n 、f g And k get the active power reference value P Batref .

[0091] The formula for correcting the power output of energy storage is:

[0092]

[0093] Among them, P′ Batref is the corrected energy storage power reference value; P Batref is the active power reference value; P Bat It is the actual power measurement value emitted by the energy storage; is the estimated value of mechanical speed; ω m It is the measured value of mechanical speed.

[0094] In order to ensure the rational use of energy storage devices while reducing excessive charging and discharging of energy storage units, so as to extend the life of energy storage, the SOC characteristics of the energy storage units should be fully considered in the virtual inertia control process of the wind-storage integrated machine to avoid overcharging and over-discharging.

[0095] Specifically, when the state of charge of the energy storage is less than or equal to 10%, the discharge of the energy storage unit is restricted; when the state of charge of the energy storage is greater than or equal to 90%, the charging of the energy storage unit is restricted. At the same time, when the state of charge of the energy storage is greater than 10% and less than 90%, the energy storage system is charged and discharged normally.

[0096] The method for adaptive control of virtual inertia of an integrated wind and energy storage machine provided in an embodiment of the present invention estimates the rotational speed by introducing a state observer, corrects the virtual inertia using the rotational speed estimation value, and performs subsequent control processes, thereby realizing adaptive control of the integrated wind and energy storage machine. In addition, the power generation system is highly dependent on the rotational speed sensor, thereby realizing stable operation of the wind turbine when a large measurement error occurs in the mechanical rotational speed or the sensor fails, thereby improving the network connection friendliness and robustness of the wind power generation system.

[0097] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technology in the field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A virtual inertia adaptive control method for a wind and energy storage integrated machine, characterized in that: The virtual inertia adaptive control method of the wind and energy storage integrated machine includes: The back electromotive force of the wind turbine generator is obtained through the state observer; The phase-locked loop obtains an angular frequency estimation value of the back electromotive force through the back electromotive force; Obtaining a mechanical rotation speed estimate value according to the angular frequency estimate value; Obtaining a corrected speed according to the estimated mechanical speed value and the measured mechanical speed value; The virtual inertia is corrected using the corrected rotation speed and the measured state of charge of the energy storage to obtain a corrected virtual inertia; Controlling a frequency response change according to the modified virtual inertia and the modified speed; The formula for obtaining the estimated mechanical speed based on the estimated angular frequency is: Where p is the number of pole pairs of the permanent magnet direct drive generator, is the estimated angular frequency, Estimated mechanical speed; The formula for obtaining the corrected speed according to the estimated mechanical speed value and the measured mechanical speed value is: in, To correct the speed; is the estimated mechanical speed, is the mechanical speed measurement value, is the weight of the estimated mechanical speed; is the weight of the mechanical speed measurement value; ; The virtual inertia is corrected using the corrected speed and the measured state of charge of the energy storage to obtain a formula for corrected virtual inertia: Wherein, J is the virtual inertia; J0 is the virtual inertia parameter of the wind-storage integrated machine set when the energy storage charge state is 100%; is the virtual inertia correction value; is the estimated value of mechanical speed; is the mechanical speed measurement value; SOC is the charge state of the energy storage; The formula for controlling the frequency response change according to the modified virtual inertia and the modified speed is: in, is the corrected speed; D is the damping coefficient; T m is the generator mechanical torque; T e is the electromagnetic torque of the generator; is the rated mechanical speed.

2. The virtual inertia adaptive control method of the wind and energy storage integrated machine according to claim 1 is characterized in that: When the mechanical speed measurement value is less than the preset speed, set Less than When the mechanical speed measurement value is greater than the preset speed, set Greater than ; When the speed sensor used to obtain the mechanical speed measurement value fails, set =1, =0.

3. The virtual inertia adaptive control method of the wind and energy storage integrated machine according to claim 2 is characterized in that: The preset rotation speed is one third of the rated rotation speed of the wind storage integrated machine.

4. The virtual inertia adaptive control method of the wind and energy storage integrated machine according to claim 1 is characterized in that: The virtual inertia adaptive control method of the wind and energy storage integrated machine also includes: The power output by the energy storage is corrected according to the estimated mechanical speed value and the measured mechanical speed value.

5. The virtual inertia adaptive control method of the wind and energy storage integrated machine according to claim 4 is characterized in that: The formula for correcting the power output of the energy storage according to the estimated mechanical speed value and the measured mechanical speed value is: Among them, P Batref is the corrected energy storage power reference value; The control system directly uses the speed measurement value and obtains the active power reference value through the frequency-active power droop link; It is the actual power measurement value emitted by the energy storage; is the estimated value of mechanical speed; It is the measured value of mechanical speed.

6. The virtual inertia adaptive control method of the wind and energy storage integrated machine according to claim 1 is characterized in that: The virtual inertia adaptive control method of the wind and energy storage integrated machine also includes: When the state of charge of the energy storage is less than or equal to 10%, the discharge of the energy storage unit is restricted; When the state of charge of the energy storage is greater than or equal to 90%, charging of the energy storage unit is restricted.

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