Wave energy power generation hydraulic PTO constant speed and constant pressure control system based on double parameter joint debugging

Abstract

The application provides a wave energy power generation hydraulic PTO constant-speed constant-pressure control system based on double-parameter joint debugging, which comprises a pressure transmitter, a rotating speed and torque instrument, a three-phase PWM rectifier, a generator vector controller, an oil pressure open-loop regulation module, an oil pressure closed-loop regulation module, a displacement regulation electric drive module, and an open-closed loop mode switching switch. m The open-closed loop mode switching switch is used for switching between the oil pressure open-loop regulation and the oil pressure closed-loop regulation and sending a fractional displacement signal x to the displacement regulation electric drive module. The application can realize decoupling control of rotating speed and system oil pressure under actual irregular wave sea conditions, truly realizes constant-speed and constant-pressure control effect, realizes stable system oil pressure control through oil pressure open-loop control and oil pressure closed-loop control, and the two forms can be configured singly or entirely according to actual user demand, wherein the open-loop control structure is simple, does not need system oil pressure signal feedback, meets basic demand, and the closed-loop control structure has better control effect.

Description

Technical Field

[0001] This 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 constant pressure control system based on dual-parameter joint regulation. Background Technology

[0002] Constant-pressure hydraulic PTO (CPHPTO) is a common transmission method in wave energy power generation devices. CPHPTO adds a high-pressure accumulator between the hydraulic cylinder and the motor, thus significantly reducing fluctuations in internal oil pressure, flow rate, and motor speed, thereby improving energy conversion efficiency. A disadvantage of CPHPTO is that it is difficult to rapidly adjust the PTO force (torque) by changing the motor displacement. Currently, CPHPTO is widely used in serpentine devices, wavestar devices, raft devices, heave float devices, and various pendulum devices, such as SEAREV devices, eagle devices, buoyancy pendulum devices, floating pendulum devices, and resonant devices.

[0003] Although the CPHPTO has high energy conversion efficiency and relatively stable operating point, its internal nonlinear energy loss cannot be ignored. Furthermore, under complex irregular sea conditions and limited nominal capacity of the high-voltage accumulator, the system's operating point can still fluctuate considerably. Therefore, it is still necessary to comprehensively examine all possible operating points and use operational control to ensure that the CPHPTO operates in the efficient and stable region, 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" (Journal article, International Journal of Electrical Power and Energy Systems, 2019, Volume 117, Article No. 105730) points out that the operating curves in the integrated characteristic curves of CPHPTO can be used to guide the efficient and stable operation of CPHPTO. The operating curves include constant flow lines, output limit lines, and constant efficiency lines. The output limit line passes through the efficient and stable regions under 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), and 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 oil tank, the outlet oil pressure is much lower than the inlet oil pressure, therefore the design system oil pressure can also be considered as the design hydraulic motor inlet-outlet pressure difference). When the instantaneous output exceeds the design output, the system flow exceeds the design flow. 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 output limit line. Constant speed and constant pressure control is used to stabilize the system oil pressure and speed at the design system oil pressure and design speed, respectively.

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

[0006] Currently, some scholars have proposed constant speed and pressure control technologies based on CPHPTO and conducted simulation studies. The paper "Research on Key Technologies of Buoyancy Pendulum Wave Energy Generation Device" (doctoral dissertation, published by Zhejiang University, 2011) points out that by using variable motor displacement control or variable electrical load control, constant speed and pressure of CPHPTO, as well as stable output power, can be achieved under ideal periodic step wave force. Variable electrical load control provides better operational stability for CPHPTO. The paper "Operation characteristics and methods of the hydraulic power take-off system" (journal article, Transactions of the Institute of Measurement and Control, 2020, Volume 43, Issue 5, Article No. 014233122093435) addresses the ideal sinusoidal reciprocating motion of the hydraulic cylinder piston rod and AC resistive load. It uses an overflow valve to limit the oil pressure of the CPHPTO system and achieves stable speed and output power based on motor displacement PID control.

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

[0008] 1) The research process oversimplified the input of CPHPTO, resulting in overly idealized simulation results that differ significantly from reality. Therefore, the proposed constant speed and pressure control technology lacks practical operability and cannot be used to guide actual operation. The literature "Research on Key Technologies of Buoyancy Pendulum Wave Energy Generation Device" simplifies the input wave force to a periodic step force, while the literature "Operation characteristics and methods of the hydraulic power take-off system" simplifies the hydraulic cylinder input displacement to a sinusoidal reciprocating motion. Neither of these studies effectively addresses the input conditions under actual irregular wave sea conditions.

[0009] 2) It is impossible to simultaneously achieve constant system oil pressure and rotational speed. The literature "Research on Key Technologies of Buoyancy Pendulum Wave Energy Generation Device" only uses a single variable motor displacement control or variable electrical load control. A single control can only stabilize a single operating parameter (i.e., system oil pressure or rotational speed), while the other operating parameter will inevitably fluctuate under actual irregular wave sea conditions. The literature "Operation characteristics and methods of the hydraulic power take-off system" only limits the upper limit of CPHPTO system oil pressure through an overflow valve, without implementing effective feedback control of system oil pressure. Therefore, it can only achieve constant rotational speed, and the pressure will inevitably fluctuate in real time under actual irregular wave sea conditions. Only when an overflow occurs in large sea conditions will the system oil pressure stabilize at the overflow pressure.

[0010] When the inventors were researching CPHPTO constant speed and pressure control technology, they discovered that the fundamental problem with existing technologies was that they did not consider the drastic fluctuations in system oil pressure that might occur under actual irregular sea conditions and limited accumulator volume. For example, when the sea conditions are relatively calm, causing the system oil pressure to be lower than the accumulator charging pressure, the accumulator cannot work properly, and the system oil pressure will fluctuate drastically. When the sea conditions are relatively calm, causing the system oil pressure to be much higher than the design pressure, the accumulator's pressure stabilization capability decreases, and the amplitude of system oil pressure increases under the same charging and discharging volume. Due to CPHPTO's unique pressure-flow-speed coupling characteristics, fluctuations in system oil pressure and speed are correlated but not mutually determining. For example, when the system oil pressure is kept constant through control, fluctuations in input power under irregular sea conditions and the limited effect of the accumulator cause fluctuations in hydraulic power and flow rate. Flow rate fluctuations are transmitted to the output shaft of the hydraulic motor and the shaft of the synchronously rotating three-phase permanent magnet synchronous generator through the relationship "flow rate = speed * hydraulic motor displacement" (ignoring efficiency losses), making it impossible to keep the speed constant. Similarly, when the speed is kept constant through control, fluctuations in input power under irregular sea conditions and the limited effect of the accumulator require the hydraulic motor load torque to fluctuate synchronously to maintain the balance of input and output power. According to the relationship "system oil pressure = hydraulic motor load torque * 2 * pi ÷ hydraulic motor displacement" (ignoring efficiency losses), the system oil pressure will also fluctuate and cannot be kept constant. Therefore, it is practically impossible to achieve constant system oil pressure and speed simultaneously through a single control mechanism. Summary of the Invention

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

[0012] To achieve the above objectives, the present invention provides the following technical solution:

[0013] This invention provides a wave energy power generation hydraulic PTO constant speed and constant pressure control system based on dual-parameter joint regulation, including...

[0014] The pressure transmitter is used to acquire the system oil pressure signal p of the main oil circuit and send the oil pressure signal p to the oil pressure closed-loop regulation module;

[0015] A speed-torque meter is used to measure the torque signal M on the input shaft of a three-phase permanent magnet synchronous generator. g and the rotational speed signal n, and the signal M g The signal n is sent to the open-loop hydraulic pressure control module, and the signal n is sent to the closed-loop hydraulic pressure control module.

[0016] A three-phase PWM rectifier controls the electromagnetic torque of a three-phase permanent magnet synchronous generator, indirectly regulating the speed n.

[0017] The generator vector controller acquires the three-phase current signal i from the output of the three-phase permanent magnet synchronous generator. a i b i c It outputs an SVPWM signal to a three-phase PWM rectifier, and simultaneously receives the speed signal n and the set speed n. r ;

[0018] The hydraulic pressure open-loop regulating module obtains the set hydraulic pressure p. r and set speed n r And calculate the fractional displacement signal x m ;

[0019] The hydraulic pressure closed-loop control module obtains the set hydraulic pressure p. r and set speed n r And calculate the fractional displacement signal x m ;

[0020] Displacement regulation electric drive module, based on fractional displacement signal x m The magnitude of the control current is linearly adjusted and sent to the solenoid valve of the variable displacement hydraulic motor to control the motor displacement.

[0021] The open-loop / closed-loop mode switch toggles between open-loop and closed-loop hydraulic pressure regulation and transmits the fractional displacement signal x. m Sent to the displacement regulating electric drive module;

[0022] The present invention further includes a saturation stage, a condition judgment stage, and a zero-order holding stage in the hydraulic pressure open-loop adjustment module, wherein the hydraulic pressure open-loop adjustment module calculates the intermediate value x of the fractional displacement. mm Its formula is: The median value of the fractional displacement xmm After saturation limiting, the fractional displacement value x is obtained. m0 The signal is then sent to the conditional judgment stage, which checks whether the relative speed difference Δ is less than the set speed difference Δ0. If Δ ≤ Δ0, then x is output. m0 Otherwise, output the given displacement x. m1 The output of the conditional judgment stage is discretized by a zero-order hold stage and then used as the fractional displacement signal x. m Output.

[0023] The present invention further provides that the oil pressure closed-loop regulation module includes a discrete PI controller, a saturation stage, a condition judgment stage, and a zero-order hold stage, wherein the system oil pressure signal p and the set oil pressure p r The deviation is calculated using a discrete PI controller to determine the fractional displacement median value x. mm The formula is: In the formula, K pp K is the proportionality coefficient. ip T is the integral coefficient. sp2 The sampling time fractional displacement median value x of the discrete PI controller mm After saturation limiting, the fractional displacement value x is obtained. m0 The signal is then sent to the conditional judgment stage, which checks whether the relative speed difference Δ is less than the set speed difference Δ0. If Δ ≤ Δ0, then x is output. m0 Otherwise, output the given displacement x. m1 The output of the conditional judgment stage is discretized by a zero-order hold stage and then used as the fractional displacement signal x. m Output.

[0024] The present invention further provides that the formula for calculating the relative speed difference Δ is as follows:

[0025]

[0026] The present invention further specifies that the upper and lower limits of the saturation stage are 1 and the minimum fractional displacement of the hydraulic motor, respectively.

[0027] The present invention further specifies 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.

[0028] The present invention further provides that the given score displacement x m1 It is any value between the minimum fractional displacement of the hydraulic motor and 1.

[0029] The present invention further provides that the sampling time of the zero-order holding link must be greater than the adjustment time of the hydraulic motor displacement from the minimum value to the maximum value or from the maximum value to the minimum value.

[0030] The present invention further specifies that the sampling time of the discrete PI controller is ≤ the sampling time of the zero-order hold circuit, and is adjusted according to the requirements of calculation accuracy.

[0031] The present invention further provides that the generator vector controller includes a speed loop PI regulator, a current loop PI regulator, an SVPWM algorithm module, a Clark transformation module, a Park transformation module, and an inverse Park transformation module. The speed loop PI regulator adjusts the speed signal n and the set speed n according to the speed signal n and the set speed n. r Calculation of deviation given q-axis current signal The measured three-phase current values ​​i are sent to the current loop PI regulator, where Clark and Park transform the current. a i b i c Converted to i in two-phase stationary coordinate system α-β α i β And further converted to i in the synchronous rotating coordinate system dq d i q The signal is sent to the current loop PI controller, which sets the given d-axis current signal. And according to i d i q and Calculation of deviation for given voltage signal Then, the inverse Park transform will Transformed into α-β coordinates SVPWM algorithm based on The output PWM signal controls the three-phase PWM rectifier.

[0032] The beneficial effects of this invention are: 1. It can achieve decoupled control of rotational speed and system oil pressure under actual irregular wave sea conditions, and truly achieve constant speed and constant pressure control effect.

[0033] 2. Stable hydraulic pressure control of the system can be achieved through two forms: open-loop hydraulic pressure control and closed-loop hydraulic pressure control. The two forms can be configured individually or in combination according to the user's actual needs. Among them, the open-loop control structure is simple and does not require feedback of the system hydraulic pressure signal, which meets basic requirements. The closed-loop control structure has a better control effect. Attached Figure Description

[0034] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0035] Figure 1 This is a mechanical structure diagram of a buoyancy pendulum wave energy power generation device based on a constant-pressure hydraulic PTO.

[0036] Figure 2 This is a block diagram of a constant speed and constant pressure control structure for a wave energy power generation hydraulic PTO based on dual-parameter joint regulation.

[0037] Figure 3 This is a block diagram of the hydraulic open-loop regulating module.

[0038] Figure 4 This is a block diagram of the hydraulic closed-loop control module.

[0039] Figure 5 This is a block diagram of the generator vector controller.

[0040] Figure 6 This is the speed signal variation curve under constant speed and constant pressure control;

[0041] Figure 7 The curve showing the change in system oil pressure signal under constant speed and constant pressure control;

[0042] Figure 8 The actual operating curve of a constant-pressure hydraulic PTO with generator vector control and uncontrolled motor displacement;

[0043] Figure 9 The actual operating curve of a constant-pressure hydraulic PTO under constant speed and pressure control and open-loop oil pressure regulation;

[0044] Figure 10 This is the actual operating curve of a constant-pressure hydraulic PTO under constant speed and pressure control and closed-loop oil pressure regulation; Appendix labels: 1-buoyancy pendulum body; 2-guide rod assembly; 3-rack; 4-gear; 5-main shaft; 6-1-hydraulic cylinder one; 6-2-hydraulic cylinder two; 7-1-check valve one; 7-2-check valve two; 7-3-check valve three; 7-4-check valve four; 8-high-pressure accumulator; 9-speed control valve; 10-variable displacement hydraulic motor; 11-three-phase permanent magnet synchronous generator; 12-relief valve; 13-low-pressure oil tank; 14-pressure transmitter; 15-speed and torque meter; 16-Three-phase PWM rectifier; 17-DC bus; 18-Displacement regulation electric drive module; 19-Open-loop / closed-loop mode switching switch; 20-Hydraulic pressure open-loop regulation module; 21-Hydraulic pressure closed-loop regulation module; 22-Generator vector controller; 23-Main oil circuit; 24-1-Saturation circuit; 24-2-Saturation circuit; 25-1-Condition judgment circuit; 25-2-Condition judgment circuit; 26-1-Zero-order hold circuit; 26-2-Zero-order hold circuit; 27-Discrete PI regulator; 28-Speed ​​loop PI regulator; 29-Current loop PI regulator. Detailed Implementation

[0045] The following will describe in detail the implementation of this application with reference to the accompanying drawings and embodiments, so that the implementation process of how this application uses technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly.

[0046] Through CPHPTO irregular wave simulation research, the inventors discovered 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.

[0047] This invention does not consider the constant speed and constant pressure control strategy described in the invention patent "Method for Obtaining Comprehensive Characteristic Curves of Hydraulic PTO System Based on Wave Power Generation" which uses generator vector control to stabilize oil pressure and motor displacement control to stabilize speed. The reason is that the physical limitations of the maximum and minimum displacement of the motor limit the ability to stabilize the speed of the motor displacement control under large flow rate variations, and indirectly controlling the oil pressure through vector control can easily lead to the motor reversing and pumping oil.

[0048] Therefore, the following technical solution is proposed:

[0049] This invention relates to a constant speed and constant pressure control method for wave energy power generation hydraulic PTO based on dual-parameter joint regulation, specifically for wave energy power generation devices employing a constant pressure hydraulic PTO structure.

[0050] Example Examination Figure 1The illustrated buoyancy pendulum wave energy generation device based on a constant-pressure hydraulic PTO includes the following mechanical structure: a buoyancy 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; an overflow valve 12; a low-pressure oil tank 13; and a main oil circuit 23. The buoyancy pendulum body 1 is mounted on the main shaft 5 and can rotate relative to the main shaft. The cylinder bodies of hydraulic cylinder 1 (6-1) and hydraulic cylinder 2 (6-2), check valves 1 (7-1), 2 (7-2), 3 (7-3), 4 (7-4), high-pressure accumulator 8, speed control valve 9, variable displacement hydraulic motor 10, three-phase permanent magnet synchronous generator 11, overflow valve 12, low-pressure oil tank 13, pressure transmitter 14, speed and torque meter 15, and main oil circuit 23 are all fixed to the inner wall of the buoyancy pendulum body 1. Gear 4 is fixed on the main shaft 5 and meshes with rack 3. A rib is welded to the middle of the back of rack 3, and the two sides of the rib are fixedly connected to the piston rods of hydraulic cylinder 1 (6-1) and hydraulic cylinder 2 (6-2), respectively. The guide rod assembly 2 consists of upper and lower guide rods, and both ends of the guide rods are fixedly connected to the cylinder bodies of hydraulic cylinder 1 (6-1) and hydraulic cylinder 2 (6-2), respectively. The rack 3 has a through hole in its rib, through which the guide rod assembly 2 passes, forming a sliding pair with the rack 3 via a linear bearing. The oil port of hydraulic cylinder 1 (6-1) is connected to the inlet of check valve 1 (7-1) and the outlet of check valve 3 (7-3). The oil port of hydraulic cylinder 2 (6-2) is connected to the inlet of check valve 2 (7-2) and the outlet of check valve 4 (7-4). The outlets of check valve 1 (7-1) and check valve 2 (7-2) are connected to the inlet of main oil circuit 23, and the inlets of check valve 3 (7-3) and check valve 4 (7-4) are connected to the outlet of main oil circuit 23. A branch oil circuit also branches off from the inlet of main oil circuit 23, connecting to the inlet of relief valve 12. The outlet of relief valve 12 is connected to the low-pressure oil tank 13. A further branch oil circuit also branches off from the outlet of main oil circuit 23, connecting to the low-pressure oil tank 13. A high-pressure accumulator 8, a speed control valve 9, a pressure transmitter 14, and a variable displacement hydraulic motor 10 are installed sequentially between the inlet and outlet ports of the main oil circuit 23. The output shaft of the variable displacement hydraulic motor 10 and the input shaft of the speed and torque meter 15, as well as the output shaft of the speed and torque meter 15 and the input shaft of the three-phase permanent magnet synchronous generator 11, are all connected by couplings.

[0051] The working principle of the buoyancy pendulum wave energy generation device based on constant pressure hydraulic PTO is as follows: The buoyancy pendulum body 1 is completely submerged in seawater and stands upright on the main shaft 5 under the action of buoyancy torque. When the incident wave acts on the front of the buoyancy pendulum body 1, the buoyancy pendulum body 1 swings around the main shaft 5. The swing of the buoyancy pendulum body 1 relative to the main shaft 5 is converted into the translation of the rack 3 relative to the guide rod assembly 2 through the meshing gear 4 and rack 3. The rack 3 further pushes the piston rods of hydraulic cylinder 6-1 and hydraulic cylinder 6-2 relative to the cylinder body through the back rib, causing the oil chamber to expand to draw in oil or compress the oil chamber to generate high-pressure oil. When the rack 3 rib pushes the piston rod of hydraulic cylinder 6-2 to compress the oil chamber of hydraulic cylinder 6-2, the generated high-pressure oil enters the inlet of the main oil circuit 23 through check valve 7-1, and then passes sequentially through the high-pressure accumulator 8, speed control valve 9, pressure transmitter 14, and variable displacement hydraulic motor 10 to reach the outlet of the main oil circuit 23. Finally, it enters the oil chamber of hydraulic cylinder 6-1 through check valve 7-4. Similarly, when the rack 3 rib pushes the piston rod of hydraulic cylinder 6-1 to compress the oil chamber of hydraulic cylinder 6-1, the generated high-pressure oil enters the inlet of the main oil circuit 23 through check valve 7-2, and then passes sequentially through the high-pressure accumulator 8, speed control valve 9, pressure transmitter 14, and variable displacement hydraulic motor 10 to reach the outlet of the main oil circuit 23. Finally, it enters the oil chamber of hydraulic cylinder 6-2 through check valve 7-3. The four check valves act as flow correctors, converting the bidirectional flow of high-pressure oil into a unidirectional flow on the main oil circuit 23. The relief valve 12 is used to prevent overpressure in the constant-pressure hydraulic PTO. It opens to relieve pressure 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, thereby stabilizing the flow rate of the main oil circuit 23. The speed regulating valve 9 is used to regulate the flow rate of the main oil circuit 23 and participates in the power generation control. At the same time, when the flow rate of the main oil circuit 23 reaches the upper limit of the flow rate, the flow rate can be limited by the speed regulating valve 9 to avoid excessive speed of the three-phase permanent magnet synchronous generator 11. 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.

[0052] The constant speed and constant pressure control structure of a constant pressure hydraulic PTO is as follows: Figure 2As shown, the system includes a pressure transmitter 14 and a speed and torque meter 15 for signal acquisition; a three-phase PWM rectifier 16, a DC bus 17, and a generator vector controller 22 for generator vector control; and a displacement regulating electric drive module 18, an open-loop / closed-loop mode switch 19, an open-loop hydraulic pressure regulating module 20, and a closed-loop hydraulic pressure regulating module 21 for motor displacement control. The pressure transmitter 14 is installed between the outlet of the speed control valve 9 and the inlet of the variable displacement hydraulic motor 10, acquiring the system hydraulic pressure signal p from the main oil circuit 23 and transmitting it to the closed-loop hydraulic pressure regulating 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, measuring 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 control module 20, and a branch of the speed signal n is sent to the generator vector controller 22. The oil pressure p is set. r The hydraulic pressure is fed into two separate circuits: one to the open-loop hydraulic pressure regulating module 20 and the other to the closed-loop hydraulic pressure regulating module 21. The set speed n is... r The signal is sent in three paths to the open-loop hydraulic pressure control module 20, the closed-loop hydraulic pressure control module 21, and the generator vector controller 22. The open-loop hydraulic pressure control module 20 and the closed-loop hydraulic pressure control module 21 calculate the fractional displacement signal x. m Then, the signal is sent to the displacement adjustment electric drive module 18 via the open-loop / closed-loop mode switching switch 19. The displacement adjustment electric drive module 18 then adjusts the displacement according to the fractional displacement signal x. m The magnitude of the control current is linearly adjusted and sent to the solenoid valve of the variable displacement hydraulic motor 10 to control the motor displacement. The open-loop / closed-loop mode switch 19 is used to switch between open-loop and closed-loop hydraulic pressure regulation according to user needs. The generator vector controller 22 acquires the three-phase current signal i from the outlet of the three-phase permanent magnet synchronous generator 11. a i b i c It outputs an SVPWM signal to the three-phase PWM rectifier 16, which controls the electromagnetic torque of the three-phase permanent magnet synchronous generator 11, thereby indirectly regulating the speed n.

[0053] The internal structure of the hydraulic open-loop regulating module 20 is as follows: Figure 3 As shown. The median fractional displacement x is calculated according to equation (1). mm :

[0054]

[0055] In equation (1), D m This indicates the maximum displacement of the hydraulic motor provided by the equipment manufacturer. This indicates the set mechanical efficiency of the hydraulic motor. The midpoint of the fractional displacement x mm After the saturation stage 24-1 limiting, the fractional displacement calculation value x is obtained. m0The signal is then sent to conditional judgment step 25-1. Conditional judgment step 25-1 checks whether the relative speed difference Δ is less than the set speed difference Δ0. If Δ ≤ Δ0, then x is output. m0 Otherwise, output the given displacement x. m1 The output of conditional judgment step 25-1 is discretized by zero-order hold step 26-1 and used as the fractional displacement signal x. m Output.

[0056] The internal structure of the hydraulic 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 the discrete PI controller 27 to obtain the fractional displacement median value x. mm The formula is: In the formula, K pp K is the proportionality coefficient. ip T is the integral coefficient. sp2 The sampling time is for the discrete PI controller. The fractional displacement median value x. mm After the saturation stage 24-2 limiting, the fractional displacement calculation value x is obtained. m0 The signal is then sent to conditional judgment step 25-2. Conditional judgment step 25-2 checks whether the relative speed difference Δ is less than the set speed difference Δ0. If Δ ≤ Δ0, then x is output. m0 Otherwise, output the given displacement x. m1 The output of conditional judgment step 25-2 is discretized by zero-order hold step 26-2 and used as the fractional displacement signal x. m Output.

[0057] The hydraulic motor is set to a mechanical efficiency. It is related to the energy characteristics of the hydraulic motor, and can generally be taken as 0.9 or higher.

[0058] The upper and lower limits of the saturation links 24-1 and 24-2 are 1 and the minimum fractional displacement of the hydraulic motor, respectively.

[0059] The relative speed difference Δ is calculated according to equation (2):

[0060]

[0061] 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 speed n, in order to avoid the output values ​​of condition judgment circuit 1#25-1 and condition judgment circuit 2#25-2 being in x under the condition of speed n disturbance. m0 and x m1 Switching back and forth between these parameters affects the stability of constant speed and constant pressure control; a value of 0.05 is generally acceptable.

[0062] The given fractional displacement xm1 It can be any value between the minimum fractional displacement of the hydraulic motor provided by the equipment manufacturer and 1.

[0063] The sampling time of the zero-order hold circuit 26-1 and the zero-order hold circuit 26-2 must be greater than the adjustment time of the hydraulic motor displacement from the minimum to the maximum value or from the maximum value to the minimum value, generally greater than 0.05s, to avoid the actual displacement adjustment speed failing to keep up with the fractional displacement signal x. m The situation regarding the rate of change.

[0064] The sampling time of the discrete PI controller 27 is generally less than or equal to the sampling time of the zero-order hold circuit 26-1 and the zero-order hold circuit 26-2, and can be adjusted according to the requirements of calculation accuracy.

[0065] The internal structure of the generator vector controller is as follows: Figure 5 As shown, it includes a speed loop PI regulator 28, a current loop PI regulator 29, an SVPWM algorithm, Clark transformation, Park transformation, and inverse Park transformation. First, the speed loop PI regulator 28 calculates the speed signal n and the set speed n. r Calculation of deviation given q-axis current signal The measured three-phase current values ​​i are sent to the current loop PI regulator 29. Next, the Clark and Park transforms the measured three-phase current values ​​i a i b i c Converted to i in two-phase stationary coordinate system α-β α i β And further converted to i in the synchronous rotating coordinate system dq d i q The signal is sent to the current loop PI controller 29. Next, the current loop PI controller 29 sets the given d-axis current signal. And according to i d i q and Calculation of deviation for given voltage signal Then, the inverse Park transform will Transformed into α-β coordinates Finally, the SVPWM algorithm is based on The output PWM signal controls the three-phase PWM rectifier 16.

[0066] The proposed constant speed and pressure control method for wave energy generation hydraulic PTO based on dual-parameter joint tuning exhibits excellent speed and pressure stability. The control effect is illustrated below through simulation comparisons of irregular wave sea conditions; key parameter settings are shown in Table 1.

[0067] Table 1 Key Parameter Settings

[0068]

[0069] Simulation results are as follows Figures 6 to 10 As shown. Among them, Figure 6 and Figure 7 These are the speed signal variation curves and system oil pressure signal variation curves under constant speed and constant pressure control, respectively. Figure 6 and Figure 7 It can be seen that the constant speed and pressure control of wave energy power generation hydraulic PTO based on dual-parameter joint regulation can stabilize the speed signal at the set speed n. r Near the target location, stabilize the system oil pressure signal at the set oil pressure p. r In the vicinity, the performance of the closed-loop oil pressure regulation module is better than that of the open-loop oil pressure 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 a constant-pressure hydraulic PTO are plotted on the flow rate q-output N plane, representing generator vector control without motor displacement control, constant speed and pressure control with open-loop hydraulic pressure regulation, and constant speed and pressure control with closed-loop hydraulic pressure regulation, respectively. It should be noted that... Figures 8 to 10 The actual operating speed signal n is basically stable at the set speed n. r Nearby, and with an error of less than ±1%. Figures 8 to 10 In addition to the actual operating curve of the constant pressure hydraulic PTO, there is also the 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 straight line D = D) m The minimum displacement line (i.e., the straight line D = 0.3D) m ), the high-voltage accumulator charging pressure line (i.e., the straight line p = 0.8p) r ) and the output limit line (i.e., the straight line p = p) r and the line N = N r The curve is a broken line, where the area enclosed by the high-pressure accumulator charging pressure line, the maximum displacement line, and the minimum displacement line is the stable operating region. The area traversed by the output limit line is the high-efficiency and stable region of the constant-pressure hydraulic PTO. Therefore, the actual operating curve of the ideal constant-pressure hydraulic PTO must run along the output limit line. Under generator vector control and uncontrolled motor displacement, the actual operating curve of the constant-pressure hydraulic PTO does not coincide with the output limit line at all, and the period of operation in the unstable operating region is long, making it difficult to guarantee the economy and safety of the constant-pressure hydraulic PTO. Under constant-speed and constant-pressure control with open-loop oil pressure regulation and 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 it operates in the stable operating region for most of the time, ensuring the economy and safety of the constant-pressure hydraulic PTO. The regulation effect of constant-speed and constant-pressure control with closed-loop oil pressure regulation is better, and the degree of coincidence with the output limit line is higher.

[0070] The specification and claims use certain terms to refer to specific components. Those skilled in the art will understand that hardware manufacturers may use different names to refer to the same component. This specification and claims do not distinguish components based on differences in name, but rather on differences in function. The term "comprising" throughout the specification and claims is an open-ended term and should be interpreted as "comprising but not limited to." "Approximately" means that within an acceptable margin of error, those skilled in the art can solve the technical problem and substantially achieve the technical effect within a certain margin of error.

[0071] It should be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a product or system comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a product or system. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the product or system that includes said element.

[0072] The foregoing description illustrates 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. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the inventive concept described herein through the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A wave energy power generation hydraulic PTO constant speed and constant pressure control system based on dual-parameter joint regulation, characterized in that: include: The pressure transmitter is used to acquire the system oil pressure signal p of the main oil circuit and send the oil pressure signal p to the oil pressure closed-loop regulation module; A speed-torque meter is used to measure the torque signal Mg and speed signal n of the input shaft of a three-phase permanent magnet synchronous generator, and to convert the signal Mg into a torque meter. g The signal n is sent to the open-loop hydraulic control module, and then to the closed-loop hydraulic control module and the generator vector controller. A three-phase PWM rectifier controls the electromagnetic torque of a three-phase permanent magnet synchronous generator, indirectly regulating the speed n. The generator vector controller acquires the three-phase current signal i from the output of the three-phase permanent magnet synchronous generator. a i b i c It outputs an SVPWM signal to a three-phase PWM rectifier, and simultaneously receives the speed signal n and the set speed n. r ; The hydraulic pressure open-loop regulating module obtains the set hydraulic pressure p. r Set the rotation speed n r Speed ​​signal n and torque signal M g Given fractional displacement x m1 And calculate the fractional displacement signal x m ; The hydraulic pressure closed-loop control module obtains the set hydraulic pressure p. r Set the rotation speed n r Speed ​​signal n and oil pressure signal p, given fractional displacement x m1 And calculate the fractional displacement signal x m ; Displacement regulation electric drive module, based on fractional displacement signal x m The magnitude of the control current is linearly adjusted and sent to the solenoid valve of the variable displacement hydraulic motor to control the motor displacement. The open-loop / closed-loop mode switch toggles between open-loop and closed-loop hydraulic pressure regulation and transmits the fractional displacement signal x. m It is sent to the displacement regulating electric drive module.

2. The wave energy power generation hydraulic PTO constant speed and pressure control system based on dual-parameter joint regulation as described in claim 1, characterized in that, The open-loop hydraulic pressure control module includes a saturation stage, a condition judgment stage, and a zero-order holding stage. The open-loop hydraulic pressure control module calculates the fractional displacement median value x. mm Its formula is: ; the median value of the fractional displacement x mm After saturation limiting, the fractional displacement value x is obtained. m0 The data is then sent to the conditional judgment stage, which checks whether the relative speed difference Δ is less than the set speed difference Δ0. If Δ ≤ Δ0, then the output is... Otherwise, output the given displacement x. m1 The output of the conditional judgment stage is discretized by a zero-order hold stage and then used as the fractional displacement signal x. m Output.

3. The wave energy power generation hydraulic PTO constant speed and pressure control system based on dual-parameter joint regulation as described in claim 1, characterized in that, The hydraulic pressure closed-loop control module includes a discrete PI controller, a saturation circuit, a condition judgment circuit, and a zero-order hold circuit. The system hydraulic pressure signal p and the set hydraulic pressure p0 are also considered. r The deviation is calculated using a discrete PI controller to determine the fractional displacement median value x. mm The formula is: In the formula, This is the proportionality coefficient. The integral coefficient is... The sampling time of the discrete PI controller, and the median value of the fractional displacement x. mm After saturation limiting, the fractional displacement value x is obtained. m0 The signal is then sent to the conditional judgment stage, which checks whether the relative speed difference Δ is less than the set speed difference Δ0. If Δ ≤ Δ0, then x is output. m0 Otherwise, output the given displacement x. m1 The output of the conditional judgment stage is discretized by a zero-order hold stage and then used as the fractional displacement signal x. m Output.

4. A wave energy power generation hydraulic PTO constant speed and constant pressure control system based on dual-parameter joint regulation as described in claim 2 or 3, characterized in that, The formula for calculating the relative speed difference Δ is as follows: 。 5. A wave energy power generation hydraulic PTO constant speed and constant pressure control system based on dual-parameter joint regulation as described in claim 2 or 3, characterized in that, The upper and lower limits of the saturation stage are 1 and the minimum fractional displacement of the hydraulic motor, respectively.

6. A wave energy power generation hydraulic PTO constant speed and pressure control system based on dual-parameter joint regulation as described in 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 system based on dual-parameter joint regulation as described in claim 2 or 3, characterized in that, The given fractional displacement x m1 It is 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 system based on dual-parameter joint regulation as described in claim 2 or 3, characterized in that, The sampling time of the zero-order holding circuit must be greater than the adjustment time of the hydraulic motor displacement from minimum to maximum or from maximum to minimum.

9. A wave energy power generation hydraulic PTO constant speed and pressure control system based on dual-parameter joint regulation as described in claim 3, characterized in that, The sampling time of the discrete PI controller is less than or equal to the sampling time of the zero-order hold circuit, and is adjusted according to the required computational accuracy.

10. A wave energy power generation hydraulic PTO constant speed and pressure control system based on dual-parameter joint regulation as described in claim 1, characterized in that, The generator vector controller includes a speed loop PI regulator, a current loop PI regulator, an SVPWM algorithm module, a Clark transformation module, a Park transformation module, and an inverse Park transformation module. The speed loop PI regulator operates based on the speed signal n and the set speed n. r Calculation of deviation given q-axis current signal The measured three-phase current values ​​are sent to the current loop PI regulator, where Clark and Park transform the circuit. Convert to a two-phase stationary coordinate system Below And further converted into a synchronous rotating coordinate system. Below The signal is sent to the current loop PI controller, which sets the given d-axis current signal. and according to and Calculation of deviation for given voltage signal Then, the inverse Park transform will Transform into coordinates The SVPWM algorithm is based on The output PWM signal controls the three-phase PWM rectifier.

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