Maximum power extraction control method for built-in direct-drive type wave power generation device

Abstract

The invention relates to the technical field of wave power generation, and discloses a maximum power extraction control method for a built-in direct-drive type wave power generation device, which is applied to the built-in direct-drive type wave power generation device. The method comprises the following steps: acquiring a motion position signal of a core power generation unit, a capacitor voltage signal of a generator rectification output end and an inductive current signal of a boost conversion circuit; determining a position error signal between the motion reference position of the core power generation unit and the detected real-time position, and adjusting to obtain a position reference voltage; capacitance voltage and inductance current of the rectification output end of the generator are collected in real time, optimal reference voltage is determined, and MPPT reference voltage is obtained through adjustment; determining the sum value between the position reference voltage and the MPPT reference voltage, and setting the sum value as the final capacitance reference voltage of the output end of the generator; and calculating a duty ratio D by using a PI controller, and generating a PWM signal to realize tracking control of the maximum power. The energy conversion efficiency of the built-in direct-drive type wave power generation device is improved.

Description

Technical Field

[0001] The 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 electricity for remote waters, but also collect marine environmental data in real time, assist scientific research and marine 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 it uses the swaying of the buoy to generate electricity, which has a good development prospect. 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 number CN111271214B discloses a wave energy power generation device, including: a bracket, fixed in a buoy cabin; a motor platform, arranged in the bracket and moving linearly relative to the bracket; a magnetic screw stator rod, passing through the motor platform, and fixed on the bracket at both ends; a magnetic screw mover barrel, connected to the motor platform through a rotating structure, and concentrically sleeved outside the magnetic screw stator rod; a generator, connected to the magnetic screw mover barrel. At the same time, Chinese patent publication number CN118188280A discloses a built-in swaying buoy wave energy power generation system and control method. The active motion control method adopts a dynamic load control method to increase the operable weight of the core power generation unit and achieves the purpose of improving the operating efficiency of the magnetic screw during the control process, thereby avoiding the magnetic slip phenomenon generated by the high-weight core power generation unit. However, the active motion control method still fails to solve the maximum power extraction problem of the built-in direct-drive wave power generation device. Solving this problem can effectively improve the power generation efficiency of the built-in direct-drive wave power generation device and thus increase its power generation. 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 power generation device, aiming to solve the above-mentioned problem, realize the maximum power extraction of 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.

[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 a built-in direct-drive wave energy power generation device, wherein the power generation device comprises a swing buoy, a bracket, a guide rail, a core power generation unit and a control system, wherein the guide rail comprises a magnetic screw and a positioning guide rail; the core power generation unit comprises a magnetic screw rotor and a link mechanism, and a generator; the control system comprises a position sensor, a power electronic circuit, a DSP controller and an RC load;

[0006] The control method comprises:

[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 by 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 rectifier output end of the generator.

[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 inclination angle of the swing buoy, ω is the frequency of the buoy swing, is the initial phase of the buoy 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 rotational 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 driving wheel of the chain drive, r is the radius of the driven wheel of the chain drive, 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 shown in formula (3):

[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 rotation damping coefficient of the rotor shaft;

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

[0025] The equivalent circuit model is analyzed to obtain equation (4):

[0026]

[0027] in, o > is the average current value in the half 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 certain 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] in, <P o > is the average output power on the load resistor within half a cycle of the equivalent circuit, u o > is the average output voltage across the load resistor.

[0031] Compared with the prior art, the beneficial effect of the present invention is that the present invention is a maximum power control system developed based on a built-in direct-drive wave power generation device, which fills the gap in the maximum public control system in this field. For a built-in direct-drive wave power generation device, which is a power generation device with periodic input power and zero input power, the PV curve of the output power is calculated using an equivalent circuit, and the maximum power control of the built-in direct-drive wave power generation device is achieved through 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, ensure stable output power in various environments, and improve the flexibility and economy of energy utilization.

[0032] Establish an equivalent circuit model for a new type of built-in direct-drive wave power generation device. Equivalently combine the kinematic model of the built-in direct-drive wave power generation device with the circuit model and the output power electronic circuit of the permanent magnet synchronous motor at the load end to establish a fully equivalent mathematical model from input to output, and solve the average power at the output end of the permanent magnet synchronous motor. Obtain the relationship between the average output power and the output voltage of the permanent magnet synchronous motor in the half-cycle wave and the corresponding PV curve, and obtain the control parameters of the maximum power tracking control of the built-in direct-drive wave power generation device.

[0033] Improve the power generation efficiency of the built-in direct-drive wave power generation device. 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 through the calculation and modeling of the mathematical model. Then, through the control of the control system, 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, so that the maximum power extraction of the built-in direct-drive wave power generation device can be achieved. This maximum power control method can improve the power generation efficiency of the built-in direct-drive wave power generation device. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[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 of the present invention.

[0036] Figure 2 It 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 of 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 It is a diagram of the voltage across the load and a reference voltage signal provided by an embodiment of the present invention when the maximum power extraction method is applied. DETAILED DESCRIPTION

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

[0041] The present invention provides a maximum power control method based on a built-in direct-drive wave power generation device. It is used to realize the maximum power extraction of the built-in direct-drive wave power generation, thereby improving the energy conversion efficiency of the built-in direct-drive wave power generation device. To achieve the above purpose, the present invention is based on a wave energy power generation device published by the inventor in China Patent Publication No. CN111271214B and a built-in swaying buoy wave energy power generation system published by the inventor in CN118188280A, and designs a maximum power control strategy for the built-in direct-drive wave power generation device. The wave power generation device includes: a bracket fixed to the internal cabin of the float; a fixed guide rod and a magnetic screw stator rod are fixed on the bracket at both ends; a core power generation unit, which can move left and right along the magnetic screw stator rod through the coupling of the magnetic screw rotor barrel and the stator rod; a permanent magnet synchronous generator is installed on the core power generation unit and connected to the rotor barrel of the core power generation unit through a chain sprocket. The control system of the wave power generation device includes: a position sensor; a permanent magnet synchronous motor output power electronic 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 by a PI controller to obtain the position reference voltage U pos_ref .

[0045] 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 .

[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 rectifier output end of the generator.

[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. It includes: 1. Position feedback control unit; the position sensor is used to measure the position of the core power generation unit on the guide rail in real time; the position of the core power generation unit can be determined by real-time position information, and the position information is sampled, analyzed and calculated to achieve position protection control of the core power generation unit. 2. Digital control unit; by sampling the voltage at the rectifier output end of the permanent magnet synchronous generator and sampling the inductor voltage of the boost converter, the output power is optimized using the hill climbing method to find the capacitor voltage at the rectifier output end corresponding to the maximum output power. The corresponding PWM wave is generated by calculation by the DSP controller to control the power electronic circuit to achieve control of the load impedance.

[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 inclination angle of the swing buoy, ω is the frequency of the buoy swing, is the initial phase of the buoy 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 that 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 PMSG mechanical torque expression is:

[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 is a small wave power generation device and the PMSG used is a small generator, it is assumed that the winding inductance L of the generator is d,q It is very small and can be ignored. By integrating the above relationship, the output voltage of PMSG can be rewritten as:

[0064]

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

[0066] Analyzing the output power of the permanent magnet synchronous generator output terminal is to analyze and solve the power on the load resistance ZOUT in the equivalent circuit:

[0067] Assuming that the swing of the buoy is sinusoidal, the current on the capacitor m can be expressed 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, the average output power across the output resistor can be obtained as:

[0070]

[0071] As mentioned above, it represents the average output power <P o >with U s There is a parabolic relationship between them. When the frequency of the buoy swing under regular waves and the mass of the CPGU are constant, there is a unique output phase voltage U s This maximizes the average output power of the CPGU within a half cycle.

[0072] The terminal voltage of the rectifier output end of the permanent magnet synchronous generator controlled by DSP is The maximum power extraction control strategy for 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 terminal and the inductor current signal of the boost conversion circuit; determining 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 by a PI controller to obtain the position reference voltage U pos_ref ; The capacitor voltage U at the rectifier output end of the generator 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 methodMPPT , 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. Finally, it is applied to the power electronic converter circuit to track the capacitor voltage at the rectifier output end of the generator.

[0074] Figure 4 It is the PV curve of the equivalent circuit of the built-in direct-drive wave power generation device provided by the embodiment of the present invention and the PV curve after polynomial fitting of the PV data points obtained by the joint simulation model; the actual PV curve of the 90kg core power generation unit is calculated according to the relationship between the average power calculated by the equivalent circuit of the built-in direct-drive wave power generation device and the capacitor voltage at the PMSG rectifier output end. Then, the average output electric power of the PMSG of the 90kg core power generation unit at different voltages is plotted and polynomially fitted by the joint simulation model, and finally the PV curve of the built-in direct-drive wave power generation device is obtained.

[0075] Figure 5 The voltage at both ends of the load and the reference voltage signal under the action of the maximum power extraction method provided by the embodiment of the present invention are: a simulation test is performed on a 90kg core power generation unit on the established joint simulation model. The reference voltage of the capacitor voltage at the output end of the PMSG under the maximum power extraction control method is consistent with the corresponding reference voltage on the PV curve. The results show that the maximum power extraction control method can achieve the maximum power extraction of the built-in direct-drive wave power generation device.

[0076] Under the maximum power extraction control method, the energy conversion efficiency of the 90kg core power generation unit from gravitational potential energy to electrical energy reaches 32.7%. The capacitor voltage at the PMSG rectifier output end is stabilized at the voltage corresponding to the maximum power point through the algorithm, realizing the maximum power extraction of the built-in direct-drive wave power generation device by the maximum power extraction control method.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. 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 solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

[0078] The system provided in the above embodiment is only illustrated by the division of the above functional modules. In practical 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 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 regarded as improper limitations of the present invention.

[0079] Those skilled in the art should be able to appreciate that the modules and method steps of each example described in conjunction with the embodiments disclosed herein can be implemented 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 technical field. In order to clearly illustrate the interchangeability of electronic hardware and software, the composition and steps of each example have been generally described in the above description according to the function. 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 maximum power extraction control method for a built-in direct-drive wave energy power generation device, characterized in that: Applied 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 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 by a PI controller to obtain the position reference voltage U pos_ref ; 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 ; 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 PI controller is used to calculate the duty cycle D and generate a PWM signal to track the capacitor voltage at the rectifier output end of the generator.

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 is 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.

4. The maximum power extraction control method of the built-in direct-drive wave energy power generation device according to claim 3 is characterized in that: Constructing an equivalent circuit model for the power generation device, including: The mathematical model of the core power generation unit is constructed as shown in formula (1); Where m is the mass of the core power generation unit, θ M is the inclination angle of the swing buoy, ω is the frequency of the buoy swing, is the initial phase of the buoy 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; The mathematical model of the transmission process of the magnetic screw is constructed as shown in formula (2): Among them, ω PMSG is the rotational 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 driving wheel of the chain drive, r is the radius of the driven wheel of the chain drive, and λ is the pole pitch of the magnetic screw; The mathematical model of the torque of the permanent magnet synchronous generator is constructed as shown in formula (3): 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 rotation damping coefficient of the rotor shaft; According to equations (1), (2) and (3), an equivalent circuit model of the power generation device is obtained; The equivalent circuit model is analyzed to obtain equation (4): in, o > is the average current value in the half 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 certain 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;​ According to formula (4), we can get formula (5); in, <P o > is the average output power on the load resistor within half a cycle of the equivalent circuit, u o > is the average output voltage across the load resistor.

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