A built-in direct-drive wave energy power generation device maximum power extraction control method

Abstract

The application relates to the technical field of wave power generation, and discloses a maximum power extraction control method of an embedded direct-drive wave power generation device, which is applied to the embedded direct-drive wave power generation device and comprises the following steps: acquiring a motion position signal of a core power generation unit, a capacitor voltage signal of a generator rectifier output end and an inductance current signal of a boost conversion circuit; determining a position error signal between a motion reference position of the core power generation unit and a detected real-time position, and adjusting to obtain a position reference voltage; collecting the capacitor voltage and the inductance current of the generator rectifier output end in real time, determining an optimal reference voltage, and adjusting to obtain an MPPT reference voltage; determining a sum value between the position reference voltage and the MPPT reference voltage, and setting the sum value as a final capacitor reference voltage of a generator output end; and calculating a duty cycle D by using a PI controller, and generating a PWM signal to realize tracking control of the maximum power. The application improves the energy conversion efficiency of the embedded direct-drive wave power generation device.

Description

Technical Field

[0001] The present invention relates to the technical field of wave energy power generation, and in particular to a maximum power extraction control method for a built-in direct-drive wave energy power generation device. Background Art

[0002] The ocean data buoy wave energy power generation device combines wave energy collection and data monitoring technology. The wave energy power generation device converts the mechanical energy generated by wave motion into electrical energy to power the sensors and communication equipment on the buoy. Its key technologies include wave energy converters, energy storage systems, and data transmission modules. With the increasing demand for renewable energy, this device can not only provide continuous power to remote sea areas, but also collect marine environmental data in real time, assist scientific research and ocean management, and become an important part of sustainable development. Among them, the built-in direct-drive wave power generation device designed and developed is installed inside the buoy, and uses the swaying of the buoy to generate electricity, which has good development prospects. However, the control method for the maximum power extraction of the built-in direct-drive wave power generation device has not been perfected. The present invention aims to solve the maximum power extraction control method of the built-in direct-drive wave power generation device and improve its energy conversion efficiency.

[0003] Chinese Patent Publication No. CN111271214B discloses a wave energy power generation device comprising: a bracket fixed within a buoy compartment; a motor platform disposed within the bracket and capable of linear motion relative to the bracket; a magnetic screw stator rod extending through the motor platform and secured to the bracket at both ends; a magnetic screw rotor barrel connected to the motor platform via a rotating structure and concentrically sleeved around the magnetic screw stator rod; and a generator connected to the magnetic screw rotor barrel. Chinese Patent Publication No. CN118188280A also discloses a built-in swaying buoy wave energy power generation system and control method. The active motion control method utilizes dynamic load control to increase the operational weight of the core power generation unit and improve the operating efficiency of the magnetic screw during the control process, thereby avoiding magnetic slippage associated with the heavy core power generation unit. However, the active motion control method still fails to address the maximum power extraction issue of built-in direct-drive wave power generation devices. Addressing this issue could effectively improve the power generation efficiency and thus the power generation capacity of built-in direct-drive wave power generation devices. Summary of the Invention

[0004] The purpose of the present invention is to provide a maximum power extraction control method for a built-in direct-drive wave energy power generation device, aiming to solve the above-mentioned problems, achieve maximum power extraction of the built-in direct-drive wave energy power generation device, and thus improve the energy conversion efficiency of the built-in direct-drive wave energy power generation device.

[0005] The present invention provides a maximum power extraction control method for a built-in direct-drive wave energy power generation device, which is applied to the built-in direct-drive wave energy power generation device. The power generation device includes a rocking buoy, a bracket, a guide rail, a core power generation unit, and a control system. The guide rail includes a magnetic screw and a positioning guide rail; the core power generation unit includes a magnetic screw rotor and a link mechanism, and a generator; the control system includes a position sensor, a power electronic circuit, a DSP controller, and an RC load.

[0006] The control method includes:

[0007] Real-time acquisition of the motion position signal of the core power generation unit, the capacitor voltage signal of the generator rectifier output end, and the inductor current signal of the boost conversion circuit;

[0008] Determine the motion reference position X of the core power generation unit ref The position error signal between the real-time position X detected by the position sensor is adjusted using a PI controller to obtain the position reference voltage U pos_ref ;

[0009] The capacitor voltage U at the generator rectifier output end is collected in real time through the DSP controller dc and the inductor current I dc , the optimal reference voltage U is obtained by hill climbing method MPPT , and use the PI controller to adjust the MPPT reference voltage U MPPT_ref ;

[0010] Determine the position reference voltage U pos_ref and MPPT reference voltage U MPPT_ref The sum value is set as the final capacitor reference voltage U at the generator output end. dc_ref ;

[0011] The PI controller is used to calculate the duty cycle D and generate a PWM signal to track the capacitor voltage at the generator rectifier output end.

[0012] Preferably, the generator is a permanent magnet synchronous generator.

[0013] Preferably, the bracket is fixedly installed in the swing buoy, the core power generation unit is arranged on the guide rail, and the permanent magnet synchronous generator is connected to the core power generation unit.

[0014] Preferably, constructing an equivalent circuit model for the power generation device includes:

[0015] The mathematical model of the core power generation unit is constructed as shown in formula (1);

[0016]

[0017] Where m is the mass of the core power generation unit, θ M is the tilt angle of the buoy, ω is the frequency of the buoy's oscillation, is the initial phase of the buoy's swing, F M The no-load magnetic resistance of the core power generation unit includes friction resistance and minimum driving torque, F T The additional magnetic resistance is the resistance transmitted to the core power generation unit by the permanent magnet synchronous generator through the load, a is the acceleration of the core power generation unit on the guide rail, and x is the displacement of the core power generation unit on the guide rail;

[0018] The mathematical model of the transmission process of the magnetic screw is constructed as shown in formula (2):

[0019]

[0020] Among them, ω PMSG is the angular velocity of the permanent magnet synchronous generator rotor shaft, θ PMSG is the rotation angle of the rotor shaft of the permanent magnet synchronous generator, ω r is the rotational angular velocity of the driven wheel of the chain drive, R is the radius of the chain drive driving wheel, r is the radius of the chain drive driven wheel, and λ is the pole pitch of the magnetic screw;

[0021] The mathematical model of the torque of the permanent magnet synchronous generator is constructed as follows:

[0022]

[0023] Among them, T PMSG is the torque of the permanent magnet synchronous generator, T e is the electromagnetic torque of the permanent magnet synchronous generator, J is the inertia moment of the permanent magnet synchronous generator, and B is the rotational damping coefficient of the rotor shaft;

[0024] According to equations (1), (2) and (3), the equivalent circuit model of the power generation device is obtained;

[0025] Analyzing the equivalent circuit model, we can obtain formula (4):

[0026]

[0027] in, o > is the average current value in half a cycle of the equivalent circuit, P n is the number of pole pairs of the permanent magnet synchronous generator, ψ f is the stator flux of the permanent magnet synchronous generator, γ is a moment in the half cycle of the buoy swing, T is the period of the buoy swing, U s is the phase voltage of the permanent magnet synchronous generator;

[0028] According to formula (4), we can get formula (5); ​

[0029]

[0030] wherein, <P o > is the average output power on the load resistance in the half cycle of the equivalent circuit, u o > is the average output voltage on the load resistance.

[0031] Compared with the prior art, the beneficial effects of the present application are that the present application is a maximum power control system developed based on the built-in direct-drive wave power generation device, which fills the gap of the maximum power control system in this field. For the built-in direct-drive wave power generation device with periodic changes in input power and zero input power, the P-V curve of output power is calculated by the equivalent circuit, and the maximum power control of the built-in direct-drive wave power generation device is realized by the proposed maximum power tracking technology. This method improves the energy conversion efficiency of the built-in direct-drive wave power generation device. In addition, the system can flexibly adapt to different wave conditions, ensuring stable output power in various environments, and improving the flexibility and economy of energy utilization.

[0032] An equivalent circuit model of a new built-in direct-drive wave power generation device is established. The kinematic model of the built-in direct-drive wave power generation device is equivalent to the output power electronic circuit of the load end permanent magnet synchronous motor, and the full equivalent mathematical model from input to output is established by combining the two, and the average power at the output end of the permanent magnet synchronous motor is solved. The relationship between the average output power in the half cycle wave and the output voltage of the permanent magnet synchronous motor is obtained, and the corresponding P-V curve is obtained, and the control parameters of the maximum power tracking control of the built-in direct-drive wave power generation device are obtained.

[0033] The power generation efficiency of the built-in direct-drive wave power generation device is improved. Through the calculation and modeling of the mathematical model, the output voltage value of the permanent magnet synchronous motor corresponding to the maximum power of the built-in direct-drive wave power generation device is obtained, and then the voltage at the output end of the permanent magnet synchronous motor is stabilized at the voltage corresponding to the maximum power point found by the hill climbing method through the control of the control system, so that the maximum power extraction of the built-in direct-drive wave power generation device can be realized. This maximum power control method can improve the power generation efficiency of the built-in direct-drive wave power generation device. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor on the basis of the provided drawings.

[0035] Figure 1It is a flow chart of a maximum power extraction control method of a built-in direct-drive wave energy power generation device according to the present invention.

[0036] Figure 2 This is an equivalent circuit diagram of a built-in direct-drive wave energy power generation device of the present invention.

[0037] Figure 3 This is a diagram of a maximum power extraction control method for a built-in direct-drive wave energy power generation device according to the present invention.

[0038] Figure 4 It is a PV curve obtained by fitting the PV curve obtained by the equivalent circuit of the built-in direct-drive wave energy power generation device provided by the embodiment of the present invention and the PV data points obtained by the joint simulation model.

[0039] Figure 5 This is a diagram of the voltage across the load and a reference voltage signal when the maximum power extraction method is applied, as provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0041] The present invention provides a maximum power control method for a built-in direct-drive wave power generation device. This method is used to achieve maximum power extraction from the built-in direct-drive wave power generation device, thereby improving the energy conversion efficiency of the built-in direct-drive wave power generation device. To achieve this objective, the present invention is based on the inventor's previously published Chinese patent publication No. CN111271214B, which discloses a wave energy power generation device, and the inventor's previously published Chinese patent publication No. CN118188280A, which discloses a built-in swaying buoy wave energy power generation system. The wave power generation device comprises: a bracket fixed to the internal compartment of the buoy; a fixed guide rod and both ends of a magnetic screw stator rod fixed to the bracket; a core power generation unit, coupled to the stator rod by a magnetic screw rotor barrel, capable of left and right movement along the magnetic screw stator rod; and a permanent magnet synchronous generator mounted on the core power generation unit and connected to the rotor barrel of the core power generation unit via a chain sprocket. The wave power generation device control system comprises: a position sensor; a permanent magnet synchronous motor output power electronics circuit; and a DSP control unit.

[0042] like Figure 1-Figure 3 As shown, the present invention provides a maximum power extraction control method for a built-in direct-drive wave energy power generation device, comprising:

[0043] The motion position signal of the core power generation unit, the capacitor voltage signal of the generator rectifier output end and the inductor current signal of the boost conversion circuit are acquired in real time.

[0044] Determine the motion reference position X of the core power generation unit ref The position error signal between the real-time position X detected by the position sensor is adjusted using a PI controller to obtain the position reference voltage U pos_ref .

[0045] The capacitor voltage U at the generator rectifier output is collected in real time by the DSP controller. dc and the inductor current I dc , the optimal reference voltage U is obtained by hill climbing method MPPT , and use the PI controller to adjust the MPPT reference voltage U MPPT_ref .

[0046] Determine the position reference voltage U pos_ref and MPPT reference voltage U MPPT_ref The sum value is set as the final capacitor reference voltage U at the generator output end. dc_ref .

[0047] The PI controller is used to calculate the duty cycle D and generate a PWM signal to track the capacitor voltage at the generator rectifier output end.

[0048] To further illustrate the present invention, the technical solution of the present invention is now described in detail:

[0049] The technical solution of the present invention is to propose a maximum power control strategy for a built-in direct-drive wave power generation device. The strategy comprises: 1. A position feedback control unit; a position sensor is used to measure the position of the core power generation unit on the guide rail in real time; the real-time position information can be used to determine the position of the core power generation unit, and position protection control of the core power generation unit is achieved by sampling, analyzing, and calculating this position information. 2. A digital control unit; by sampling the voltage at the rectifier output of the permanent magnet synchronous generator and the inductor voltage of the boost converter, the output power is optimized using a hill climbing method to find the capacitor voltage at the rectifier output corresponding to the maximum output power. A DSP controller generates a corresponding PWM wave to control the power electronic circuit to achieve load impedance control.

[0050] Kinematic modeling of the core power generation unit sliding down the slope:

[0051]

[0052] Where m is the mass of the core power generation unit, θ Mis the tilt angle of the buoy, ω is the frequency of the buoy's oscillation, is the initial phase of the buoy's swing, F M The no-load magnetic resistance of the core power generation unit includes friction resistance and minimum driving torque, F T The additional magnetic resistance is the resistance transmitted to the core power generation unit by the permanent magnet synchronous generator through the load, a is the acceleration of the core power generation unit on the guide rail, and x is the displacement of the core power generation unit on the guide rail.

[0053] make Assume there is Through KCL modeling transformation, we can get:

[0054]

[0055] Transmission performance is another important performance indicator of the magnetic screw. Its transmission ratio relationship with the pulley can be expressed as:

[0056]

[0057] Where Tm is the torque generated by MLS, λ is the lead of MLS, ω R is the angular velocity of the MLS rotor, ω r is the angular velocity of the PMSG rotor, R is the radius of the large gear of the pulley, r is the radius of the small gear of the pulley, and v is the moving speed of the MLS along the guide rail, which is also the moving speed of the CPGU.

[0058] For buoy power supply, it is necessary to select a permanent magnet synchronous generator (PMSG) with high efficiency and wear resistance. The mechanical torque of PMSG is expressed as:

[0059]

[0060] Among them, ω r is the input mechanical angular velocity on the PMSG shaft, J is the moment of inertia of the PMSG rotor, and B r is the viscosity coefficient on the PMSG rotor shaft, T e is the electromagnetic torque of PMSG, T m It is the input torque on the PMSG rotor shaft, that is, the driving torque generated on the rotor shaft by the magnetic resistance transmitted by the core power generation unit through the magnetic screw.

[0061] According to the vector control principle of PMSG generator, the relationship between PMSG electromagnetic torque Te, phase voltage Us and phase current Is can be expressed as:

[0062]

[0063] Since the built-in direct-drive WEC device belongs to small wave power generation device, the PMSG belongs to small generator, so the winding inductance L of the generator is very small and can be ignored, and the output voltage of the PMSG can be rewritten by integrating the above formula: d,q

[0064]

[0065] The above formula is integrated and equivalent according to the KCL law, and the equivalent circuit of the built-in direct-drive wave power generation device can be drawn through simple circuit processing.

[0066] The output power of the permanent magnet synchronous generator is analyzed, that is, the power on the load resistor ZOUT in the equivalent circuit is analyzed and solved:

[0067] Assuming that the swing of the buoy is sinusoidal, the current on the capacitor m can be represented as:

[0068] i m = mgα (t) - F M -F T (t);

[0069] Taking the half-cycle average value of the output sine wave for calculation can obtain the average output power across the output resistor:

[0070]

[0071] As described above, the output average power <P o > and U s are in a parabolic relationship. When the frequency of the buoy swing under the regular wave and the mass of the CPGU are constant, there is only one output phase voltage U s that can make the average output power of the CPGU in the half cycle maximum.

[0072] By controlling the end voltage of the permanent magnet synchronous generator rectifier output end by the DSP , the maximum power extraction control strategy of the built-in direct-drive wave power generation device can be realized.

[0073] Real-time acquisition of the motion position signal of the core power generation unit, the capacitor voltage signal of the generator rectifier output end and the inductor current signal of the boost conversion circuit; determine the position error signal between the motion reference position X ref of the core power generation unit and the real-time position X detected by the position sensor, and adjust the position reference voltage U pos_ref using the PI controller; the capacitor voltage U dc and the inductor current I dc of the generator rectifier output end are collected in real time by the DSP controller, and the optimal reference voltage U​MPPT , and use the PI controller to adjust the MPPT reference voltage U MPPT_ref ; Determine the position reference voltage U pos_ref and MPPT reference voltage U MPPT_ref The sum value is set as the final capacitor reference voltage U at the generator output end. dc_ref The duty cycle D is calculated using the PI control algorithm of the voltage loop. This is then applied to the power electronic converter circuit to track the capacitor voltage at the generator rectifier output.

[0074] Figure 4 This is a PV curve obtained by polynomial fitting of the PV data points obtained by the co-simulation model and the equivalent circuit PV curve of the built-in direct-drive wave power generation device provided by an embodiment of the present invention. The actual PV curve of the 90kg core power generation unit is calculated based on the relationship between the average power calculated from the equivalent circuit of the built-in direct-drive wave power generation device and the capacitor voltage at the PMSG rectifier output. The co-simulation model then plots the average output power of the PMSG of the 90kg core power generation unit at different voltages and performs a polynomial fit to ultimately obtain the PV curve of the built-in direct-drive wave power generation device.

[0075] Figure 5 The voltage across the load and the reference voltage signal under the maximum power extraction method provided by an embodiment of the present invention were simulated using a 90kg core power generation unit using the established co-simulation model. The reference voltage of the PMSG output capacitor voltage under the maximum power extraction control method was consistent with the corresponding reference voltage on the PV curve. These results demonstrate that the maximum power extraction control method can achieve maximum power extraction for a built-in direct-drive wave power generation device.

[0076] The maximum power extraction control method achieves a 32.7% efficiency in converting the gravitational potential energy of the 90kg core power generation unit into electrical energy. The algorithm stabilizes the capacitor voltage at the PMSG rectifier output at the voltage corresponding to the maximum power point, achieving maximum power extraction from the built-in direct-drive wave generator.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

[0078] The system provided in the above embodiment is only illustrated by the division of the above functional modules. In actual applications, the above functions can be assigned to different functional modules as needed, that is, the modules or steps in the embodiments of the present invention can be further decomposed or combined. For example, the modules in the above embodiment can be combined into one module or further divided into multiple sub-modules to complete all or part of the functions described above. The names of the modules and steps involved in the embodiments of the present invention are only for distinguishing the modules or steps and are not to be regarded as improper limitations of the present invention.

[0079] Those skilled in the art should be able to appreciate that, in conjunction with the modules and method steps of each example described in the embodiments disclosed herein, it is possible to implement them with electronic hardware, computer software, or a combination of the two, and the programs corresponding to the software modules and method steps can be placed in random access memory (RAM), internal memory, read-only memory (ROM), electrically erasable programmable ROM, registers, hard disks, removable disks, CD-ROMs, or any other form of storage medium known in the art. In order to clearly illustrate the interchangeability of electronic hardware and software, the composition and steps of each example have been generally described in terms of function in the above description. Whether these functions are performed in electronic hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present invention.

Claims

1. A method for controlling maximum power extraction of a built-in direct-drive wave energy power generation device, characterized in that: Applicable to a built-in direct-drive wave energy power generation device, the power generation device includes a swing buoy, a bracket, a guide rail, a core power generation unit and a control system. The guide rail includes a magnetic screw and a positioning guide rail; the core power generation unit includes a magnetic screw rotor and a link mechanism, and a generator; the control system includes a position sensor, a power electronic circuit, a DSP controller and an RC load; The method comprises: Real-time acquisition of the motion position signal of the core power generation unit, the capacitor voltage signal of the generator rectifier output end, and the inductor current signal of the boost conversion circuit; Determine a position error signal between a motion reference position of the core power generation unit and a real-time position detected by a position sensor, and adjust the position reference voltage using a PI controller; The capacitor voltage and inductor current at the generator rectifier output are collected in real time through the DSP controller, the optimal reference voltage is obtained through the hill climbing method, and the MPPT reference voltage is adjusted using the PI controller; Determine the sum of the position reference voltage and the MPPT reference voltage, and set the sum as the final capacitor reference voltage at the generator output; The PI controller is used to calculate the duty cycle D and generate a PWM signal to track the capacitor voltage at the generator rectifier output end.

2. The maximum power extraction control method of the built-in direct-drive wave energy power generation device according to claim 1 is characterized in that: The generator is a permanent magnet synchronous generator.

3. The maximum power extraction control method of the built-in direct-drive wave energy power generation device according to claim 2, characterized in that: The bracket is fixedly installed in the swing buoy, the core power generation unit is arranged on the guide rail, and the permanent magnet synchronous generator is connected to the core power generation unit.

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