Introduction: The three-phase output of the generator is connected to the wind-solar hybrid controller, through which a stable voltage of 48V can be obtained and the stable electric energy can be stored in the storage battery. Let's briefly talk about the optimal design of the generator of the wave power plant, hoping to help you.
This article was developed by Shanghai Ocean University? Wave-current integrated power generation device? On the basis of, the generator is optimized, and the intermediate conversion device between the generator and the turbine is removed, which meets the form of direct drive power generation by ocean energy. The feasibility is verified by the performance test in the motor laboratory, which improves the efficiency and reliability of power generation and reduces the maintenance cost, and can be applied to practical production.
Wave-current integration; Power generation device; Generator; Optimize the design; Direct drive power generation
Preface of 0
Developed by Shanghai Ocean University? Wave-current integrated power generation device? At the same time, it can capture the forward thrust of waves and currents, and generate inertia and continuous rotation after receiving ocean energy; The main shaft drives the generator to rotate to generate electric energy. Provide stable electric energy for ocean observation, island reef life, mariculture and seawater desalination. It is used to solve the power supply demand in the ecological construction of national defense facilities in remote sea areas, inhabited islands not covered by some power grids and remote uninhabited islands. In this paper, the generator is taken as the research object, and its turbine matching generator is optimized, which overcomes the shortcoming that the traditional ocean energy needs to be converted in three parts, and reduces the transmission loss because there is no gearbox. By adopting the generator output voltage stability controller, the output speed of the impeller is stabilized, the power generation efficiency is improved, and the operation and maintenance cost is reduced. Especially in low-speed environment, the effect is more obvious.
The research object and method of 1
The generator designed in this project meets the requirements of direct-drive power generation by ocean energy. However, the existence of gearbox has become one of the factors that restrict the development of marine energy generating units: the gearbox has been rotating at high speed during the operation of the unit, which increases the system loss and reduces the energy utilization rate; The marine energy generating set is often installed at sea level or seawater, which is subjected to severe cold and heat, seawater corrosion, great temperature change and harsh environmental conditions, resulting in harsh working conditions and heavy maintenance workload of the speed-increasing gearbox; In order to adapt to the harsh operating environment, the gearbox is expensive after all, and because of the changeable ocean energy, it often causes overload, which is more likely to damage the gearbox and increase the operating cost of the system.
Therefore, this design eliminates the intermediate conversion link, and the right end of the main shaft of the hydraulic turbine is connected with the motor through the coupling, which directly drives the motor to generate electricity, and there is no link in the middle, thus realizing absolute direct drive. The direct-drive power generation mode developed in this paper has the following advantages:
(1) Improve power generation efficiency. There is no gearbox in direct-drive power generation, which reduces transmission loss and improves power generation efficiency, especially in low-speed environment.
(2) The reliability is improved. The direct drive technology saves the gearbox and its accessories, simplifies the transmission structure and improves the reliability of the unit. At the same time, the unit runs at low speed, with few rotating parts and high reliability.
(3) Low operation and maintenance cost. Adopting gearless direct drive technology can reduce the number of generator parts, avoid changing gearbox oil regularly and reduce operation and maintenance costs.
However, such a direct-drive power generation mode of ocean energy requires the generator to have the characteristics of low-speed operation and high efficiency, and even more requires the generator to be able to operate in seawater.
Design of direct-drive generator
2. 1 structural design of direct-drive generator
The generator adopts disk structure: the energy carried by wave energy per unit volume is limited. In order to collect these energies efficiently, the generator becomes one of the key devices for energy conversion in the device. Wave energy generator, at most hundreds of revolutions per minute, so the technical index and economy of the generator determine the competitiveness of this equipment in the market. There are two kinds of generators in common use: the air gap magnetic field of cylindrical generators is distributed along the axial direction. In order to obtain high power generation efficiency, the cylindrical generator must run at high speed, while the stator and rotor of the disk generator are in parallel structure, which overcomes the structural shortcomings of the cylindrical generator, has small axial size, no lamination riveting process and good manufacturability, so the disk generator can run at low speed. Therefore, the generator adopts the disk generator structure, which can reach the rated power at low speed, meet the technical requirements of wave power generation system for generators, and improve the efficiency.
2.2 Design of generator output voltage stability controller
The three-phase output of the generator is connected to the wind-solar hybrid controller, and the stable voltage of 48V can be obtained through the wind-solar hybrid controller, and the stable electric energy can be stored in the storage battery. The principle of the controller is to convert the input AC current into DC current through a three-phase bridge full-control rectifier circuit, and the DC current controls the voltage output at 48V through a buck-boost chopper circuit. It is worth noting that when the generator speed reaches 54r/min, there will be current output at the output end of the controller. Controller As shown in Figure 2, the current flowing through the controller is DC, which is connected to the battery pack behind the controller. +-? Just connect the interface of the battery, and the reverse details are shown in Figure 3.
2.3 working principle of direct drive
2.3. 1 three-phase bridge full-control rectifier circuit
In the three-phase bridge full-control rectifier circuit, as shown in Figure 4, thyristors KP 1 and KP4 are connected to phase A, thyristors KP3 and KP6 are connected to phase B, and transistors KP5 and KP2 are connected to phase C. Thyristors KP 1, KP3 and KP5 form a cathode group, while thyristors KP2, KP4 and KP6 form an anode group.
2.3.2 Principle of step-up and step-down chopper circuit
Fig. 5 shows the principle of boost and buck chopper circuits. When V is on, power supply E supplies power to L through V to store energy, and the current at this time is i 1. At the same time, C keeps the output voltage unchanged and supplies power to the load R. When V is turned off, the energy of L is released to the load, and the current is i2. The polarity of the load voltage is negative and positive, which is opposite to the polarity of the power supply voltage. This circuit is also called reverse polarity chopper circuit.
3 experimental analysis
In the laboratory, the number of revolutions of steam turbine under different working conditions is simulated, and the generator is driven by a controllable speed motor to test its power generation performance. Therefore, we built a generator test platform. As shown in Figure 7, the generator test platform is fixed with a frame and connected with a sensor through a coupling. In the generator test platform, on the right is a DC motor, which simulates the role of a water turbine as a power source. Connected to the motor through the coupling is a sensor, which can see the instantaneous torque, speed and power after being connected to the display screen. Power can be the input power of the generator, so we can get the efficiency of the generator after measuring the output power. The resistor box, rectifier and torque meter are shown in Figure 8. The three displays on the torque meter are torque, speed and power.
The generator sends out three-phase alternating current and inputs it into the electronic test platform. The transient voltage, current, power and power factor of three-phase alternating current can be obtained through the electronic test platform. The current from the rectifier is rectified into DC current, which flows into the power meter and connects the sliding rheostat box in series to the whole circuit.
4 motor scheme summary and prospect
The scheme adopts direct drive power generation mode, which not only improves the power generation efficiency, but also improves the reliability of the power generation device and meets the requirements of barrier-free operation time. The generator adopts disk generator structure, which can reach the rated power at low speed, meeting the technical requirements of wave power generation system for generators and improving efficiency. After the three-phase alternating current generated by the device passes through the controller, the measured voltage is basically maintained at about 48V, which is a direct current, providing conditions for the storage battery to store electric energy, and finally meeting our requirements.
However, when the generator set is installed at sea level or in seawater, it is vulnerable to seawater corrosion due to severe cold and heat, seawater corrosion, great temperature change and harsh environmental conditions. Therefore, the research directions that can be done in the future are as follows:
1) The generator itself should have a good mechanical seal design to evaluate the reliability of the seal system under different seawater depths and pressures. Under the condition of seawater circulation, the corrosion law of marine materials in different regional environments such as silt, deep sea, shallow sea, spray splashing and sea fog was studied, and the corresponding corrosion-resistant materials were designed.
2) A waterproof box can be added outside the generator, so that the generator has an isolation layer from seawater, which not only achieves the waterproof effect, but also makes the generator not need to be immersed in seawater.
refer to
You are Goya. Development Progress of Ocean Wave Energy in China [J]. Scientific and Technological Achievements of China, 2006 (2): 17- 19.
[2] Li. Marine energy development [M]. Ocean Press, 2008.
Sheng, You and Ma Yujiu. Hydrodynamic analysis and optimal design of a wave energy experimental device [J]. Ocean Engineering, 2006,24 (3):107-12.
[4], You, Wu Bijun, Li. China Ocean Energy Patent Research [J]. Renewable energy, 2007,25 (2): 79-81.
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