CN100571016C - A variable speed and constant frequency method and device for ocean current power generation based on hydraulic transmission - Google Patents

Abstract

The invention discloses a variable-speed and constant-frequency method and device for ocean current power generation based on hydraulic transmission. Connect the main shaft of the impeller to the variable pump, the high pressure oil output by the variable pump is connected to the accumulator and the variable motor, the permanent magnet synchronous generator is connected to the variable motor and then connected to the power grid; the speed sensors are respectively installed on the main shaft of the impeller and the main shaft of the generator to control The controller calculates the displacement signal of the variable pump according to the speed of the impeller and the velocity of the sea current and outputs it, and adjusts the displacement of the variable pump to change the reaction torque on the main shaft of the variable pump, thereby changing the speed of the impeller to achieve variable speed operation. The controller calculates and outputs the displacement signal of the variable motor according to the rotational speed and rated rotational speed of the generator, and adjusts the displacement of the variable motor to keep the rotational speed of the variable motor constant, so that the generator can generate electric energy at the rated frequency to realize constant frequency operation. The invention makes the variable-speed operation and energy output of the ocean current power generation device more stable, is less affected by the impact of the ocean current, has no current conversion equipment, and has higher efficiency.

Description

A variable speed and constant frequency method and device for ocean current power generation based on hydraulic transmission

technical field

The invention relates to a speed-variable and constant-frequency method of a power generation system and a device thereof, in particular to a hydraulic transmission-based ocean current power generation variable-speed and constant-frequency method and a device thereof.

Background technique

The horizontal axis ocean current power generation device is a new type of ocean current energy development and utilization device that entered the research field at the beginning of the 21st century. It is based on Bezier's energy capture theory, which captures the kinetic energy of water through the impeller and converts it into electrical energy. Similar to wind power, when the speed of the impeller changes with the speed of the water flow, it can make the impeller capture more energy of the ocean current. When the generator in the ocean current power generation device is connected in parallel with the power grid, the generator is required to generate electric energy with a constant frequency, that is, to operate at a constant frequency. At present, the energy transmission mode of the horizontal-axis current power generation devices designed in the world is mechanical transmission, that is, the impeller drives the generator to rotate through the gearbox to generate electricity, and the transmission ratio of the gearbox is fixed. The variable speed and constant frequency operation of the ocean current power generation device can use the variable speed and constant frequency method in the field of wind power generation, and there are mainly two types. One method is to use a doubly-fed asynchronous generator that supports variable speed operation. By controlling the generator to make the impeller run at variable speed, the generator also operates with the variable speed of the impeller. When the generator speed changes, the rotor side of the doubly-fed asynchronous generator The adjustment of the frequency conversion device makes the frequency of the electric energy sent by the generator constant. Another method is to use an ordinary synchronous generator, connect a rectifier inverter controller between the generator and the power grid, and make the impeller run at variable speed through the adjustment of the rectifier inverter controller, and at the same time make the generator running at variable speed emit constant frequency Electric energy is then fed into the grid. Both of the above two variable speed and constant frequency methods are based on electrical methods, and both require expensive inverter equipment, which will cause more than 15% energy loss during the energy transfer process. In the horizontal axis type ocean current power generation device, if the electric variable speed and constant frequency method is adopted, since the generator is driven by the impeller to generate electricity after the gear box speeds up, the generator is greatly affected by the impact of the ocean current, and the variable speed of the impeller The energy output of operation and sea current power generation device is more unstable. In addition, its expensive generators have to be placed underwater, which makes maintenance inconvenient. The use of inverter equipment not only causes energy loss, but also makes the structure of the power generation system huge and complicated, especially the electrical system.

Contents of the invention

The purpose of the present invention is to provide a hydraulic transmission-based ocean current power generation variable speed constant frequency method and its device, which uses hydraulic transmission to convert energy, and adjusts the displacement of variable hydraulic pumps and variable hydraulic motors in the process of hydraulic energy transmission. To realize the variable speed and constant frequency operation of the ocean current power generation device, improve the energy capture rate of the ocean current power generation device, and make the variable speed operation and energy output of the ocean current power generation device more stable.

The technical solution adopted by the present invention to solve its technical problems is:

1. A variable speed and constant frequency method for ocean current power generation based on hydraulic transmission:

1) Input the mechanical energy of the impeller into the main shaft of the variable hydraulic pump, input the mechanical energy output by the variable hydraulic motor into the main shaft of the permanent magnet synchronous generator, and install speed sensors on the main shaft of the impeller and the main shaft of the permanent magnet synchronous generator respectively. A flow rate sensor is installed on the rotating plane, and the PLC controller storing the control program is electrically connected with the impeller speed sensor, the generator speed sensor, the flow rate sensor, the variable hydraulic pump and the variable hydraulic motor;

2) Use the flow velocity sensor and the impeller speed sensor to measure the flow velocity v of the sea current and the speed n _y of the impeller respectively, and input them to the PLC controller. The PLC controller calculates the impeller speed according to the flow velocity v of the sea current and the optimal tip speed ratio λ _opt of the impeller. Optimum rotational speed n _opt , and then according to the optimum rotational speed n _opt of the impeller and the rotational speed n _y of the impeller, the displacement control signal q _p of the variable hydraulic pump is calculated by its internal control algorithm and output, adjusted by the variable mechanism of the variable hydraulic pump Its displacement, and then change the reaction torque on the main shaft of the variable hydraulic pump, thereby changing the speed of the impeller, and realizing the variable speed operation of the impeller;

3) Use the generator speed sensor to measure the speed n _g of the permanent magnet synchronous generator, and input it to the PLC controller. The PLC controller calculates the variable hydraulic pressure based on the speed n _g and the rated speed n _gN of the permanent magnet synchronous generator by its internal control algorithm. The displacement control signal q _m of the motor is output, and its displacement is adjusted through the variable mechanism of the variable hydraulic motor, so that the speed of the variable hydraulic motor is constant at the rated speed n _gN of the permanent magnet synchronous generator, and then the permanent magnet synchronous generator Generate constant frequency electric energy to realize constant frequency operation of permanent magnet synchronous generator.

2. A variable speed and constant frequency device for ocean current power generation based on hydraulic transmission:

Connect the main shaft of the impeller to the main shaft of the variable hydraulic pump. The variable hydraulic pump is connected to the oil filter and the oil tank through the oil pipe. The outlet of the oil filter is connected to the safety valve. The high pressure oil output by the variable hydraulic pump is connected to the The accumulator and the variable hydraulic motor are installed, and a cut-off valve is installed at the entrance of the accumulator. The main shaft of the variable hydraulic motor is directly connected with the main shaft of the permanent magnet synchronous generator, and the permanent magnet synchronous generator is directly connected with the power grid; the PLC controller is connected with the power grid respectively. The impeller speed sensor, generator speed sensor, flow rate sensor, variable hydraulic pump and variable hydraulic motor are electrically connected.

The beneficial effect that the present invention has compared with background technology is:

1. Compared with the variable speed and constant frequency method based on the electric type, the variable speed and constant frequency method based on the hydraulic transmission makes the variable speed operation and energy output transmission of the ocean current power generation device more stable, and is less affected by the impact of the ocean current, especially suitable for the horizontal shaft type ocean current power generation device.

2. The displacement adjustment of the variable hydraulic pump and the variable hydraulic motor is used to realize the variable speed and constant frequency operation of the ocean current power generation device. It is simple and reliable, and the energy is less lost during the transmission process, so that the power generation system has higher efficiency.

3. The required device of the inventive method is simple, and the generator adopts a common permanent magnet synchronous generator, and can be placed on sea level, and its output electric energy can be directly incorporated into the power grid, eliminating the need for converter equipment, so that the ocean current power generation device The electrical system is simple and reliable.

Description of drawings

Fig. 1 is the hydraulic principle diagram of the present invention.

Figure 2 is a schematic diagram of the working principle of the PLC controller.

Fig. 3 is a relationship curve between the tip speed ratio of the impeller and the energy capture rate of the impeller.

In the figure: 1. impeller, 2. impeller speed sensor, 3. flow rate sensor, 4. variable hydraulic pump, 5. oil filter, 6. safety valve, 7. one-way valve, 8. stop valve, 9. energy storage Device, 10. Variable hydraulic motor, 11. Fuel tank, 12. Generator speed sensor, 13. Permanent magnet synchronous generator, 14. Power grid, 15. PLC controller

v - the sea current velocity signal output by the velocity sensor, λ _opt - the optimum tip speed ratio of the impeller

n _opt - the optimum rotational speed signal of the impeller, n _y - the impeller rotational speed signal output by the impeller rotational speed sensor

n _ye - the speed deviation signal of the impeller, q _p - the displacement control signal of the variable hydraulic pump

n _gN - the rated speed value of the permanent magnet synchronous generator, n _g - the generator speed signal output by the generator speed sensor

n _ge - the speed deviation signal of the generator, q _m - the displacement control signal of the variable hydraulic motor

C _P - the energy capture rate of the impeller, C _Pmax - the maximum energy capture rate of the impeller

λ - the tip speed ratio of the impeller

Detailed ways

The present invention will be further described below in conjunction with drawings and embodiments.

As shown in Figure 1 and Figure 2, the present invention connects the main shaft of the impeller 1 with the main shaft of the variable hydraulic pump 4, the variable hydraulic pump 4 is connected with the oil filter 5 and the oil tank 11 through the oil pipe, and the outlet of the oil filter 5 is connected with the safety valve 6. The high-pressure oil output by the variable hydraulic pump 4 is connected to the accumulator 9 and the variable hydraulic motor 10 through the oil filter 5 and the one-way valve 7. A cut-off valve 8 is installed at the entrance of the accumulator 9, and the main shaft of the variable hydraulic motor 10 Directly link to each other with the main shaft of permanent magnet synchronous generator 13, and permanent magnet synchronous generator 13 directly links to each other with power grid 14; On the main shaft of impeller 1 and the main shaft of permanent magnet synchronous generator 13, rotational speed sensor 2,12 are installed respectively, on the main shaft of impeller 1 A flow velocity sensor 3 is installed on the rotation plane, and the PLC controller 15 is electrically connected with the impeller velocity sensor 2, the generator velocity sensor 12, the flow velocity sensor 3, the variable hydraulic pump 4 and the variable hydraulic motor 10 respectively.

As shown in Fig. 1 and Fig. 2, the present invention uses flow velocity sensor 3 and impeller rotational speed sensor 2 to measure respectively the flow velocity v of ocean current and the rotational speed n _y of impeller 1, input PLC controller 15, PLC controller 15 according to the flow velocity v of ocean current and The optimal tip speed ratio λ _opt of the impeller calculates the optimal rotational speed n _opt of the impeller, and then calculates the displacement of the variable hydraulic pump 4 by its internal control algorithm based on the optimal rotational speed n _opt of the impeller and the rotational speed n _y of the impeller The control signal _qp is output, and the displacement of the variable hydraulic pump 4 is adjusted through the variable mechanism, thereby changing the counter torque on the main shaft of the variable hydraulic pump 4, thereby changing the speed of the impeller 1, and realizing the variable speed operation of the impeller 1.

Measure the rotational speed n _g of the permanent magnet synchronous generator 13 with the generator rotational speed sensor 12, and input it to the PLC controller 15, and the PLC controller 15 calculates by its internal control algorithm according to the rotational speed n _g and the rated rotational speed n _gN of the permanent magnet synchronous generator 13 Output the displacement control signal q _m of the variable hydraulic motor 10 and output it, adjust the displacement through the variable mechanism of the variable hydraulic motor 10, so that the speed of the variable hydraulic motor 10 is constant at the rated speed n _gN of the permanent magnet synchronous generator 13, Furthermore, the permanent magnet synchronous generator 13 can generate electric energy with a constant frequency, so as to realize the constant frequency operation of the permanent magnet synchronous generator 13 .

Principle of the present invention is as follows:

As shown in FIG. 1 , the impeller 1 of the horizontal axis type generates lift under the flow impact of the ocean current and rotates, captures the energy of the ocean current and converts it into mechanical energy. The impeller directly drives the variable hydraulic pump 4 to rotate, and inputs mechanical energy to the hydraulic transmission system. The variable hydraulic pump sucks low-pressure oil from the oil tank, and outputs hydraulic oil with a certain pressure and flow rate from its output port. The high-pressure oil output by the variable hydraulic pump 4 flows into the accumulator 9 through the oil filter 5 and the one-way valve 7 for storage, and partly flows into the variable hydraulic motor 10 to rotate the main shaft of the hydraulic motor, thereby directly driving the permanent magnet synchronous generator 13 to run. The hydraulic energy of the hydraulic transmission system is converted into mechanical energy, and the generator converts the mechanical energy into electrical energy and outputs it to the grid. The outlet of the oil filter 5 is connected in parallel with the safety valve 6 to limit the excessive pressure of the system. The one-way valve 7 at the outlet of the oil filter 5 can prevent the oil from the accumulator 9 and the hydraulic motor 10 from flowing to the hydraulic pump. The cut-off valve 8 installed at the inlet of the accumulator 9 can seal off the hydraulic fluid during system installation and maintenance.

The tip speed ratio of the impeller λ=2πn _y R/60v, where n _y is the rotational speed of the impeller, R is the radius of the impeller, and v is the velocity of the sea current. When the installation angle of the blade is fixed, there is a nonlinear relationship between the energy capture rate C _P of the impeller and the tip speed ratio λ of the impeller (the ratio of the linear velocity of the impeller tip to the velocity of the sea current), as shown in Figure 3 It shows that when the tip speed ratio λ is equal to the optimal tip speed ratio λ _opt , the energy capture rate C _P of the impeller can take the maximum value C _Pmax , at this time the impeller can capture the ocean current energy to the maximum. Therefore, when the flow velocity of the sea current changes below the rated flow velocity, changing the speed of the impeller to keep the impeller running at the optimum tip speed ratio λ _opt can keep the energy capture rate C _P of the impeller at the maximum, thereby maximizing the capture of sea current energy. When the flow velocity of the sea current changes above the rated flow velocity, it is hoped that the power captured by the impeller will not change with the change of the flow velocity, and the rated capture power will be maintained. At this time, the tip speed ratio λ can also be changed by adjusting the speed of the impeller to make the energy of the impeller The capture rate _Cp is varied so that the capture power of the impeller remains constant at the rated value.

As shown in Figures 1 and 2, speed sensors 2 and 12 are respectively installed on the main shaft of the impeller 1 and the main shaft of the permanent magnet synchronous generator 13, and a flow sensor 3 is installed on the rotation plane of the impeller 1, and a PLC for storing control programs is added controller 15. Use the velocity sensor to measure the flow velocity signal v of the sea current and input it to the PLC controller. The PLC controller calculates the optimum speed signal n _opt of the impeller according to the optimal blade tip speed ratio λ _opt of the impeller and the flow velocity signal v of the sea current. The optimal tip speed ratio _λopt is a constant stored in the PLC controller, and the calculation process is completed by the calculation program of the optimal impeller speed stored in the PLC controller. Use the impeller speed sensor to measure the speed n _y of the impeller and input it to the PLC controller. The PLC controller calculates the speed deviation signal n _ye of the impeller according to the optimal speed signal n _opt of the impeller and the speed n _y of the impeller, and then the internal The stored digital PID control algorithm calculates the displacement control signal q _p of the variable hydraulic pump, and outputs it from the PLC controller, and adjusts the displacement of the variable pump through the variable mechanism of the variable hydraulic pump. And the reaction torque T _p on the main shaft of the variable hydraulic pump = p _p q _p /2π, where p _p is the outlet pressure of the pump, which is determined by the load of the system, and the load of the system can be regarded as constant, and q _p is the variable hydraulic pump Therefore, adjusting the displacement q _p of the variable hydraulic pump can change the reaction torque T _p on the main shaft of the variable hydraulic pump, and then indirectly change the speed of the impeller to realize the variable speed operation of the impeller. The speed of the impeller controlled by adjusting the displacement of the hydraulic pump above only responds to the low-frequency component of the sea current velocity, and does not respond to the high-frequency component of the flow velocity. The energy fluctuation caused by the high-frequency component of the flow velocity is alleviated by the accumulator. When the flow rate increases in a short time, the accumulator stores the excess energy, and when the flow rate decreases, the accumulator releases the energy to make the power output reach the ideal state.

When the permanent magnet synchronous generator is connected in parallel with the grid, the frequency of the electric energy generated by the permanent magnet synchronous generator is required to be consistent with the frequency of the grid, which requires the synchronous generator to run at its rated speed. As shown in Figures 1 and 2, in the method of the present invention, the rotational speed n _g of the generator is measured by the generator rotational speed sensor, which is input to the PLC controller, and the PLC controller is based on the rated rotational speed value n _gN of the permanent magnet synchronous generator stored inside it. Calculate the generator speed deviation signal n _ge with the input generator speed n _g , and calculate the displacement control signal q _m of the variable hydraulic motor by the digital PID control algorithm stored in the PLC controller according to the deviation signal n _ge , and From the output of the PLC controller, the displacement of the variable hydraulic motor is adjusted through the variable mechanism of the variable hydraulic motor. And the speed of the variable hydraulic motor n _m =60Q _m η _V /q _m , where Q _m is the flow of oil flowing into the hydraulic motor, which changes with the power captured by the impeller, and η _V is the volumetric efficiency of the hydraulic motor, which can be seen is a constant, and q _m is the displacement of the hydraulic motor, so when the oil flow Q _m flowing into the hydraulic motor changes, the speed n _m of the variable hydraulic motor can be kept constant by adjusting the displacement q _m of the variable hydraulic motor, which is kept as The rated rotational speed value n _gN of the permanent magnet synchronous generator further enables the permanent magnet synchronous generator to generate electric energy with a constant frequency, and realizes the constant frequency operation of the permanent magnet synchronous generator.

Claims (2)

1, a kind of based on hydraulicdriven current power generation speed-changing constant frequency method, it is characterized in that:

1) with the main shaft of the mechanical energy input variable hydraulic pump of impeller, the hydraulic oil of volume adjustable hydraulic pump output is inserted accumulator and variable hydraulic motor through oil filter and unidirectional valve, thereby driving variable hydraulic motor rotates, again the mechanical energy of variable hydraulic motor output is imported the main shaft of magneto alternator, on the main shaft of the main shaft of impeller and magneto alternator, speed probe is installed respectively, on the rotational plane of impeller, flow sensor is installed, the PLC controller of storage control program respectively with the wheel speed transducer, the generator speed transducer, flow sensor, volume adjustable hydraulic pump and variable hydraulic motor are electrically connected;

2) measure the flow velocity v of ocean current and the rotation speed n of impeller respectively with flow sensor and wheel speed transducer _y, input PLC controller, the PLC controller is according to the flow velocity v of ocean current and the best tip speed ratio value λ of impeller _OptCalculate the optimum speed n of impeller _Opt, the best tip speed ratio value λ of impeller wherein _OptFor being stored in the constant in the PLC controller, then according to the optimum speed n of impeller _OptRotation speed n with impeller _yCalculate the discharge capacity control signal q of volume adjustable hydraulic pump by its inner control algolithm _pAnd output, regulate its discharge capacity by the stroking mechanism of volume adjustable hydraulic pump, and then change the reaction torque on the volume adjustable hydraulic pump main shaft, thereby change the rotating speed of impeller, realize the changed speed operation of impeller;

3) rotation speed n of usefulness generator speed sensor measurement magneto alternator _g, input PLC controller, the PLC controller is according to rotation speed n _gRated speed n with magneto alternator _GNGo out the discharge capacity control signal q of variable hydraulic motor by its internal control algorithm computation _mAnd output, regulate its discharge capacity by the stroking mechanism of variable hydraulic motor, thereby make the rated speed n of the invariablenes turning speed of variable hydraulic motor at magneto alternator _GN, and then make magneto alternator send the electric energy of constant frequency, realize the constant frequency running of magneto alternator.

2, be used for the described a kind of device of claim 1 based on hydraulicdriven current power generation speed-changing constant frequency method, it is characterized in that: the main shaft of impeller (1) and the main shaft of volume adjustable hydraulic pump (4) are linked to each other, volume adjustable hydraulic pump (4) is connected with fuel tank (11) with oil filter (5) by oil pipe, the outlet attachment security valve (6) of oil filter (5), the hydraulic oil of volume adjustable hydraulic pump (4) output inserts accumulator (9) and variable hydraulic motor (10) through oil filter (5) and unidirectional valve (7), inlet at accumulator (9) is installed break valve (8), the main shaft of variable hydraulic motor (10) directly links to each other with the main shaft of magneto alternator (13), and magneto alternator (13) directly links to each other with electrical network (14); PLC controller (15) is electrically connected with wheel speed transducer (2), generator speed transducer (12), flow sensor (3), volume adjustable hydraulic pump (4) and variable hydraulic motor (10) respectively.

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