CN113090437A - Direct-drive wave energy power generation maximum wave energy accurate tracking control method based on spring resonance assistance - Google Patents
Direct-drive wave energy power generation maximum wave energy accurate tracking control method based on spring resonance assistance Download PDFInfo
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
- F03B—MACHINES OR ENGINES FOR LIQUIDS
- F03B13/00—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates
- F03B13/12—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy
- F03B13/14—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
- F03B—MACHINES OR ENGINES FOR LIQUIDS
- F03B15/00—Controlling
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F17/00—Digital computing or data processing equipment or methods, specially adapted for specific functions
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- G06F30/20—Design optimisation, verification or simulation
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
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- F05B2220/00—Application
- F05B2220/70—Application in combination with
- F05B2220/706—Application in combination with an electrical generator
- F05B2220/7066—Application in combination with an electrical generator via a direct connection, i.e. a gearless transmission
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/30—Energy from the sea, e.g. using wave energy or salinity gradient
Abstract
The invention provides a spring resonance assistance-based direct-drive wave energy power generation maximum wave energy accurate tracking control method, which comprises the steps of constructing a mathematical model of a direct-drive wave energy power generation device; designing a mixed finite time tracking control strategy; and carrying out stability analysis on the designed mixed finite time tracking control strategy. Aiming at the influence of the ocean complex environment on the power generation process, a finite time disturbance observer is adopted to quickly compensate the environmental disturbance. Aiming at a motor control system, a d-axis current finite time regurator and a nonsingular terminal sliding mode q-axis current controller based on a finite time disturbance observer are respectively designed to accurately realize the resonance of a direct-drive wave energy power generation device buoy and waves under a complex environment and achieve the maximum wave energy tracking. Simulation research and comprehensive comparison show that the proposed hybrid finite time tracking control strategy has remarkable rapid adaptability and accurate maximum wave energy tracking performance under the condition of disturbance and a spring resonance auxiliary system.
Description
Technical Field
The invention relates to the technical field of new energy application, in particular to a direct-drive wave energy power generation maximum wave energy accurate tracking control method based on spring resonance assistance.
Background
On the maximum wave energy tracking control execution device of the direct drive type wave energy power generation device, the wave energy absorption efficiency of the direct drive type wave energy power generation device under the variable wave environment caused by the seasonality in the same sea area can be effectively improved by the tide effect compensation system in consideration of the wave change caused by the seasonality tide. In the prior art, an Archimedes direct-drive wave energy power generation device is designed, the Archimedes direct-drive wave energy power generation device is a special air cylindrical cavity structure, and the volume of gas can be changed according to wave pressure when a wave peak and a wave valley move along with waves, so that the Archimedes direct-drive wave energy power generation device can better adapt to adverse effects caused by large-scale change of wave frequency. In addition, in the prior art, the designed hydraulic device realizes the latching and releasing of the movement of the floater through a latching control strategy, and realizes the synchronization of the speed of the floater and the wave force. In the control method, in the prior art, Model Predictive Control (MPC) is applied to a wave energy power generation device, a controller capable of realizing maximum wave energy capture is designed, and a mathematical model adopted by the scheme can also consider that the actual conditions of sea conditions are closer to the actual control effect. The disturbance observation method is applied to the wave energy power generation device, and the size of the applied step length can be adjusted according to the increase and decrease of the power, so that the maximum power point is reached.
The tide effect compensation system does not consider the applicability problem of arranging the large-span wave frequency change of the sea area; compared with the change of wave frequency, the Archimedes direct-drive wave power generation device has the advantages that the air pressure change is slower, the Archimedes direct-drive wave power generation device is difficult to adapt to the change of large-span waves, and the structure is more complex; the latching control strategy depends on the length of time that the float latches, and the point in time for optimal release is not easily estimated accurately.
When the predictive control is applied to a wave energy power generation device, the dependence on a mathematical model is strong, the modeling error can influence the actual control effect, the kinematics of the PMLG (linear generator) is not taken into consideration, and the final control input is only at the level of the back electromagnetic force. The step length of the disturbance observation method applied to the wave energy power generation device is not easy to select, oscillation is easy to generate near the maximum power point when the step length is too large, and the arrival speed is too slow when the step length is too small, so that the dynamic performance of a system is influenced.
Disclosure of Invention
According to the technical problems provided by the invention, a direct drive type wave power generation maximum wave energy accurate tracking control method based on spring resonance assistance is provided. The invention is mainly used for improving the accurate tracking control of the maximum wave energy of direct-drive wave energy power generation, and designs a novel spring resonance auxiliary system mechanical device aiming at a direct-drive wave energy power generation Device (DWEC). A control model is established based on a mechanical auxiliary system and a linear generator (PMLG) dynamic model, and a hybrid finite time tracking control (SR-HFTC) strategy is provided on the basis. Firstly, aiming at the influence of a marine complex environment on a power generation process, a finite time disturbance observer (FDO) is adopted to quickly compensate environmental disturbance. Aiming at a motor control system, a d-axis current finite time regular and an FDO-based nonsingular terminal sliding mode (FDO-NTSM) q-axis current controller are respectively designed to accurately realize DWEC buoy and wave resonance in a complex environment and achieve maximum wave energy tracking. Simulation research and comprehensive comparison show that the proposed SR-HFTC strategy has obvious quick adaptability and accurate maximum wave energy tracking performance under the condition of disturbance and a spring resonance auxiliary system.
The technical means adopted by the invention are as follows:
a direct-drive wave energy power generation maximum wave energy accurate tracking control method based on spring resonance assistance comprises the following steps:
s1, constructing a mathematical model of the direct drive type wave energy power generation device;
s2, designing a mixed finite time tracking control strategy;
and S3, performing stability analysis on the designed mixed limited time tracking control strategy.
Further, the specific implementation method of step S1 is as follows:
assuming that the direct drive type wave energy power generation device always runs in the vertical direction, the permanent magnet and the coil generate relative motion under the driving of waves, and the wave mechanical energy is converted into electric energy, then the kinematic equation of the direct drive type wave energy power generation device is as follows:
wherein m represents the mass of the direct-drive wave power generation device, x represents the mover displacement of the linear generator in the vertical direction, and feRepresenting wave excitation force, fgRepresenting the back electromagnetic force of the linear generator,
Rgdenotes the internal damping of the linear generator, κ2Representing the elastic coefficient, f, of the linear generatoruRepresenting lumped unknowns including unmodeled dynamics, uncertainty, disturbance, viscous and frictional forces, fr and fbRepresenting the radiation force and the static buoyancy of the float respectively,
fb＝-κ1x+mg，madenotes an additional mass, RaDenotes external damping,. kappa1ρ gS represents a buoyancy coefficient, ρ represents a sea water density, g represents a gravitational acceleration, and S represents a contact surface of the float and the wave;
in order to change the natural frequency of the direct-drive wave power generation device and adapt to the wave frequency of the distributed sea area, a spring resonance auxiliary system is designed, the equivalent is a spring, and the expression is as follows:
fs＝κ3x
combining the kinematic equation of the direct drive type wave power generation device, the radiation force, the static buoyancy of the floater and the back electromagnetic force of the linear generator to obtain:
wherein M is M + MaThe total mass of the direct-drive wave power generation device is represented;
calculating the output power of the direct drive type wave energy power generation device as follows:
make output power P of direct drive type wave power generation devicegMaximum output, let Ra＝Rg，κ1＝-κ2By adjusting the spring constant k3＝ω2M realizes the maximum wave energy capture of the direct-drive wave energy power generation device;
a dynamic equation of the direct-drive wave power generation device is constructed as follows:
wherein ,id and iqCurrent components of the d and q axes, respectively;
the back electromagnetic force of the generator is expressed in the form:
wherein ,Ld and LqInductances of the d and q axes, respectively; from the above equation, the back electromagnetic force f can be changed by changing the current components of the d and q axesg；
And (3) taking a kinetic equation and a kinematic equation into consideration, and constructing a control model of the direct-drive wave energy power generation device:
wherein ,
further, the specific implementation method of step S2 is as follows:
s21, designing a finite time disturbance observer:
it is assumed that the unknown complex ocean disturbance d satisfies the condition of being continuously differentiable and bounded, i.e.
L represents a bounded normal number of bits,
the designed finite time disturbance observer is expressed as follows:
wherein ,vb、d and 
are respectively covered for a limited time
And
observed, sigα(x)＝|x|αsign (x) is a finite time transformation equation;
the following observation errors are defined:
the observation error dynamic equation is as follows:
by selecting a suitable parameter lambda1,λ2,λ3And L, tracking error μ1,μ2,μ3Is stabilized to zero for a limited time, and:
s22, designing a d-axis current finite time rule:
according to vector control, designing a d-axis sliding mode control surface as follows:
sd＝id+kidxe
wherein ,kid＞0，xe＝x-xdRepresenting the displacement error, xdRepresenting a reference displacement;
calculating the first derivative of the d-axis sliding-mode control surface as follows:
s23, designing a d-axis voltage control law:
ud＝Ls(-lsid+γ2viq+kidve+η1sign(sd))
wherein ,η10 is a designed normal number;
s24, designing a q-axis current tracking controller:
in conjunction with a q-axis current tracking system, the tracking error is defined as:
xe＝x-xd,ve＝v-vd
wherein ,vdRepresents a reference speed; obtaining:
the current control law of the q axis is designed by adopting a backstepping method, which comprises the following steps:
an error dynamic equation is obtained as follows:
wherein ,
designing a q-axis nonsingular terminal sliding mode surface as follows:
wherein beta is more than 0, and p/q is more than 1 and less than 2, which are designed normal numbers;
considering a q-axis current tracking system and a nonsingular terminal sliding mode surface, designing a q-axis voltage control law design as follows:
further, the specific implementation method of step S3 is as follows:
s31, assuming that a mixed finite time tracking control strategy meets the control model of the direct drive type wave energy power generation device, under the action of a disturbance observer and a control law, lumped unknown disturbance of the direct drive type wave energy power generation device is observed in finite time, and meanwhile, an error signal x is obtainede,ve,lqeStabilized to zero, actual state controllerTracking the upper expected value under action;
and S32, proving that the d-axis current converges on the sliding mode surface within a limited time, and the displacement, the speed tracking error and the q-axis current tracking error gradually and stably converge to zero after reaching the designed nonsingular terminal sliding mode surface.
Further, the specific implementation method of step S32 is as follows:
the first step is as follows: for the d-axis current tracking control subsystem, the following Lyapunov function was chosen:
derivation of the above equation yields:
substituting the voltage control law into the formula to obtain:
and (4) conclusion: the tracking error of the d-axis current tracking system converges to zero within a limited time;
the second step is that: for the q-axis current tracking system, the following Lyapunov function is established:
derivation of the above equation yields:
substituting the control law and the disturbance observation result into the formula to obtain:
the third step: considering a maximum wave energy tracking control system of the whole direct-drive wave energy power generation device, designing a Lyapunov function:
V＝Vd+Vq
combining a disturbance observer and a control law to obtain:
thus, V (x)e(0),ve(0) Is bounded, V (x)e(t),ve(t)) is a non-incrementally bounded function, then:
therefore, the temperature of the molten metal is controlled,
is always continuous and is ensured by selecting proper parameters
According to Lyapunov theory of stability and Barbalt's theorem, when t → ∞, xe and veAnd converging to zero, and gradually stabilizing the whole closed-loop direct-drive type wave energy power generation device under a mixed finite time tracking control strategy.
Compared with the prior art, the invention has the following advantages:
1. the invention designs a novel spring resonance auxiliary system mechanical device aiming at a direct drive wave power generation Device (DWEC). A control model is established based on a mechanical auxiliary system and a linear generator (PMLG) dynamic model, and resonance of the direct-drive wave power generation device in a regularly-changed sea area caused by monsoon is realized by designing a spring coaxial with a rotor.
2. The invention provides a direct-drive wave energy power generation maximum wave energy accurate tracking control method based on spring resonance assistance, which respectively uses a finite time regurator and a nonsingular terminal sliding mode controller (FDO-NTSM) based on disturbance observation to realize the tracking control of a closed-loop system. The problem of maximum wave energy tracking control of a direct-drive wave energy power generation Device (DWEC) in an arrangement sea area with interference is solved, and reference displacement and speed tracking is realized.
Based on the reason, the invention can be widely popularized in the fields of new energy application and the like.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a flow chart of the method of the present invention.
Fig. 2 is a schematic structural diagram of a direct-drive wave energy power generation device provided by the embodiment of the invention.
Fig. 3 is a comparison diagram of the speed and the wave excitation force phase of the direct-drive wave energy power generation device provided by the embodiment of the invention.
Fig. 4 is an observation result diagram of the disturbance applied to the direct-drive wave energy power generation device provided by the embodiment of the invention.
Fig. 5 is a diagram illustrating a result of tracking displacement and speed of the direct drive type wave power generation device and an error result according to the embodiment of the present invention.
Fig. 6 is a current tracking and tracking error result diagram of the direct-drive wave energy power generation device provided by the embodiment of the invention.
Detailed Description
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
As shown in fig. 1, the invention provides a spring resonance assistance-based direct-drive wave power generation maximum wave energy accurate tracking control method, which comprises the following steps:
s1, constructing a mathematical model of the direct drive type wave energy power generation device;
in specific implementation, as a preferred embodiment of the present invention, in this embodiment, as shown in fig. 2, the direct drive type wave energy power generation device is composed of four main parts, namely, a floater, a Permanent Magnet Linear Generator (PMLG), a spring resonance auxiliary system, and a back-end control circuit, wherein the floater is directly connected to a permanent magnet of the Permanent Magnet Linear Generator (PMLG), and the spring resonance auxiliary system is designed between a PLMG mover and a stator. Assuming that the direct drive type wave energy power generation device always runs in the vertical direction, the permanent magnet and the coil generate relative motion under the driving of waves, and the wave mechanical energy is converted into electric energy, then the kinematic equation of the direct drive type wave energy power generation device is as follows:
wherein m represents the mass of the direct-drive wave power generation device, x represents the mover displacement of the linear generator in the vertical direction, and feRepresenting wave excitation force, fgRepresenting the back electromagnetic force of the linear generator,
Rgdenotes the internal damping of the linear generator, κ2Representing the elastic coefficient, f, of the linear generatoruRepresenting lumped unknowns including unmodeled dynamics, uncertainty, disturbance, viscous and frictional forces, fr and fbRepresenting the radiation force and the static buoyancy of the float respectively,
fb＝-κ1x+mg，madenotes an additional mass, RaDenotes external damping,. kappa1ρ gS represents a buoyancy coefficient, ρ represents a sea water density, g represents a gravitational acceleration, and S represents a contact surface of the float and the wave;
in order to change the natural frequency of the direct-drive wave power generation device and adapt to the wave frequency of the distributed sea area, a spring resonance auxiliary system is designed, the equivalent is a spring, and the expression is as follows:
fs＝κ3x
combining the kinematic equation of the direct drive type wave power generation device, the radiation force, the static buoyancy of the floater and the back electromagnetic force of the linear generator to obtain:
wherein M is M + MaThe total mass of the direct-drive wave power generation device is represented;
calculating the output power of the direct drive type wave energy power generation device as follows:
make output power P of direct drive type wave power generation devicegMaximum output, let Ra＝Rg，κ1＝-κ2By adjusting the spring constant k3＝ω2M realizes the maximum wave energy capture of the direct-drive wave energy power generation device;
a dynamic equation of the direct-drive wave power generation device is constructed as follows:
wherein ,id and iqCurrent components of the d and q axes, respectively;
the back electromagnetic force of the generator is expressed in the form:
wherein ,Ld and LqInductances of the d and q axes, respectively; from the above equation, the back electromagnetic force f can be changed by changing the current components of the d and q axesg；
And (3) taking a kinetic equation and a kinematic equation into consideration, and constructing a control model of the direct-drive wave energy power generation device:
wherein ,
s2, designing a mixed finite time tracking control strategy;
in specific implementation, as a preferred embodiment of the present invention, the specific implementation method of step S2 is as follows:
s21, designing a finite time disturbance observer:
assuming unknown complex ocean perturbationsThe motion d being continuously differentiable and bounded, i.e.
L represents a bounded normal number of bits,
the designed finite time disturbance observer is expressed as follows:
wherein ,vb、d and 
are respectively covered for a limited time
And
observed, sigα(x)＝xαsign (x) is a finite time transformation equation;
the following observation errors are defined:
the observation error dynamic equation is as follows:
by selecting a suitable parameter lambda1,λ2,λ3And L, tracking error μ1,μ2,μ3Is stabilized to zero for a limited time, and:
s22, designing a d-axis current finite time rule:
according to vector control, designing a d-axis sliding mode control surface as follows:
sd＝id+kidxe
wherein ,kid＞0，xe＝x-xdRepresenting the displacement error, xdRepresenting a reference displacement;
calculating the first derivative of the d-axis sliding-mode control surface as follows:
s23, designing a d-axis voltage control law:
wherein ,η 10 is a designed normal number;
s24, designing a q-axis current tracking controller:
in conjunction with a q-axis current tracking system, the tracking error is defined as:
xe＝x-xd,ve＝v-vd
wherein ,vdRepresents a reference speed; obtaining:
the current control law of the q axis is designed by adopting a backstepping method, which comprises the following steps:
an error dynamic equation is obtained as follows:
wherein ,
designing a q-axis nonsingular terminal sliding mode surface as follows:
wherein beta is more than 0, and p/q is more than 1 and less than 2, which are designed normal numbers;
considering a q-axis current tracking system and a nonsingular terminal sliding mode surface, designing a q-axis voltage control law design as follows:
and S3, performing stability analysis on the designed mixed limited time tracking control strategy.
In specific implementation, as a preferred embodiment of the present invention, the specific implementation method of step S3 is as follows:
s31, assuming that a mixed finite time tracking control strategy meets the control model of the direct drive type wave energy power generation device, under the action of a disturbance observer and a control law, lumped unknown disturbance of the direct drive type wave energy power generation device is observed in finite time, and meanwhile, an error signal x is obtainede,ve,lqeStabilized to zero, and the upper expected value is tracked under the action of an actual state controller;
and S32, proving that the d-axis current converges on the sliding mode surface within a limited time, and the displacement, the speed tracking error and the q-axis current tracking error gradually and stably converge to zero after reaching the designed nonsingular terminal sliding mode surface.
The first step is as follows: for the d-axis current tracking control subsystem, the following Lyapunov function was chosen:
derivation of the above equation yields:
substituting the voltage control law into the formula to obtain:
and (4) conclusion: the tracking error of the d-axis current tracking system converges to zero within a limited time;
the second step is that: for the q-axis current tracking system, the following Lyapunov function is established:
derivation of the above equation yields:
substituting the control law and the disturbance observation result into the formula to obtain:
the third step: considering a maximum wave energy tracking control system of the whole direct-drive wave energy power generation device, designing a Lyapunov function:
V＝Vd+Vq
combining a disturbance observer and a control law to obtain:
thus, V (x)e(0),ve(0) Is bounded, V (x)e(t),ve(t)) is a non-incrementally bounded function, then:
therefore, the temperature of the molten metal is controlled,
is always continuous and is ensured by selecting proper parameters
According to Lyapunov theory of stability and Barbalt's theorem, when t → ∞, xe and veAnd converging to zero, and gradually stabilizing the whole closed-loop direct-drive type wave energy power generation device under a mixed finite time tracking control strategy.
Examples
The method of the invention is compared with a method combining an equivalent circuit method and Sliding Mode Control (SMC) to verify the effectiveness of the control model and the control scheme provided by the invention. The control scheme of the invention provides a high-order control model, and a traditional equivalent circuit method is adopted to obtain an ideal value i of q-axis currentq *And the control process is converted into a high-order model virtual control quantity to be directly controlled, so that the control accuracy of the device is improved. In this embodiment, the reference displacement of the direct drive wave power generation apparatus (DWEC) is as follows:
xd＝sin(0.2t+3)cos(0.5t+8)
the unknown disturbance is:
d＝20sin(2t/3+5)cos0.5tcos(t/3)/M
the parameters of the controller and observer are selected to be kid＝2，kiq＝3，η1＝0.1，η2＝0.2，p＝2，q＝3，l＝0.2，λ1＝5.6，λ2＝0.9，λ3＝1.8。
As can be seen from fig. 3, SR-HFTC (hybrid finite time tracking control strategy) can realize that the device mover speed is in phase with the wave excitation force, i.e. the mover and the wave can achieve resonance. Compared with SMC (sliding mode control), the method can realize more accurate tracking effect by considering the influence of unknown disturbance, and simultaneously proves the effectiveness of the control model and the control scheme provided by the invention.
Secondly, aiming at a SR-HFTC (hybrid finite time tracking control strategy) scheme provided by wave verification of large-span changes in sea areas, the reference displacement of the direct-drive wave power generation device is as follows:
xd＝2sintcos(0.5t)+cos(0.8t)cos(0.25t)
the parameter of the unknown disturbance, the controller and the disturbance observer is selected to be kid＝1.8，kiq＝2，η1＝0.3，η2＝0.09，p＝2，q＝3，l＝0.1，λ1＝9，λ2＝2，λ3＝2。
The simulation results are shown in fig. 4-6. As shown in fig. 4, a finite time disturbance observer (FDO) can accurately estimate the disturbance. As shown in fig. 5, for the periodic waves in the interference environment, the tracking effect of FDO-NTSM and SR-HFTC is significantly better than that of NTSM, especially 16 to 20 seconds, and the time of maximum interference, which illustrates that the disturbance observer used herein can achieve effective rejection of interference. SR-HFTC is better than FDO-NTSM in error control, and the spring resonance auxiliary system provided by the method is favorable for tracking regular waves in a monsoon environment. As shown in FIG. 6, DWEC under the SR-HFTC scheme can track the reference current more quickly and accurately. The simulation results are combined to show that the proposed SR-HFTC scheme can effectively realize the resonance of the DWEC system in the deployment sea area and track the maximum wave energy.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (5)
1. A direct-drive wave energy power generation maximum wave energy accurate tracking control method based on spring resonance assistance is characterized by comprising the following steps:
s1, constructing a mathematical model of the direct drive type wave energy power generation device;
s2, designing a mixed finite time tracking control strategy;
and S3, performing stability analysis on the designed mixed limited time tracking control strategy.
2. The spring resonance assistance-based direct-drive wave energy power generation maximum wave energy accurate tracking control method according to claim 1, characterized in that the specific implementation method of the step S1 is as follows:
assuming that the direct drive type wave energy power generation device always runs in the vertical direction, the permanent magnet and the coil generate relative motion under the driving of waves, and the wave mechanical energy is converted into electric energy, then the kinematic equation of the direct drive type wave energy power generation device is as follows:
wherein m represents the mass of the direct-drive wave power generation device, x represents the mover displacement of the linear generator in the vertical direction, and feRepresenting wave excitation force, fgRepresenting the back electromagnetic force of the linear generator,
Rgdenotes the internal damping of the linear generator, κ2Representing the elastic coefficient, f, of the linear generatoruRepresenting lumped unknowns including unmodeled dynamics, uncertainty, disturbance, viscous and frictional forces, fr and fbRepresenting radiation force and static state of float, respectivelyThe buoyancy force is generated by the buoyancy force,
fb＝-κ1x+mg，madenotes an additional mass, RaDenotes external damping,. kappa1ρ gS represents a buoyancy coefficient, ρ represents a sea water density, g represents a gravitational acceleration, and S represents a contact surface of the float and the wave;
in order to change the natural frequency of the direct-drive wave power generation device and adapt to the wave frequency of the distributed sea area, a spring resonance auxiliary system is designed, the equivalent is a spring, and the expression is as follows:
fs＝κ3x
combining the kinematic equation of the direct drive type wave power generation device, the radiation force, the static buoyancy of the floater and the back electromagnetic force of the linear generator to obtain:
wherein M is M + MaThe total mass of the direct-drive wave power generation device is represented;
calculating the output power of the direct drive type wave energy power generation device as follows:
make output power P of direct drive type wave power generation devicegMaximum output, let Ra＝Rg，κ1＝-κ2By adjusting the spring constant k3＝ω2M realizes the maximum wave energy capture of the direct-drive wave energy power generation device;
a dynamic equation of the direct-drive wave power generation device is constructed as follows:
wherein ,id and iqCurrent components of the d and q axes, respectively;
the back electromagnetic force of the generator is expressed in the form:
wherein ,Ld and LqInductances of the d and q axes, respectively; from the above equation, the back electromagnetic force f can be changed by changing the current components of the d and q axesg；
And (3) taking a kinetic equation and a kinematic equation into consideration, and constructing a control model of the direct-drive wave energy power generation device:
wherein ,
3. the spring resonance assistance-based direct-drive wave energy power generation maximum wave energy accurate tracking control method according to claim 1, characterized in that the specific implementation method of the step S2 is as follows:
s21, designing a finite time disturbance observer:
it is assumed that the unknown complex ocean disturbance d satisfies the condition of being continuously differentiable and bounded, i.e.
L represents a bounded normal number of bits,
the designed finite time disturbance observer is expressed as follows:
wherein ,vb、d and 
are respectively covered for a limited time
And
observed, sigα(x)＝|x|αsign (x) is a finite time transformation equation;
the following observation errors are defined:
the observation error dynamic equation is as follows:
by selecting a suitable parameter lambda1,λ2,λ3And L, tracking error μ1,μ2,μ3Is stabilized to zero for a limited time, and:
s22, designing a d-axis current finite time rule:
according to vector control, designing a d-axis sliding mode control surface as follows:
sd＝id+kidxe
wherein ,kid＞0，xe＝x-xdRepresentation positionError of shift, xdRepresenting a reference displacement;
calculating the first derivative of the d-axis sliding-mode control surface as follows:
s23, designing a d-axis voltage control law:
wherein ,η10 is a designed normal number;
s24, designing a q-axis current tracking controller:
in conjunction with a q-axis current tracking system, the tracking error is defined as:
xe＝x-xd,ve＝v-vd
wherein ,vdRepresents a reference speed; obtaining:
the current control law of the q axis is designed by adopting a backstepping method, which comprises the following steps:
an error dynamic equation is obtained as follows:
wherein ,
designing a q-axis nonsingular terminal sliding mode surface as follows:
wherein beta is more than 0, and p/q is more than 1 and less than 2, which are designed normal numbers;
considering a q-axis current tracking system and a nonsingular terminal sliding mode surface, designing a q-axis voltage control law design as follows:
4. the spring resonance assistance-based direct-drive wave energy power generation maximum wave energy accurate tracking control method according to claim 1, characterized in that the specific implementation method of the step S3 is as follows:
s31, assuming that a mixed finite time tracking control strategy meets the control model of the direct drive type wave energy power generation device, under the action of a disturbance observer and a control law, lumped unknown disturbance of the direct drive type wave energy power generation device is observed in finite time, and meanwhile, an error signal x is obtainede,ve,lqeStabilized to zero, and the upper expected value is tracked under the action of an actual state controller;
and S32, proving that the d-axis current converges on the sliding mode surface within a limited time, and the displacement, the speed tracking error and the q-axis current tracking error gradually and stably converge to zero after reaching the designed nonsingular terminal sliding mode surface.
5. The spring resonance assistance-based direct-drive wave energy power generation maximum wave energy accurate tracking control method according to claim 4, characterized in that the specific implementation method of the step S32 is as follows:
the first step is as follows: for the d-axis current tracking control subsystem, the following Lyapunov function was chosen:
derivation of the above equation yields:
substituting the voltage control law into the formula to obtain:
and (4) conclusion: the tracking error of the d-axis current tracking system converges to zero within a limited time;
the second step is that: for the q-axis current tracking system, the following Lyapunov function is established:
derivation of the above equation yields:
substituting the control law and the disturbance observation result into the formula to obtain:
the third step: considering a maximum wave energy tracking control system of the whole direct-drive wave energy power generation device, designing a Lyapunov function:
V＝Vd+Vq
combining a disturbance observer and a control law to obtain:
thus, V (x)e(0),ve(0) Is bounded, V (x)e(t),ve(t)) is a non-incrementally bounded function, then:
therefore, the temperature of the molten metal is controlled,
is always continuous and is ensured by selecting proper parameters
According to Lyapunov theory of stability and Barbalt's theorem, when t → ∞, xe and veAnd converging to zero, and gradually stabilizing the whole closed-loop direct-drive type wave energy power generation device under a mixed finite time tracking control strategy.
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