With the increasing importance of environmental pollution and waste of resources, the importance of new energy has become more and more obvious. As a representative energy source in the new energy family, solar energy has become widely used. This paper introduces the current status and characteristics of solar thermal power generation, and shows that solar thermal power generation has a good application prospect.
1 Solar power system
1.1 Introduction to Solar Energy
Solar energy is the energy generated by the continuous nuclear fusion reaction process inside the sun. It is the most important basic energy source of various renewable energy sources and the most abundant energy source available to humans. The sun's annual radiant energy projected onto the ground is as high as 1.05 & TImes; 1018 kWh, equivalent to 1.3 & TImes; 10.6 billion tons of standard coal, about 10,000 times the annual energy consumption of the world. According to the current solar mass consumption rate, it can maintain 6 & TImes; 1010 years, it can be said that it is "inexhaustible, inexhaustible" energy.
Earth's wind energy, water energy, ocean temperature difference energy, wave energy and biomass energy, and some tidal energy are all from the sun; even fossil fuels on the earth (such as coal, oil, natural gas, etc.) are fundamentally ancient. The stored solar energy, so the broad range of solar energy is very large, and the narrow solar energy is limited to the direct conversion of solar radiant energy, photo-electricity and photochemistry. Solar energy is both primary energy and renewable energy. It is rich in resources and can be used free of charge without transportation and without any pollution to the environment.
1.2 Solar thermal power generation
Modern solar technology can condense sunlight and use its energy to produce hot water, steam and electricity. Solar Thermal. The principle is to focus the sunlight reflected by the mirror on a glass tube called a receiver, and the hollow glass tube allows oil to flow through. The sunlight reflected from the mirror will heat up the oil in the tube, generate steam, and then the steam will drive the turbine to generate electricity.
In addition to using appropriate technology to collect solar energy, buildings can also use the sun's light and heat by adding suitable equipment to the design, such as giant south-facing windows or building materials that absorb and slowly release solar heat. . At the right place, the long-term cost of solar energy is close to or even lower than that of traditional fossil fuels.
2 Solar thermal power generation control technology
2.1 Current status and characteristics of solar thermal power generation control system
For the solar thermal power generation control system, the characteristics of the power generation control system are similar or equivalent to the control system of the conventional thermal power generating unit. The following describes the development status and characteristics of the solar thermal power generation island control system for the conventional thermal power unit distributed control system. ?
Based on the system structure and control model, a reasonable control system is designed, and the parameter setting method is given. When the unit is running stably and the load is changed according to the grid load requirements, the unit parameters are operated within a reasonable range, and no over-temperature and over-pressure occur. Tripping and other faults are one of the main objectives of the thermal power unit automation control system. The thermal power system of the thermal power generating unit is complicated, and more thermal protection projects are set up. Under abnormal conditions, the unit is safely shut down to avoid major equipment damage due to operational errors. In addition, in order to achieve orderly start and stop of the unit and equipment, several sequential control loops are also provided. Typical thermal power unit control systems include: engine SOE, boiler protection, pre-furnace oil system, sealed air, fire detection cooling system, micro-oil ignition system, milling system and fire detection, fuel and fire detection system, coordination System, water supply main control system, combustion main control, delivery, air intake, primary air system, superheated steam temperature, reheat steam temperature system, wind smoke system, boiler start system, soot blowing system, desulfurization system, denitration system, steam turbine Body system, bypass system, regenerative heating system, generator cooling system, lubrication system, generator set, excitation system, plant power system, small steam turbine system, auxiliary workshop system, etc. ?
The thermal power unit automation device is mainly a distributed control system DCS programming logic controller? PLC. DCS is generally used for host control, and PLC is generally used for auxiliary workshop control, such as coal handling control and chemical water treatment control. Although there are many types of distributed control systems, the most basic distributed control systems generally have the structure shown in the figure. The controller (or field control station, process control station, distributed processing unit, etc.) belongs to the decentralized control part and is connected to the field instrument; the engineering station, the operator station and the server belong to the operation management part. The decentralized control part and the operation management part are connected as a whole through a computer network. The distributed control system is connected to other systems through an open network interface.
2.2 Solar thermal power generation system power station operation mode
2.2.1 Normal morning start?
The heliostats in each area are in their natural orientation, and they are not in the standby state as shown in Figure 4 (Standby, that is, the focused rays of the heliostats in each area are respectively positioned in the air), at this time the whole plant starts running. It is called “normal morning startâ€, and the basic logic judgment order of each module during startup. ?
2.2.2 Cold start
During the start-up operation of the whole plant, the heat absorber is affected by the heat loss, and the state parameters at startup are corresponding to the surrounding environment. After the previous operation of the heliostat field, it is in the standby state as shown in Figure 5. For the whole plant "cold start". The logical sequence in which each module operates is the same as the normal morning start, except that the mirror field is activated from the standby state rather than the natural orientation state. ?
2.2.3 Hot start?
When the heat sink and the steam turbine are decoupled for some reasons such as irradiation, high wind, etc., some heat absorbers with isolation doors can keep steam with a certain pressure and temperature inside, when irradiation, wind speed, etc. Changes in external conditions make the heat sink meet the start-up operation called “hot startâ€, which will reach the rated operating condition in a short time, depending on the design of the heat sink. This type of startup is basically the same except that the mirror field is in the standby state instead of the natural orientation state, and the steam parameters can reach the rated value faster and reduce the bypass flow.
2.2.4 Normal operation?
When the startup is completed, the whole plant is in normal operation under the condition that the external conditions have no drastic changes, and the power generation of the whole plant is directly related to the irradiation change.
2.2.5 Cloud cover operation?
When the intensity of the radiation projected onto the surface of the heat sink is lower than the lower limit of the design of the heat sink to N (determined by the specific design) time step, the heliostat field begins to initiate the program of deflection to the standby state; When the turbine inlet pressure is lower than the set value (to ensure continuous connection with the grid, the set value is as small as possible), and under the condition of sufficient storage, steam is automatically generated by the energy storage system. If the irradiance is restored before the heliostat field is fully deflected, the heliostat is again projected from the current position to the surface of the heat sink. The basic logical judgment of the process. ?
2.2.6 Closed at night?
When the intensity of the concentrating radiation projected onto the surface of the heat absorber in the evening is lower than the lower limit of the design, the program for automatically starting the mirror field from the position of the focus heat absorber to the standby state is controlled, and the voltage regulating and temperature regulating device is controlled to reduce The load on the turbine is finally cracked by the generator set and the grid. ?
2.2.7 Accident emergency operation?
The accident mainly comes from two aspects of the heat absorber and the mirror field: the fault of the heat sink mainly occurs in the water supply system, such as the failure of the feed water pump and the mechanical or electrical failure of the pipeline. At this time, the surface of the heat absorber is still very strong. Light distribution, so the water spray desuperheating system must be activated and the safety valve of the heat sink must be activated while the heliostat field deflection is activated. The failure of the mirror field usually comes from a communication or power interruption, in which case the backup Power Supply must be enabled to bias the heliostat to the standby position.
3 Conclusion
This paper gives a detailed introduction to the status quo and characteristics of solar thermal power generation control technology, and explains the operation mode of solar thermal power generation system. In view of today's serious environmental pollution, solar energy, as the most favored green energy source in new energy, can not only alleviate the problem of environmental pollution, but also bring great business opportunities.
APM offers 3 Phase AC Power Source system. It`s single 3-phase output Programmable AC Power Supply which provides with high power density. With high speed DSP+CPLD control, high frequency PWM technology, active PFC design, It is able to provide not only stable DC/AC Output Power ,but also 3-phase / 1-phase output.
The 3 Phase Ac Power Supply is featured with high power density, high reliability and high precision, meanwhile it possesses operation interface of touch screen and keys manually. It is able to analog output normal or abnormal power input for electrical device to meet test requirements, which is applicable to electric, lighting, aviation sectors, etc. It could be applied to enterprise`s production test as well.
Some features as below:
- 5.6" large touch color screen, possess complete functions and easy to operate.
- Support for USB data import/export and screen snap from front panel.
- AC+DC mixed or independent output mode for voltage DC offset simulation.
- Capable of setting voltage and current output restriction, support for constant current output mode.
- Capable of setting output slope of voltage and frequency.
- Capable of setting ON/OFF phase angle.
- With reverse current protection to avoid current flowing backward.
- Built-in power meter, which is capable of measuring 5 electrical parameters per phase, including voltage, current, power, etc.
- Support mA current measurement function.
Three Phase AC Source System,Programmable 3 Phase Ac Power Supply,Ac Source System,Three Phase Source
APM Technologies (Dongguan) Co., Ltd , https://www.apmpowersupply.com