Hydraulic generator set is also called“Turbine generator unit”。The power generation unit formed by the combination of each water turbine and the supporting generator in the hydropower station is the main power equipment for generating electric energy in the hydropower station.When the water flow quoted by the hydropower station passes through the hydraulic turbine, the water energy is converted into the mechanical energy that drives the machinery to rotate;The generator converts mechanical energy into electrical energy and outputs it.[1]
Chinese name
Hydroelectric generating set
Foreign name
Hydroelectric generator
Alias
Turbine generator unit
working principle
Convert potential energy of water into electric energy
The function of hydraulic generator set is toriver, lakes, etc. The water flow with potential energy at a high place will be converted into the mechanical energy of the water turbine through the water turbine, and the water turbine will drive the generator to generate electricity to convert the mechanical energy into electrical energy.
In hydroelectric generating setHydro generatorIt is driven by water turbine.The speed of the generator determines the frequency of the AC output, so stabilizing the speed of the rotor is essential to ensure the stability of the frequency.Can takeclosed-loop control The speed of the hydraulic turbine is controlled in the way of, that is, the frequency signal samples of the AC power sent out are fed back to the control system that controls the opening and closing angle of the guide vane of the hydraulic turbine to control the output power of the hydraulic turbine, so as to achieve the purpose of stabilizing the speed of the generator.
constitute
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Hydraulic generator set is an energy conversion device that converts potential energy of water into electric energy. It is generally composed of water turbine, generator, governor, excitation system, cooling system and power station control equipment.
(1) Water turbine: commonly usedWater turbineThere are two types: impact type and counterattack type.
(2) Generator: most generators adoptSynchronous generatorIts speed is low, generally below 750r/min, and some only have dozens of rpm;Due to low speed, there are many magnetic poles;Large structure size and weight;There are two types of installation of hydraulic generator sets: vertical and horizontal.
(3) Speed governing and control devices (including speed governor and oil pressure device): the role of the speed governor is to regulate the speed of the hydraulic turbine to ensure that the frequency of the output electric energy meets the power supply requirements, and to achieve unit operation (startup, shutdown, speed change, load increase and load decrease) and safe and economic operation.Therefore, the performance of the governor shall meet the requirements of rapid operation, sensitive response, rapid stability, convenient operation and maintenance. It also requires reliable manual operation and emergency shutdown devices.
(4) Excitation system: the hydraulic generator is generally electromagneticSynchronous generatorThrough the control of DC excitation system, the voltage regulation of electric energy, the regulation of active power and reactive power and other controls can be realized to improve the quality of output electric energy.
(5) Cooling system: air cooling is mainly used for the cooling of small hydraulic generator, and the ventilation system is used to cool the stator, rotor and iron core surface of the generator.However, with the increase of single unit capacity, the thermal loads of stator and rotor are constantly increasing. In order to increase the output power of generator per unit volume at a certain speed, the direct water cooling mode of stator and rotor windings is adopted for large capacity hydro generators;Or the stator winding is cooled by water, while the rotor is cooled by strong wind.
(6) Control equipment of the power station: the control equipment of the power station is mainly microcomputer based, realizing the functions of grid connection, voltage regulation, frequency modulation, power factor regulation, protection and communication of the hydraulic generator.
(7) Braking device: hydraulic generators with rated capacity exceeding a certain value are equipped with braking device, which is used to continuously brake the rotor when the speed drops to 30%~40% of the rated speed during generator shutdown to avoidthrust bearingThe bearing bush was burnt due to the oil film damage at low speed.Another function of the braking device is to jack up the rotating parts of the generator with high-pressure oil before installation, maintenance and starting.The braking device uses compressed air for braking.[2]
working principle
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The energy conversion process of the hydraulic generator set is divided into two stages: first, the potential energy lost by water is converted into mechanical energy by the hydraulic turbine, and then the mechanical energy of the hydraulic turbine is converted into electrical energy by the generator.The specific process is as follows: under the impact of water flow, the turbine starts to rotate and converts the potential energy of water into mechanical energy;The hydraulic turbine drives the generator connected in the same axis to rotate. Under the action of the excitation current, the rotating rotor drives the excitation field to rotate, and the stator winding of the generator cuts the excitation magnetic line of force in itInduced electromotive forceAt the same time of outputting electric energy, an electromagnetic braking torque opposite to its rotation direction will be generated on the rotor.Since the water flow acts on the turbine uninterruptedly, the rotating torque obtained by the turbine from the water flow is used to overcomeMotor rotorWhen the two torques reach balance, the hydraulic generator set will run at a constant speed to stably generate power and realize energy conversion.Therefore, the hydraulic turbine and generator are the most critical two components in the hydraulic generator set.[2]
control technology
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Hydroelectric generating setautomatic control systemTasks undertaken include: automatic paralleling of hydroelectric generating units, automatic regulation of excitation, frequency and active power, compensation of reactive power, automatic control of auxiliary machines, automatic operation and automatic protection of hydroelectric generating units, among which frequency and power control are the main ones.
Small hydroelectric generating units convert water energy into electric energy to supply load directly or connect to power grid for load use.For the load, not only the power supply is required to be safe and reliable, but also the power supply quality is required to be high, that is, the voltage and frequency of the electric energy should be rated with small fluctuations.
The stability of the voltage, frequency or grid connected voltage and frequency generated by the generator depends on the balance of reactive power and active power in the generator or grid, respectively.The reason for frequency fluctuation is the imbalance between the input power and output power of the generator,Synchronous generatorThe relationship between the frequency of generated electric energy and its speed is f=np/60. When the pole pair P of the generator is constant, the frequency f is determined by the speed n.When the load of the generator increases, the mechanical torque input by the generator is less than the electromagnetic torque output, and the speed of the motor decreases, which causes the decrease of the power frequency, otherwise the frequency will rise.The voltage fluctuation is mainly caused by the change of load size and load nature (the change of active power and reactive power).The basic task of hydropower unit control is to continuously adjust the active and reactive power output of the hydropower unit according to the load changes, and maintain the unit speed (frequency) and output terminal voltage within the specified range.The frequency of hydraulic generator set is controlled byTurbine governorThe stability of terminal voltage can be realized by the generatorExcitation regulatorTo complete.The regulation of the two is relatively independent, with little interaction.[2]
