A constant speed and pressure control method for hydraulic PTO of wave energy generation based on dual parameter joint regulation

Abstract

The present invention provides a wave energy power generation hydraulic PTO constant speed and pressure control method based on dual parameter joint adjustment, the method comprising: collecting the system oil pressure signal p of the main oil circuit through a pressure transmitter, and sending the oil pressure signal p to the oil pressure closed loop regulation module; measuring the torque signal M of the input shaft of the three-phase permanent magnet synchronous generator through a speed torque meter; g and speed signal n, and the signal M g and n are sent to the oil pressure open-loop regulation module, and the signal n is sent to the oil pressure closed-loop regulation module; the electromagnetic torque of the three-phase permanent magnet synchronous generator is controlled by the three-phase PWM rectifier to indirectly adjust the speed n; the three-phase current signal i at the outlet of the three-phase permanent magnet synchronous generator is collected by the generator vector controller a i b i c , and output SVPWM signal to the three-phase PWM rectifier, while receiving the speed signal n and setting speed n r The present invention has good speed stabilization and pressure stabilization effects.

Description

Technical Field

[0001] The present invention belongs to the field of wave energy power generation, and in particular relates to a wave energy power generation hydraulic PTO constant speed and pressure control method based on dual-parameter joint regulation. Background Art

[0002] Constant-pressure hydraulic PTO (CPHPTO) is a common transmission method used in wave energy generation devices. CPHPTO incorporates a high-pressure accumulator between the hydraulic cylinder and the motor, significantly reducing fluctuations in internal oil pressure, flow rate, and motor speed, thereby improving energy conversion efficiency. However, a disadvantage of CPHPTO is that it is difficult to rapidly adjust PTO force (torque) by varying motor displacement. Currently, CPHPTO is widely used in sea snake, Wavestar, raft, heave float, and various pendulum-type devices, including SEAREV, Eagle, buoyant pendulum, floating pendulum, and resonant devices.

[0003] Although the CPHPTO boasts high energy conversion efficiency and a relatively stable operating point, its internal nonlinear energy losses cannot be ignored. Furthermore, under complex, irregular sea conditions and the limited nominal capacity of the high-pressure accumulator, the system's operating point can still experience significant fluctuations. Therefore, it is necessary to comprehensively examine all possible operating points and, through operational control, ensure that the CPHPTO operates within a high-efficiency and stable range, avoiding excessive transmission losses and drastic fluctuations in operating parameters.

[0004] The paper "Integrated characteristic curves of the constant-pressure hydraulic power take-off in wave energy conversion" (International Journal of Electrical Power and Energy Systems, 2019, Volume 117, Article Number 105730) suggests that the operating curve within the CPHPTO integrated characteristic curve can be used to guide efficient and stable operation. The operating curve includes constant flow lines, output limit lines, and constant efficiency lines. The output limit line passes through a high-efficiency stable region at different flow rates. The output limit line consists of two segments: the first segment is limited by the design output (i.e., the rated power of the three-phase permanent magnet synchronous generator); the second segment is limited by the design speed (i.e., the rated speed of the three-phase permanent magnet synchronous generator) and the design system oil pressure (i.e., the design hydraulic motor inlet oil pressure. Since the hydraulic motor outlet is connected to a low-pressure tank, the outlet oil pressure is much lower than the inlet oil pressure, so the design system oil pressure can also be considered the design hydraulic motor inlet and outlet pressure differential). When the instantaneous output exceeds the design output, the system flow exceeds the design flow, and the flow needs to be limited to the design flow through the speed control valve, thereby limiting the output to the design output. When the instantaneous output is less than the design output, it operates according to the second section output limit line, and the system oil pressure and speed are stabilized at the design system oil pressure and design speed respectively through constant speed and constant pressure control.

[0005] The invention patent "Method for Obtaining Comprehensive Characteristic Curves for a Wave-Powered Hydraulic PTO System" (Patent No.: ZL201710346136.1, Authorization Announcement Date: June 19, 2020) further states that the hydraulic motor's output shaft speed can be maintained at the rated speed of the three-phase permanent magnet synchronous generator by adjusting the hydraulic motor's displacement. The mechanical torque of the main shaft can be adjusted through vector control of the three-phase permanent magnet synchronous generator to stabilize the hydraulic motor's inlet and outlet pressure differential, ultimately achieving constant speed and pressure control. However, the patent does not detail the controller structure design and control process of this constant speed and pressure control strategy.

[0006] Currently, researchers have proposed several constant-speed and constant-pressure control techniques for CPHPTOs and conducted simulation studies. The paper "Research on Key Technologies of Buoyant Pendulum Wave Energy Power Generation Devices" (doctoral dissertation, Zhejiang University, published in 2011) suggests that variable motor displacement control or variable electrical load control can achieve constant speed and pressure, as well as stable output power, under ideal periodic step wave forces. Variable electrical load control, in particular, offers greater operational stability. The paper "Operation characteristics and methods of the hydraulic power take-off system" (Transactions of the Institute of Measurement and Control, 2020, Volume 43, Issue 5, Article Number 014233122093435) addresses the ideal sinusoidal reciprocating motion of the hydraulic cylinder piston rod and an AC resistive load. The paper uses a relief valve to limit the oil pressure in the CPHPTO system, and uses motor displacement PID control to achieve stable speed and output power.

[0007] The above constant speed and constant pressure control technology has the following two defects:

[0008] 1) The research process oversimplified the CPHPTO input, resulting in overly idealized simulation results that differ significantly from actual conditions. Consequently, the proposed constant speed and constant pressure control technology is not practically feasible and cannot be used to guide actual operation. The paper "Research on Key Technologies of Buoyant Pendulum Wave Energy Generation Devices" simplifies the input wave force to a periodic step force, while the paper "Operation Characteristics and Methods of the Hydraulic Power Take-off System" simplifies the hydraulic cylinder input displacement to a sinusoidal reciprocating motion. Neither paper effectively studies the input conditions under actual irregular wave conditions.

[0009] 2) Unable to simultaneously maintain constant system oil pressure and speed. The document "Research on Key Technologies for Buoyant Pendulum Wave Energy Generation Devices" utilizes only a single variable motor displacement control or variable electrical load control. This single control method can only stabilize a single operating parameter (i.e., system oil pressure or speed). The other operating parameter is bound to fluctuate under actual irregular wave conditions. The document "Operation Characteristics and Methods of the Hydraulic Power Take-off System" only limits the upper limit of the CPHPTO system oil pressure through a relief valve and does not implement effective feedback control of the system oil pressure. Therefore, it can only achieve constant speed. Pressure inevitably fluctuates in real time under actual irregular wave conditions. Only when overflow occurs under high sea conditions will the system oil pressure stabilize at the overflow pressure.

[0010] While researching CPHPTO constant-speed and constant-pressure control technology, the inventors discovered that the fundamental problem with the existing technology was that it failed to account for the potential dramatic fluctuations in system oil pressure under actual irregular wave conditions and limited accumulator volume. For example, when sea conditions are mild, causing the system oil pressure to fall below the accumulator charging pressure, the accumulator cannot operate normally, and the system oil pressure will fluctuate dramatically. When sea conditions are severe, causing the system oil pressure to far exceed the design pressure, the accumulator's pressure-stabilizing ability decreases, and the amplitude of the system oil pressure increases under the same charge and discharge volume. However, due to the unique pressure-flow-speed coupling characteristics of the CPHPTO, fluctuations in system oil pressure and speed are correlated, but they do not determine each other. For example, while the system oil pressure can be maintained constant through control, input power fluctuations in irregular sea conditions and the limited function of the accumulator cause fluctuations in hydraulic power and flow. These flow fluctuations are transmitted to the hydraulic motor output shaft and the synchronously rotating three-phase permanent magnet synchronous generator shaft according to the relationship "flow = speed * hydraulic motor displacement" (ignoring efficiency losses), causing speed to be unstable. Furthermore, while the speed can be maintained constant through control, input power fluctuations in irregular sea conditions and the limited function of the accumulator require synchronous fluctuations in the hydraulic motor load torque to maintain input and output power balance. According to the relationship "system oil pressure = hydraulic motor load torque * 2 * pi ÷ hydraulic motor displacement" (ignoring efficiency losses), system oil pressure will also fluctuate and become unstable. Therefore, it is impossible to achieve constant system oil pressure and speed simultaneously through single control. Summary of the Invention

[0011] The purpose of the present invention is to provide a wave energy power generation hydraulic PTO constant speed and pressure control method based on dual-parameter joint regulation, so as to solve the problem that the existing CPHPTO constant speed and pressure control technology cannot achieve synchronous constant system oil pressure and speed under actual irregular wave conditions.

[0012] To achieve the above object, the present invention provides the following technical solutions:

[0013] The present invention also provides a wave energy power generation hydraulic PTO constant speed and pressure control method based on dual parameter joint adjustment, which is characterized in that the method includes: collecting the system oil pressure signal p of the main oil circuit through a pressure transmitter, and sending the oil pressure signal p to the oil pressure closed-loop regulation module; measuring the torque signal M of the input shaft of the three-phase permanent magnet synchronous generator through a speed torque meter; g and speed signal n, and the signal M g The signal n is sent to the oil pressure open-loop regulation module, and the signal n is sent to the oil pressure closed-loop regulation module; the electromagnetic torque of the three-phase permanent magnet synchronous generator is controlled by the three-phase PWM rectifier, and the speed n is indirectly adjusted; the three-phase current signal i at the outlet of the three-phase permanent magnet synchronous generator is collected by the generator vector controller a i b i c , and output SVPWM signal to the three-phase PWM rectifier, while receiving the speed signal n and setting speed n r ; Get the set oil pressure p through the oil pressure open loop regulation module r and set speed n r , and calculate the fractional displacement signal x m ; Get the set oil pressure p through the oil pressure closed loop regulation module r and set speed n r , and calculate the fractional displacement signal x m ; Adjust the electric drive module through displacement and according to the fractional displacement signal x m The size of the linear adjustment control current is sent to the solenoid valve of the variable displacement hydraulic motor to control the displacement of the motor; through the open-closed loop mode switch, the oil pressure open-loop adjustment and oil pressure closed-loop adjustment are switched, and the fractional displacement signal x ... m Sent to the displacement adjustment electric drive module.

[0014] The present invention further provides that when the oil pressure open-loop regulation module outputs the fractional displacement signal, the fractional displacement intermediate value x is calculated by the formula mm , the formula is: ; Fractional displacement median x mm After the saturation link is limited, the fractional displacement calculation value x is obtained m0 And sent to the condition judgment link, the condition judgment link judges whether the relative speed difference △ is less than the set speed difference △0. If △≤△0, then output Otherwise, output the given fractional displacement The output result of the condition judgment link is processed discretely by the zero-order hold link and becomes the fractional displacement signal x m Output.

[0015] The present invention further provides that when the oil pressure closed-loop regulation module outputs the fractional displacement signal, the system oil pressure signal p and the set oil pressure p r The deviation is calculated by discrete PI regulator to calculate the intermediate value of fractional displacement x mm , the formula is: , where is the proportionality coefficient, is the integration coefficient, is the sampling time of discrete PI regulator, the intermediate value of fractional displacement The fractional displacement calculation value is obtained after the saturation link is limited And sent to the condition judgment link, the condition judgment link judges whether the relative speed difference △ is less than the set speed difference △0. If △≤△0, then output Otherwise, output the given fractional displacement The output result of the condition judgment link is processed discretely by the zero-order hold link and becomes the fractional displacement signal x m Output.

[0016] The present invention further provides that the calculation formula of the relative speed difference Δ is as follows:

[0017] .

[0018] The present invention further provides that the upper and lower limits of the saturation link are 1 and the minimum fractional displacement of the hydraulic motor respectively.

[0019] The present invention further provides that the set speed difference Δ0 needs to be greater than the sum of the relative value of the steady-state error and the relative value of the disturbance deviation of the speed n.

[0020] The present invention further provides that the given fractional displacement Any value between the minimum fractional displacement of the hydraulic motor and 1.

[0021] The present invention further provides that the sampling time of the zero-order holding link needs to be greater than the duration of the adjustment process of the hydraulic motor displacement from the minimum value to the maximum value or from the maximum value to the minimum value.

[0022] The present invention further provides that the sampling time of the discrete PI regulator is less than or equal to the sampling time of the zero-order hold link, and is adjusted according to the requirements of calculation accuracy.

[0023] The present invention further provides that the speed loop PI regulator is based on the speed signal n and the set speed n r The deviation of the given q-axis current signal is calculated Then, Clark transform and Park transform the measured three-phase current values ​​to the current loop PI regulator. Convert to two-phase stationary coordinate system Next , and further converted into a synchronous rotating coordinate system Next Sent to the current loop PI regulator; again, the current loop PI regulator sets the given d-axis current signal , and according to and The deviation of the given voltage signal is calculated ; Then, the inverse Park transform will Convert to Under the coordinates ;Finally, the SVPWM algorithm is based on The output PWM signal controls the three-phase PWM rectifier.

[0024] Beneficial effects of the present invention: 1. It can realize decoupling control of the rotation speed and system oil pressure under actual irregular wave conditions, and truly achieve constant speed and constant pressure control effects.

[0025] 2. The system oil pressure control can be stabilized through two forms: open-loop oil pressure control and closed-loop oil pressure control. Both forms can be configured individually or in combination according to the actual needs of the user. Among them, the open-loop control structure is simple and does not require system oil pressure signal feedback, which meets basic needs. The closed-loop control structure has a better control effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0027] Figure 1 This is a mechanical structure diagram of a buoyancy pendulum wave energy power generation device based on a constant pressure hydraulic PTO;

[0028] Figure 2 This is the structural block diagram of the wave energy generation hydraulic PTO constant speed and constant pressure control based on dual parameter joint adjustment;

[0029] Figure 3 This is the structural block diagram of the oil pressure open-loop regulation module;

[0030] Figure 4 This is the structural block diagram of the oil pressure closed-loop regulation module;

[0031] Figure 5 This is the structural block diagram of the generator vector controller;

[0032] Figure 6 It is the speed signal change curve under constant speed and constant pressure control;

[0033] Figure 7 This is the system oil pressure signal change curve under constant speed and constant pressure control;

[0034] Figure 8 The actual operating curve of the constant pressure hydraulic PTO with the generator vector controlled and the motor displacement not controlled;

[0035] Figure 9 This is the actual operating curve of the constant pressure hydraulic PTO under constant speed and pressure control and oil pressure open loop regulation;

[0036] Figure 10 This is the actual operating curve of the constant pressure hydraulic PTO under constant speed and pressure control and oil pressure closed loop regulation;

[0037] Figure 1: buoyancy pendulum; 2: guide rod assembly; 3: rack; 4: gear; 5: main shaft; 6:1: hydraulic cylinder 1; 6:2: hydraulic cylinder 2; 7:1: one-way valve 1; 7:2: one-way valve 2; 7:3: one-way valve 3; 7:4: one-way valve 4; 8: high-pressure accumulator; 9: speed regulating valve; 10: variable displacement hydraulic motor; 11: three-phase permanent magnet synchronous generator; 12: overflow valve; 13: low-pressure oil tank; 14: pressure transmitter; 15: speed torque meter; 16: three-phase PWM rectifier; 17: direct current Flow bus; 18-displacement adjustment electric drive module; 19-open-closed loop mode switching switch; 20-oil pressure open-loop adjustment module; 21-oil pressure closed-loop adjustment module; 22-generator vector controller; 23-main oil circuit; 24-1-saturation link; 24-2-saturation link; 25-1-conditional judgment link; 25-2-conditional judgment link; 26-1-zero-order holding link; 26-2-zero-order holding link; 27-discrete PI regulator; 28-speed loop PI regulator; 29-current loop PI regulator. DETAILED DESCRIPTION

[0038] The following will describe the implementation methods of the present application in detail with reference to the accompanying drawings and examples, so that the implementation process of how the present application applies technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly.

[0039] Through CPHPTO irregular wave simulation research, the inventors found that by first using generator vector control to stabilize the speed, and then implementing motor displacement control to stabilize the oil pressure when the speed deviation is less than a certain threshold, the speed and system oil pressure can be kept synchronously constant under actual irregular wave sea conditions, achieving a true constant speed and constant pressure control effect.

[0040] The present invention does not consider adopting the constant speed and constant pressure control strategy of generator vector control to stabilize oil pressure and motor displacement control to stabilize speed as described in the invention patent "Method for obtaining comprehensive characteristic curves of wave power generation hydraulic PTO system". The reason is that: the physical limitations of the maximum and minimum displacement of the motor make the speed stabilization ability of the motor displacement control limited under the condition of large flow changes, and indirect control of oil pressure through vector control can easily cause the motor to reverse and pump oil.

[0041] Therefore, the following technical solutions are proposed:

[0042] The present invention provides a wave energy power generation hydraulic PTO constant speed and pressure control method based on dual-parameter joint regulation, and is aimed at a wave energy power generation device adopting a constant pressure hydraulic PTO structure.

[0043] Example Investigation Figure 1 The illustrated buoyant pendulum wave energy power generation device, based on a constant-pressure hydraulic PTO, has a mechanical structure comprising: a buoyant pendulum body 1; a guide rod assembly 2; a rack 3; a gear 4; a main shaft 5; and a constant-pressure hydraulic PTO. The constant-pressure hydraulic PTO includes: hydraulic cylinder 1 6-1; hydraulic cylinder 2 6-2; check valve 1 7-1; check valve 2 7-2; check valve 3 7-3; check valve 4 7-4; a high-pressure accumulator 8; a speed regulating valve 9; a variable-displacement hydraulic motor 10; a three-phase permanent magnet synchronous generator 11; a relief valve 12; a low-pressure oil tank 13; and a main oil circuit 23. The buoyant pendulum body 1 is mounted on the main shaft 5 and can rotate relative to it. The cylinder body of hydraulic cylinder 1 (6-1), the cylinder body of hydraulic cylinder 2 (6-2), check valve 1 (7-1), check valve 2 (7-2), check valve 3 (7-3), check valve 4 (7-4), high-pressure accumulator 8, speed regulating valve 9, variable-displacement hydraulic motor 10, three-phase permanent magnet synchronous generator 11, relief valve 12, low-pressure oil tank 13, pressure transmitter 14, speed and torque meter 15, and main oil line 23 are all fixed to the inner wall of the buoyant pendulum body 1. Gear 4 is fixed to the main shaft 5 and meshes with rack 3. A rib is welded to the center of the back of rack 3, and its sides are respectively connected to the piston rods of hydraulic cylinder 1 (6-1) and hydraulic cylinder 2 (6-2). The guide rod assembly 2 consists of two upper and lower guide rods, each of which is fixed to the cylinder body of hydraulic cylinder 1 (6-1) and hydraulic cylinder 2 (6-2). The ribs of rack 3 have through-holes, through which guide rod assembly 2 passes, forming a moving pair with linear bearings and rack 3. The oil port of hydraulic cylinder 1 6-1 is connected to the oil inlet of check valve 1 7-1 and the oil outlet of check valve 3 7-3. The oil port of hydraulic cylinder 2 6-2 is connected to the oil inlet of check valve 2 7-2 and the oil outlet of check valve 4 7-4. The oil outlets of check valve 1 7-1 and check valve 2 7-2 are connected to the oil inlet of main oil circuit 23, while the oil inlet of check valve 3 7-3 and check valve 4 7-4 are connected to the oil outlet of main oil circuit 23. An oil circuit also branches off from the oil inlet of main oil circuit 23, connecting to the oil inlet of relief valve 12. The oil outlet of relief valve 12 is connected to low-pressure oil tank 13. An oil circuit also branches off from the oil outlet of main oil circuit 23, connecting to the low-pressure oil tank 13. A high-pressure accumulator 8, a speed regulating valve 9, a pressure transmitter 14, and a variable-displacement hydraulic motor 10 are sequentially installed between the inlet and outlet of the main oil circuit 23. Couplings connect the output shaft of the variable-displacement hydraulic motor 10 to the input shaft of the speed and torque meter 15, as well as the output shaft of the speed and torque meter 15 to the input shaft of the three-phase permanent magnet synchronous generator 11.

[0044] The operating principle of the buoyant pendulum wave energy generator based on a constant-pressure hydraulic PTO is as follows: A buoyant pendulum body 1 is completely submerged in seawater and, under the influence of buoyancy torque, stands upright on the main shaft 5. When incident waves act on the front of the buoyant pendulum body 1, it swings about the main shaft 5. The meshing gear 4 and rack 3 convert this swinging motion of the buoyant pendulum body 1 relative to the main shaft 5 into translational motion of the rack 3 relative to the guide rod assembly 2. The rack 3, via its back ribs, further pushes the piston rods of hydraulic cylinders 1 (6-1) and 2 (6-2) relative to the cylinder bodies, causing the oil chambers to expand and absorb oil or compress and generate high-pressure oil. When the rack 3 rib pushes the piston rod of hydraulic cylinder 2 (6-2) to compress the oil chamber of hydraulic cylinder 2 (6-2), the generated high-pressure oil enters the main oil circuit 23 inlet through check valve 1 (7-1), passes through high-pressure accumulator 8, speed control valve 9, pressure transmitter 14, and variable displacement hydraulic motor 10, reaches the main oil circuit 23 outlet, and then passes through check valve 4 (7-4) to enter the oil chamber of hydraulic cylinder 1 (6-1). Similarly, when the rack 3 rib pushes the piston rod of hydraulic cylinder 1 (6-1) to compress the oil chamber of hydraulic cylinder 1 (6-1), the generated high-pressure oil enters the main oil circuit 23 inlet through check valve 2 (7-2), passes through high-pressure accumulator 8, speed control valve 9, pressure transmitter 14, and variable displacement hydraulic motor 10, reaches the main oil circuit 23 outlet, and then passes through check valve 3 (7-3) to enter the oil chamber of hydraulic cylinder 2 (6-2). The four check valves act as a rectifier, converting the bidirectional flow of high-pressure oil into a unidirectional flow in the main oil circuit 23. The overflow valve 12 is used to prevent the constant pressure hydraulic PTO from overpressure, and the overflow is opened when the inlet oil pressure of the main oil circuit 23 reaches the upper limit of the working oil pressure. The high-pressure accumulator 8 is used to stabilize the oil pressure at the inlet of the main oil circuit 23, and thus stabilize the flow of the main oil circuit 23. The speed control valve 9 is used to adjust the flow of the main oil circuit 23 and participate in the power generation control. At the same time, when the flow of the main oil circuit 23 reaches the upper limit of the flow, in order to avoid the three-phase permanent magnet synchronous generator 11 from overspeeding, the flow can be limited by the speed control valve 9. The variable displacement hydraulic motor 10 is used to convert hydraulic energy into rotational mechanical energy, and the three-phase permanent magnet synchronous generator 11 is used to convert rotational mechanical energy into electrical energy output. The low-pressure oil tank 13 is used to stabilize the oil pressure at the outlet of the main oil circuit 23, replenish system leakage, and eliminate short-term negative pressure.

[0045] The constant speed and constant pressure control structure of the constant pressure hydraulic PTO is as follows Figure 2As shown, it includes a pressure transmitter 14 and a speed and torque meter 15 for signal acquisition, a three-phase PWM rectifier 16 for generator vector control, a DC bus 17, and a generator vector controller 22, a displacement control electric drive module 18 for motor displacement control, an open-closed loop mode switch 19, an oil pressure open-loop control module 20, and an oil pressure closed-loop control module 21. The pressure transmitter 14 is installed between the oil outlet of the speed control valve 9 and the oil inlet of the variable displacement hydraulic motor 10, and collects the system oil pressure signal p of the main oil circuit 23 to the oil pressure closed-loop control module 21. The speed and torque meter 15 is installed between the output shaft of the variable displacement hydraulic motor 10 and the input shaft of the three-phase permanent magnet synchronous generator 11, and measures the torque signal M of the input shaft of the three-phase permanent magnet synchronous generator 11. g The speed signal n is sent to the oil pressure open loop regulation module 20, and the speed signal n is branched to the generator vector controller 22. r The data is sent to the oil pressure open loop control module 20 and the oil pressure closed loop control module 21 respectively. r The signals are sent to the oil pressure open loop control module 20, the oil pressure closed loop control module 21 and the generator vector controller 22. The oil pressure open loop control module 20 and the oil pressure closed loop control module 21 calculate the fractional displacement signal x m After that, it is sent to the displacement regulating electric drive module 18 through the open-closed loop mode switching switch 19. The displacement regulating electric drive module 18 adjusts the displacement signal x according to the fractional displacement signal. m The size of the linear control current is adjusted and sent to the solenoid valve of the variable displacement hydraulic motor 10 to control the motor displacement. The open-closed loop mode switch 19 is used to switch between oil pressure open-loop regulation and oil pressure closed-loop regulation according to user needs. The generator vector controller 22 collects the three-phase current signal at the output of the three-phase permanent magnet synchronous generator 11. , and outputs the SVPWM signal to the three-phase PWM rectifier 16, which controls the electromagnetic torque of the three-phase permanent magnet synchronous generator 11, indirectly realizing the adjustment of the speed n.

[0046] The internal structure of the oil pressure open-loop regulation module 20 is as follows Figure 3 As shown. According to formula (1), the intermediate value of fractional displacement is calculated :

[0047] (1)

[0048] In formula (1), Indicates the maximum displacement of the hydraulic motor provided by the equipment manufacturer. Indicates the hydraulic motor's set mechanical efficiency. Fractional displacement median value After the saturation step 24-1, the fractional displacement calculation value is obtained And sent to the condition judgment link 25-1. The condition judgment link 25-1 judges whether the relative speed difference △ is less than the set speed difference △0. If △≤△0, then output Otherwise, output the given fractional displacement The output result of the 1# condition judgment link 25-1 is processed discretely by the zero-order hold link 26-1 and becomes the fractional displacement signal x m Output.

[0049] The internal structure of the oil pressure closed-loop regulation module 21 is as follows Figure 4 As shown. System oil pressure signal p and set oil pressure p r The deviation is calculated by discrete PI regulator 27 to calculate the intermediate value of fractional displacement , the formula is: , where is the proportionality coefficient, is the integration coefficient, The sampling time of discrete PI regulator. The intermediate value of fractional displacement After the saturation step 24-2, the fractional displacement calculation value is obtained And send it to 2# condition judgment link 25-2. Condition judgment link 25-2 judges whether the relative speed difference △ is less than the set speed difference △0. If △≤△0, then output Otherwise, output the given fractional displacement The output result of the 2# condition judgment link 25-2 is processed discretely by the zero-order hold link 26-2 and becomes the fractional displacement signal x m Output.

[0050] The hydraulic motor sets the mechanical efficiency It is related to the energy characteristics of the hydraulic motor and can generally be taken as 0.9 or above.

[0051] The upper and lower limits of the saturation link 24 - 1 and the saturation link 24 - 2 are 1 and the minimum fractional displacement of the hydraulic motor, respectively.

[0052] The relative speed difference Δ is calculated according to formula (2):

[0053] (2);

[0054] The set speed difference Δ0 must be greater than the sum of the relative value of the steady-state error and the relative value of the disturbance deviation of the speed n, so as to avoid the output values ​​of the 1# condition judgment link 25-1 and the 2# condition judgment link 25-2 being too large when the speed n is disturbed. and Switching back and forth between the two affects the stability of constant speed and constant pressure control, and it can generally be taken as 0.05.

[0055] The given fractional displacement It can be any value between the minimum fractional displacement of the hydraulic motor provided by the equipment manufacturer and 1.

[0056] The sampling time of the zero-order holding link 26-1 and the zero-order holding link 26-2 must be greater than the adjustment process time of the hydraulic motor displacement from the minimum to the maximum or from the maximum to the minimum, generally greater than 0.05s, to prevent the actual displacement adjustment speed from being unable to keep up with the fractional displacement signal x m The speed of change.

[0057] The sampling time of the discrete PI regulator 27 is generally less than or equal to the sampling time of the zero-order hold link 26 - 1 and the zero-order hold link 26 - 2 , and can be adjusted according to the requirements of calculation accuracy.

[0058] The internal structure of the generator vector controller is as follows Figure 5 As shown, the speed loop PI regulator 28, the current loop PI regulator 29, the SVPWM algorithm, the Clark transformation, the Park transformation and the inverse Park transformation are included. First, the speed loop PI regulator 28 adjusts the speed according to the speed signal n and the set speed n. r The deviation of the given q-axis current signal is calculated Then, the three-phase current values ​​are measured by Clark transformation and Park transformation. Convert to two-phase stationary coordinate system Next , and further converted into a synchronous rotating coordinate system Next Sent to the current loop PI regulator 29. Again, the current loop PI regulator 29 sets the given d-axis current signal , and according to and The deviation of the given voltage signal is calculated Then, the inverse Park transform will Convert to Under the coordinates Finally, the SVPWM algorithm is based on The output PWM signal controls the three-phase PWM rectifier 16 .

[0059] The described method for controlling a wave power generation hydraulic PTO constant speed and pressure based on dual-parameter joint adjustment achieves excellent speed and pressure stability. The control effect is demonstrated below through a simulation of irregular wave conditions. The key parameter settings are shown in Table 1.

[0060] Table 1 Key parameter settings

[0061]

[0062] The simulation results are as follows Figures 6 to 10 As shown. Among them, Figure 6 and Figure 7 They are the speed signal change curve and the system oil pressure signal change curve under constant speed and constant pressure control. Figure 6 and Figure 7 It can be seen that the wave energy generation hydraulic PTO constant speed and constant pressure control based on dual parameter joint adjustment can stabilize the speed signal at the set speed n r Make the system oil pressure signal stable at the set oil pressure p r Nearby, the performance of the oil pressure closed-loop regulation module is better than that of the oil pressure open-loop regulation module, the overshoot of the system oil pressure signal transition process is small, and there is no steady-state error fluctuation. Figures 8 to 10 The actual operating curves of the constant pressure hydraulic PTO are respectively the generator vector control and the motor displacement is not controlled, the constant speed and constant pressure control and the oil pressure open loop regulation, and the constant speed and constant pressure control and the oil pressure closed loop regulation, which are drawn on the flow q-output N plane. It should be noted that Figures 8 to 10 The speed signal n of the actual operation curve is basically stable at the set speed n r The error is less than ±1%. Figures 8 to 10 In addition to the actual operation curve of the constant pressure hydraulic PTO, there is also a maximum flow line (i.e. the horizontal straight line q=q max ), the minimum flow line (i.e. the horizontal straight line q=q min ), the maximum displacement line (i.e. the oblique straight line D=D m ), minimum displacement line (i.e. oblique straight line D=0.3D m ), high pressure accumulator charging pressure line (i.e. oblique straight line p=0.8p r ) and the output limit line (i.e. straight line p=p r and the straight line N=N r The broken line is formed by the high-pressure accumulator charging pressure line, the maximum displacement line, and the minimum displacement line, wherein the area enclosed by the high-pressure accumulator charging pressure line, the maximum displacement line, and the minimum displacement line is the stable operating area, and the area through which the output limit line passes is the high-efficiency and stable area of ​​the constant-pressure hydraulic PTO. Therefore, the actual operating curve of the ideal state line constant-pressure hydraulic PTO must run along the output limit line. In the case of generator vector control and uncontrolled motor displacement, the actual operating curve of the constant-pressure hydraulic PTO and the output limit line do not overlap at all, and the period of operation in the unstable operating area is long, making it difficult to guarantee the economy and safety of the constant-pressure hydraulic PTO operation. In the case of constant speed and constant pressure control with open-loop oil pressure regulation, or constant speed and constant pressure control with closed-loop oil pressure regulation, the actual operating curve of the constant-pressure hydraulic PTO can move along the output limit line, and most of the time it runs in the stable operating area, and the economy and safety of the constant-pressure hydraulic PTO operation can be guaranteed. Constant speed and constant pressure control with closed-loop oil pressure regulation has a better adjustment effect, and a higher degree of overlap with the output limit line.

[0063] For example, certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different terms to refer to the same component. This specification and claims do not use differences in names as a way to distinguish components, but use differences in the functions of the components as the criteria for distinction. For example, "including" mentioned throughout the specification and claims is an open term, so it should be interpreted as "including but not limited to". "Approximately" means that within an acceptable error range, those skilled in the art can solve the technical problem within a certain error range and basically achieve the technical effect.

[0064] It should be noted that the terms "include," "comprises," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a product or system comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such product or system. In the absence of further limitations, an element defined by the phrase "comprising a..." does not exclude the presence of other identical elements in the product or system comprising the element.

[0065] The foregoing description shows and describes several preferred embodiments of the present invention. However, as previously stated, it should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. Rather, the present invention can be used in various other combinations, modifications, and environments and can be modified within the scope of the inventive concept described herein by the teachings above or by techniques or knowledge in the relevant art. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention are intended to be within the scope of the appended claims.

Claims

1. A wave energy power generation hydraulic PTO constant speed and constant pressure control method based on dual parameter joint adjustment, characterized in that: The method comprises: collecting the system oil pressure signal p of the main oil circuit through a pressure transmitter, and sending the oil pressure signal p to the oil pressure closed-loop regulation module; measuring the torque signal M of the input shaft of the three-phase permanent magnet synchronous generator through a speed torque meter; g and speed signal n, and the signal M g The signal n is sent to the oil pressure open-loop regulation module, and the signal n is sent to the oil pressure closed-loop regulation module; the electromagnetic torque of the three-phase permanent magnet synchronous generator is controlled by the three-phase PWM rectifier, and the speed n is indirectly adjusted; the three-phase current signal i at the outlet of the three-phase permanent magnet synchronous generator is collected by the generator vector controller a i b i c , and output SVPWM signal to the three-phase PWM rectifier, while receiving the speed signal n and setting speed n r ; Get the set oil pressure p through the oil pressure open loop regulation module r and set speed n r , and calculate the fractional displacement signal x m ; Get the set oil pressure p through the oil pressure closed loop regulation module r and set speed n r , and calculate the fractional displacement signal x m ; Adjust the electric drive module through the displacement and according to the fractional displacement signal x m The size of the linear adjustment control current is sent to the solenoid valve of the variable displacement hydraulic motor to control the displacement of the motor; through the open-closed loop mode switch, the oil pressure open-loop adjustment and oil pressure closed-loop adjustment are switched, and the fractional displacement signal x ... m Sent to the displacement adjustment electric drive module.

2. A wave energy power generation hydraulic PTO constant speed and constant pressure control method based on dual parameter joint adjustment according to claim 1, characterized in that: When the oil pressure open-loop regulation module outputs the fractional displacement signal, the fractional displacement intermediate value x is calculated by the formula mm , the formula is: ; Fractional displacement median x mm After the saturation link is limited, the fractional displacement calculation value x is obtained m0 And sent to the condition judgment link, the condition judgment link judges whether the relative speed difference △ is less than the set speed difference △0. If △≤△0, then output Otherwise, output the given fractional displacement The output result of the condition judgment link is processed discretely by the zero-order hold link and becomes the fractional displacement signal x m Output; Indicates the maximum displacement of the hydraulic motor provided by the equipment manufacturer. Indicates the set mechanical efficiency of the hydraulic motor.

3. The wave energy power generation hydraulic PTO constant speed and constant pressure control method based on dual parameter joint adjustment according to claim 1 is characterized in that: When the oil pressure closed-loop regulation module outputs the fractional displacement signal, the system oil pressure signal p and the set oil pressure p r The deviation is calculated by discrete PI regulator to calculate the intermediate value of fractional displacement x mm , the formula is: , where is the proportionality coefficient, is the integration coefficient, is the sampling time of discrete PI regulator, the intermediate value of fractional displacement The fractional displacement calculation value is obtained after the saturation link is limited And sent to the condition judgment link, the condition judgment link judges whether the relative speed difference △ is less than the set speed difference △0. If △≤△0, then output Otherwise, output the given fractional displacement The output result of the condition judgment link is processed discretely by the zero-order hold link and becomes the fractional displacement signal x m Output.

4. A wave energy power generation hydraulic PTO constant speed and constant pressure control method based on dual parameter joint adjustment according to claim 2 or 3, characterized in that: The calculation formula of the relative speed difference Δ is as follows: 。 5. A wave energy power generation hydraulic PTO constant speed and constant pressure control method based on dual parameter joint adjustment according to claim 2 or 3, characterized in that: The upper and lower limits of the saturation link are 1 and the minimum fractional displacement of the hydraulic motor respectively.

6. A wave energy power generation hydraulic PTO constant speed and constant pressure control method based on dual parameter joint adjustment according to claim 2 or 3, characterized in that: The set speed difference Δ0 must be greater than the sum of the relative value of the steady-state error and the relative value of the disturbance deviation of the speed n.

7. A wave energy power generation hydraulic PTO constant speed and constant pressure control method based on dual parameter joint adjustment according to claim 2 or 3, characterized in that: The given fractional displacement Any value between the minimum fractional displacement of the hydraulic motor and 1.

8. A wave energy power generation hydraulic PTO constant speed and constant pressure control method based on dual parameter joint adjustment as claimed in claim 2 or 3, characterized in that: The sampling time of the zero-order holding link must be greater than the duration of the adjustment process of the hydraulic motor displacement from the minimum value to the maximum value or from the maximum value to the minimum value.

9. A wave energy power generation hydraulic PTO constant speed and constant pressure control method based on dual parameter joint adjustment as claimed in claim 3, characterized in that: The sampling time of the discrete PI regulator is ≤ the sampling time of the zero-order hold link, and is adjusted according to the requirements of calculation accuracy.

10. The method for controlling a wave energy power generation hydraulic PTO constant speed and pressure based on dual parameter joint adjustment according to claim 1, characterized in that: The speed loop PI regulator is based on the speed signal n and the set speed n r The deviation of the given q-axis current signal is calculated Then, Clark transform and Park transform the measured three-phase current values ​​to the current loop PI regulator. Convert to two-phase stationary coordinate system Next , and further converted into a synchronous rotating coordinate system Next Sent to the current loop PI regulator; again, the current loop PI regulator sets the given d-axis current signal , and according to and The deviation of the given voltage signal is calculated ; Then, the inverse Park transform will Convert to Under the coordinates ;Finally, the SVPWM algorithm is based on The output PWM signal controls the three-phase PWM rectifier.

Images