Although the search for new energy has a considerable history, the world's environmental pollution and energy shortages have forced people to work harder to find and develop new energy sources. In the process of finding and developing new energy sources, people naturally turn their attention to various renewable alternative energy sources. Photovoltaic Power Generation is one of them. Although the practical application of photovoltaic power generation has various limitations, with the decrease of the cost of photovoltaic power generation and the increase of the cost of fossil power generation and the reduction of fossil energy, the cost of photovoltaic power generation will one day be equivalent to the cost of traditional power generation. By then, photovoltaic power generation will gradually enter the commercialization stage. After the grid-connected photovoltaic power generation form scale, what kind of influence will be formed on the grid is the problem that this article wants to discuss.
First, the basic principles of photovoltaic power generation 1. The composition of solar photovoltaic power generation system Solar photovoltaic power generation system consists of solar photovoltaic battery, photovoltaic system battery controller, battery and AC-DC inverter is the main component. The core components are photovoltaic cells and controllers. The role of various components in the system is:
Photovoltaic cells: photoelectric conversion.
Controller: Process control that acts on the entire system. There are many types of controllers used in photovoltaic power generation systems, such as 2-point controllers, multi-channel sequential controllers, intelligent controllers, and high-power tracking charge controllers. Currently, most of the controllers used in China are simply designed controllers. The controller is only used for communication systems and larger photovoltaic power plants.
Battery: A battery is a key component of a photovoltaic power generation system and is used to store electricity converted from photovoltaic cells. At present, China does not have a dedicated battery for photovoltaic systems, but uses a conventional lead-acid battery.
AC-DC inverter: Since its function is AC-DC conversion, the most important indicator of this component is reliability and conversion efficiency. Grid-connected inverters use maximum power tracking technology to maximize the conversion of photovoltaic cell power into the grid.
2. Solar photovoltaic panels:
Solar cells are mainly made of single crystal silicon. Monocrystalline silicon is used to make a pn junction in a diode. The working principle is similar to that of a diode. However, in the diode, the external electric field that pushes the hole and electron movement of the PN junction is the solar field and the radiant heat (*) in the solar cell that pushes and influences the movement of the PN junction hole and the electron. It is also known as the principle of photovoltaic effect. At present, the efficiency of photoelectric conversion, that is, the efficiency of photovoltaic cells is about 13%-15% for monocrystalline silicon and 11%-13% for polysilicon. The latest technology also includes photovoltaic thin-film batteries.
3. Classification of solar photovoltaic power generation system:
At present, solar photovoltaic power generation systems can be roughly divided into three categories: off-grid photovoltaic storage systems, photovoltaic grid-connected power generation systems and the former two hybrid systems.
A) Off-grid photovoltaic storage system. This is a common solar application. It has been applied at home and abroad for several years. The system is relatively simple and adaptable. The scope of use is limited only because of the large size of its battery and the difficulty of maintenance.
B) Photovoltaic grid-connected power generation systems, when the power load is large, the solar power is insufficient to purchase power from the mains. When the load is small, or when there is no power available, excess power can be sold to the utility power. Under the premise of backing grid, the system saved the battery, which expanded the scope and flexibility of use, and reduced the cost.
C) A, B both hybrid system, which is a system between the above two parties. The program has strong adaptability. For example, it can adjust its own power generation strategy based on the peak-to-valley power price of the power grid. However, its cost and operating costs are higher than the above two options.
Second, the advantages of photovoltaic power Into the 70's, due to the impact of the two oil crises, photovoltaic power generation in the world has been highly valued and developed very rapidly. From a long-term perspective, photovoltaic power generation will enter the electricity market with decentralized power sources and will partially replace conventional energy sources. Regardless of the recent and near-term perspective, photovoltaic power generation can be used as a supplement to conventional energy sources. It can be used in solving specific application fields such as communications and signal power supply, and civil residential electricity demand in remote and uncharged areas. It has both environmental protection and energy strategy. Great significance. The advantages of photovoltaic power generation are fully reflected in the following aspects:
1. Fully clean. (If using a battery scheme, consider the disposal of used batteries)
2. Absolute security. (The grid-connected voltage is generally less than 220V)
3. Relatively extensive.
4. Really long life and maintenance-free.
5. Preliminary practicality.
6. Adequacy of resources and potential economics.
Third, photovoltaic power generation limitations.
Everything always has two sides. There are too many articles presenting the advantages and advantages of photovoltaic power generation. It is necessary to point out some limitations of photovoltaic power generation. Solar energy has the disadvantages of low energy density and poor stability, and is affected by geographical distribution, seasonal changes, and alternation of day and night. The limitations of photovoltaic power generation include the following aspects:
1. Time period limitation. Since photovoltaic power generation conditions are solar, photovoltaic power generation equipment can work normally to generate electricity. Therefore, during the day and night, the load of photovoltaic power generation in all seasons of spring, summer, autumn and winter is greatly affected. In order to cope with this situation, the power grid has to be equipped with a corresponding capacity of the generator in rotating standby.
2. Geographical limitations. Photovoltaic power generation equipment can basically only be attached to the building installation and construction, that is, the so-called photovoltaic roof power supply in situ. If you leave the building to build photovoltaic power, it will greatly increase costs or damage the environment and ecology.
3. Meteorological conditions are limited. Climate impact on photovoltaic power generation. When photovoltaic-based grid-connected power generation is used without a battery solution, if the climate over a city changes greatly, it will cause a large fluctuation in the power load; when the air quality over a city is such as air pollution, or the visibility deteriorates, such as fog, cloudy, etc. Will make photovoltaic power generation decline online or in real time.
4. Capacity transmission limitations. After solving the problem of the cost of photovoltaic power generation, high-power, high-voltage, long-distance transmission of power from the desert area to the load center, since photovoltaic power generation does not have the rotational inertia of conventional motors, governors and excitation systems, will bring to the AC grid. New economic and stability issues. Irrespective of the use of AC or DC high-voltage high-power remote transmission of electricity from desert areas, the limitations of 1, 2 and 3 above will greatly increase the transmission cost per kilowatt. This issue will be discussed below.
5. Light energy conversion efficiency is low. Compared with the conversion efficiency of traditional energy (mineral energy, petroleum, water energy, atomic energy, etc.), the conversion efficiency of photovoltaic energy is not satisfactory.
IV. Future Prospects of Photovoltaic Power The photovoltaic industry in China is growing at an annual rate of 30. The average annual growth rate of global solar cell output in the last three years was as high as 49.8. According to the calculations of Japan's new energy plan, the EU's renewable energy white paper, and the US Photovoltaic Program, the installed capacity of grid-connected photovoltaic power generation in the world will reach 15GW (15 million kilowatts by 2010, which will still be less than the total installed capacity of the world's electricity generation), to 2030. The installed capacity of photovoltaic power generation in the world will reach 300GW (the output value of the entire industry may exceed US$300 billion by that time). By 2040, photovoltaic power generation will reach 15-20 of the total global power generation. According to this plan, from 2010 to 2040, the compound growth rate of the PV industry will be as high as 25 (see information: 15). Among them, there will be greater development in grid-connected applications, resulting in three major application areas (eg, 46), off-grid power supply (approximately 27), and communications station (approximately 21) (see information: 16).
The energy of the sun is almost limitless to humans, but in reality, the resources available to obtain solar energy resources on Earth are limited. Not as great as some articles say. For example, when we install solar water heaters on the roof, we lose the opportunity to install solar cells. With the exception of buildings and deserts, building solar panels at Other locations will be unrealistic and costly. This is not just because of the huge cost. The problem is obvious. The main problem is that leaving buildings and deserts to build photovoltaic power stations will damage the environment and ecology. You will find that you will not be able to grow grass under the solar panels. In short, energy saving is an eternal topic for humanity. In a sense, when old technologies and products are eliminated, the energy that originally produced these technologies and products was wasted. Those who go abroad for investigation often find that Western developed countries still use products and equipment in the 20-30s in some cases. They are not trying to protect “historic sitesâ€. In a sense, they are saving energy. The replacement of new and old products and technologies is at the expense of energy. The replacement of too fast products will accelerate the consumption of energy. Of course, there is a need for an overall economic indicator to determine energy consumption. Should we consider the issue of "used energy" conservation? (**)
On the other hand, any advanced technology that is necessary for commercial use is that prices are acceptable to the market. If the cost of use is too high, no matter how good the technology will be, it will only stay in the laboratory or demonstration project stage.
V. Impact of Photovoltaic Power Grid Integration on Future Power Grids With the promulgation and implementation of the “Renewable Energy Law†in China, the rising conventional energy prices and the oil price approaching $100, the use of solar energy technology has been rapidly developed around the world. Among them, photovoltaic grid-connected power generation technology has developed very rapidly. At present, the main factor that restricts photovoltaic power generation is cost. The cost of solar photovoltaic power generation is high (more than 30,000 yuan per kilowatt), and the cost of power generation is high (1.5 yuan/kWh or more). With the reduction of the cost of photovoltaic power generation and the increase of the cost of energy-consuming power generation, the cost of photovoltaic power generation will one day be equivalent to the cost of conventional power generation. By then, photovoltaic power generation will enter the stage of commercialization. To welcome this day ahead, we will need to consider in advance the impact of grid-connected photovoltaic power generation on the technical, economic, policy, and environmental benefits of existing power generation models. Let us suppose that this era has come and that there is no major change in the existing power generation mode. What problems will the PV grid generate for us while generating benefits for the existing grid?
Since solar photovoltaic power generation belongs to energy sources with low energy density, poor stability, and poor regulation capability, the amount of power generation is greatly affected by weather and regions. After grid-connected power generation, it will affect the safety, stability, economic operation, and power supply quality of the power grid. . It is not clear as to what effect it has. We know that current electric energy cannot be stored on a large scale at low cost, and it cannot be stored on a large scale at low cost in the foreseeable future. This makes the application of photovoltaic power generation constrained by physical factors, but also by geographical constraints. However, with the development of technology and the market, photovoltaic grid-connected power generation will be effective when the on-grid electricity generated by photovoltaic power generation is in a comparable order of magnitude and becomes a non-negligible part of power generation in power grids and power plants such as thermal power plants, hydropower, and nuclear power. There are the following problems caused by the power generation model and the technical, economic, policy, and environmental benefits of the grid: (If the photovoltaic grid-connected power generation system uses a battery solution, the advantages and advantages of photovoltaic grid-connected power generation will be greatly reduced. However, it is optimized for photovoltaic grid-connected power generation. The configured battery system can partially solve the problems presented in 1, 2 and 3 below.)
1. The impact of load peaks and valleys on the power grid. Because photovoltaic grid-connected power generation systems do not have peak-shaving and frequency-regulating capabilities, this will impact the grid's early and late peak loads. The increased generating capacity of photovoltaic grid-connected power generation systems does not reduce the number of conventional rotary turbines. The grid must prepare a large number of rotating standby units for photovoltaic power generation systems to solve the peak-peaking problems of early and late peaks. Photovoltaic grid-connected power generation systems supply power to the grid at the expense of a reduction in the number of hours of utilization of the unit. This, of course, is something that power generation companies do not want to see.
2. Changes in day and night, the time difference between the eastern and western regions, and the impact of the season on the power grid. Due to the periodic nature of sunlight and load, the increase in photovoltaic grid-connected power generation does not reduce the demand for installed power grid capacity.
3. Changes in weather conditions. When a city's photovoltaic rooftop grid-connected power reaches a certain scale, if the geographical weather changes drastically, the grid will provide enough regional rotating standby units and reactive compensation capacity for photovoltaic grid-connected power generation systems to control and adjust the frequency of the system. And voltage. In this case, the grid will guarantee the safe and stable operation of the grid at the expense of economic operation.
4. Long-distance photovoltaic power transmission. When photovoltaic grid-connected power generation is economically and technically feasible for transmission of electricity over long distances, photovoltaic grid-connected power generation has no rotational inertia, governors and excitation systems, and it will bring new stability problems to the AC grid. If photovoltaic grid-connected power generation scales adopt high-voltage AC/DC power transmission, it will bring stability and economic problems to the AC system adjacent to the photovoltaic DC power transmission system. (Specially used for photovoltaic grid-connected power transmission lines, due to the use of efficiency Low, it will restrict the use of desert solar energy. Transmission lines used to transport electricity through the grid or the photovoltaic grid-connected power generation system are not economical due to the low loading rate.) Whether high-voltage AC or DC transmission is used, photovoltaic grid-connected Power stations must be equipped with automatic reactive pressure regulators. As for the impact on the stability of the power grid, the mathematical model (including the power supply model and load model) of photovoltaic power generation in the stability calculation of the power grid has not yet been seen. It is unclear how much impact photovoltaic grid-connected generation will have on the safe and stable operation of the grid.
5. The problem of reducing consumption; One of the major advantages of photovoltaic grid-connected generation is the consumption of alternative fossil fuels. Since PV grid-connected power generation increases the rotational or thermal reserve of rotating generators in power plants, the actual reduction rate of photovoltaic grid-connected power generation should be deducted from the energy lost in rotating standby or hot standby. The efficiency reduction of photovoltaic grid-connected power generation should take into account the loss of efficiency due to the reduction in the number of hours of utilization of power generation company units due to the power provided by photovoltaic grid-connected power generation systems. Since the power system operates as a whole, the photovoltaic grid-connected power transmission to the grid will infringe on the interests of other power generators. This is a question that policy makers need to consider. This is due to the fact that not only hydropower plants are rotating backups when the grid is considered safe, stable, and economical. Therefore, the theoretical total reduction of grid-connected PV generation in the system should be multiplied by a factor of less than the theoretical reduction of the standard coal consumption, and the proportion of the plant power consumption of the spinning reserve unit should be reduced.
Here is a formula to determine the actual power reduction effect of photovoltaic power generation:
W=[(Wc/Wn)*Wp-(Pc/Pn)Pd);1
1) W--The actual consumption reduction of photovoltaic grid-connected power generation (standard coal);
2) Wc--the total generation of thermal power in the grid;
3) Wn--the total power generation of the grid;
4) Wp--Theoretical consumption reduction of photovoltaic grid-connected generation (standard coal)
5) The total plant power consumption of Pc--thermal power units (standard coal);
6) Pn--The total plant power consumption in the power grid (standard coal);
7)Pd--Skid power loss (standard coal) of the rotating standby unit.
6.Environmental protection issues; whether the emission reduction effect brought by photovoltaic power generation should only consider the sulfur dioxide and carbon dioxide emitted by thermal power remains to be studied, because when photovoltaic grid-connected power generation, the same power grid is often reduced when considering the safety, stability and economic operation of the power grid. It is not only the thermal power plants that are making efforts, but when considering rotating backups, it is not just the hydropower plants that are responsible for the rotation reserve task (the loss of the hydropower plant that undertakes the rotary backup task is small). Therefore, when considering the reduction contribution of photovoltaic grid-connected power generation system, it should also be multiplied by a factor less than one before the theoretical value. This conclusion is not as optimistic as some articles say.
7. Incidentally, wind power generation also has environmental and ecological problems. Foreign environmentalists have pointed out that large-scale wind power stations are often built on monsoon winds, which is often the best route for migratory birds.
VI. Conclusion The advantages of photovoltaic power generation are to solve the energy power of communications in off-grid areas, microwaves, etc., to disperse the small-capacity power consumption in the population areas, and to provide electricity locally for buildings that have conditionally established photovoltaic roofs. In the future development planning of the power grid, the impact of off-grid photovoltaic power generation and photovoltaic grid-connected power generation on the power grid and mathematical models should be fully considered for load forecasting. The off-grid PV system can be considered as an online active variable load model (herein referred to as the off-grid PV system in the city, but also the load supplied by the municipal grid). If photovoltaic grid-connected power generation systems are supplied with 110V or 220V grid-connected power, photovoltaic grid-connected power generation systems can also be considered as active load models that can change from negative to positive. Through the above analysis, the long-term positioning of photovoltaic grid-connected power can only serve as an important supplementary means for energy conservation and consumption reduction of the power grid. If it exceeds this strategic positioning, it will result in investment and additional energy waste, and the optimistic view on reducing pollution emissions will also be greatly reduced.
First, the basic principles of photovoltaic power generation 1. The composition of solar photovoltaic power generation system Solar photovoltaic power generation system consists of solar photovoltaic battery, photovoltaic system battery controller, battery and AC-DC inverter is the main component. The core components are photovoltaic cells and controllers. The role of various components in the system is:
Photovoltaic cells: photoelectric conversion.
Controller: Process control that acts on the entire system. There are many types of controllers used in photovoltaic power generation systems, such as 2-point controllers, multi-channel sequential controllers, intelligent controllers, and high-power tracking charge controllers. Currently, most of the controllers used in China are simply designed controllers. The controller is only used for communication systems and larger photovoltaic power plants.
Battery: A battery is a key component of a photovoltaic power generation system and is used to store electricity converted from photovoltaic cells. At present, China does not have a dedicated battery for photovoltaic systems, but uses a conventional lead-acid battery.
AC-DC inverter: Since its function is AC-DC conversion, the most important indicator of this component is reliability and conversion efficiency. Grid-connected inverters use maximum power tracking technology to maximize the conversion of photovoltaic cell power into the grid.
2. Solar photovoltaic panels:
Solar cells are mainly made of single crystal silicon. Monocrystalline silicon is used to make a pn junction in a diode. The working principle is similar to that of a diode. However, in the diode, the external electric field that pushes the hole and electron movement of the PN junction is the solar field and the radiant heat (*) in the solar cell that pushes and influences the movement of the PN junction hole and the electron. It is also known as the principle of photovoltaic effect. At present, the efficiency of photoelectric conversion, that is, the efficiency of photovoltaic cells is about 13%-15% for monocrystalline silicon and 11%-13% for polysilicon. The latest technology also includes photovoltaic thin-film batteries.
3. Classification of solar photovoltaic power generation system:
At present, solar photovoltaic power generation systems can be roughly divided into three categories: off-grid photovoltaic storage systems, photovoltaic grid-connected power generation systems and the former two hybrid systems.
A) Off-grid photovoltaic storage system. This is a common solar application. It has been applied at home and abroad for several years. The system is relatively simple and adaptable. The scope of use is limited only because of the large size of its battery and the difficulty of maintenance.
B) Photovoltaic grid-connected power generation systems, when the power load is large, the solar power is insufficient to purchase power from the mains. When the load is small, or when there is no power available, excess power can be sold to the utility power. Under the premise of backing grid, the system saved the battery, which expanded the scope and flexibility of use, and reduced the cost.
C) A, B both hybrid system, which is a system between the above two parties. The program has strong adaptability. For example, it can adjust its own power generation strategy based on the peak-to-valley power price of the power grid. However, its cost and operating costs are higher than the above two options.
Second, the advantages of photovoltaic power Into the 70's, due to the impact of the two oil crises, photovoltaic power generation in the world has been highly valued and developed very rapidly. From a long-term perspective, photovoltaic power generation will enter the electricity market with decentralized power sources and will partially replace conventional energy sources. Regardless of the recent and near-term perspective, photovoltaic power generation can be used as a supplement to conventional energy sources. It can be used in solving specific application fields such as communications and signal power supply, and civil residential electricity demand in remote and uncharged areas. It has both environmental protection and energy strategy. Great significance. The advantages of photovoltaic power generation are fully reflected in the following aspects:
1. Fully clean. (If using a battery scheme, consider the disposal of used batteries)
2. Absolute security. (The grid-connected voltage is generally less than 220V)
3. Relatively extensive.
4. Really long life and maintenance-free.
5. Preliminary practicality.
6. Adequacy of resources and potential economics.
Third, photovoltaic power generation limitations.
Everything always has two sides. There are too many articles presenting the advantages and advantages of photovoltaic power generation. It is necessary to point out some limitations of photovoltaic power generation. Solar energy has the disadvantages of low energy density and poor stability, and is affected by geographical distribution, seasonal changes, and alternation of day and night. The limitations of photovoltaic power generation include the following aspects:
1. Time period limitation. Since photovoltaic power generation conditions are solar, photovoltaic power generation equipment can work normally to generate electricity. Therefore, during the day and night, the load of photovoltaic power generation in all seasons of spring, summer, autumn and winter is greatly affected. In order to cope with this situation, the power grid has to be equipped with a corresponding capacity of the generator in rotating standby.
2. Geographical limitations. Photovoltaic power generation equipment can basically only be attached to the building installation and construction, that is, the so-called photovoltaic roof power supply in situ. If you leave the building to build photovoltaic power, it will greatly increase costs or damage the environment and ecology.
3. Meteorological conditions are limited. Climate impact on photovoltaic power generation. When photovoltaic-based grid-connected power generation is used without a battery solution, if the climate over a city changes greatly, it will cause a large fluctuation in the power load; when the air quality over a city is such as air pollution, or the visibility deteriorates, such as fog, cloudy, etc. Will make photovoltaic power generation decline online or in real time.
4. Capacity transmission limitations. After solving the problem of the cost of photovoltaic power generation, high-power, high-voltage, long-distance transmission of power from the desert area to the load center, since photovoltaic power generation does not have the rotational inertia of conventional motors, governors and excitation systems, will bring to the AC grid. New economic and stability issues. Irrespective of the use of AC or DC high-voltage high-power remote transmission of electricity from desert areas, the limitations of 1, 2 and 3 above will greatly increase the transmission cost per kilowatt. This issue will be discussed below.
5. Light energy conversion efficiency is low. Compared with the conversion efficiency of traditional energy (mineral energy, petroleum, water energy, atomic energy, etc.), the conversion efficiency of photovoltaic energy is not satisfactory.
IV. Future Prospects of Photovoltaic Power The photovoltaic industry in China is growing at an annual rate of 30. The average annual growth rate of global solar cell output in the last three years was as high as 49.8. According to the calculations of Japan's new energy plan, the EU's renewable energy white paper, and the US Photovoltaic Program, the installed capacity of grid-connected photovoltaic power generation in the world will reach 15GW (15 million kilowatts by 2010, which will still be less than the total installed capacity of the world's electricity generation), to 2030. The installed capacity of photovoltaic power generation in the world will reach 300GW (the output value of the entire industry may exceed US$300 billion by that time). By 2040, photovoltaic power generation will reach 15-20 of the total global power generation. According to this plan, from 2010 to 2040, the compound growth rate of the PV industry will be as high as 25 (see information: 15). Among them, there will be greater development in grid-connected applications, resulting in three major application areas (eg, 46), off-grid power supply (approximately 27), and communications station (approximately 21) (see information: 16).
The energy of the sun is almost limitless to humans, but in reality, the resources available to obtain solar energy resources on Earth are limited. Not as great as some articles say. For example, when we install solar water heaters on the roof, we lose the opportunity to install solar cells. With the exception of buildings and deserts, building solar panels at Other locations will be unrealistic and costly. This is not just because of the huge cost. The problem is obvious. The main problem is that leaving buildings and deserts to build photovoltaic power stations will damage the environment and ecology. You will find that you will not be able to grow grass under the solar panels. In short, energy saving is an eternal topic for humanity. In a sense, when old technologies and products are eliminated, the energy that originally produced these technologies and products was wasted. Those who go abroad for investigation often find that Western developed countries still use products and equipment in the 20-30s in some cases. They are not trying to protect “historic sitesâ€. In a sense, they are saving energy. The replacement of new and old products and technologies is at the expense of energy. The replacement of too fast products will accelerate the consumption of energy. Of course, there is a need for an overall economic indicator to determine energy consumption. Should we consider the issue of "used energy" conservation? (**)
On the other hand, any advanced technology that is necessary for commercial use is that prices are acceptable to the market. If the cost of use is too high, no matter how good the technology will be, it will only stay in the laboratory or demonstration project stage.
V. Impact of Photovoltaic Power Grid Integration on Future Power Grids With the promulgation and implementation of the “Renewable Energy Law†in China, the rising conventional energy prices and the oil price approaching $100, the use of solar energy technology has been rapidly developed around the world. Among them, photovoltaic grid-connected power generation technology has developed very rapidly. At present, the main factor that restricts photovoltaic power generation is cost. The cost of solar photovoltaic power generation is high (more than 30,000 yuan per kilowatt), and the cost of power generation is high (1.5 yuan/kWh or more). With the reduction of the cost of photovoltaic power generation and the increase of the cost of energy-consuming power generation, the cost of photovoltaic power generation will one day be equivalent to the cost of conventional power generation. By then, photovoltaic power generation will enter the stage of commercialization. To welcome this day ahead, we will need to consider in advance the impact of grid-connected photovoltaic power generation on the technical, economic, policy, and environmental benefits of existing power generation models. Let us suppose that this era has come and that there is no major change in the existing power generation mode. What problems will the PV grid generate for us while generating benefits for the existing grid?
Since solar photovoltaic power generation belongs to energy sources with low energy density, poor stability, and poor regulation capability, the amount of power generation is greatly affected by weather and regions. After grid-connected power generation, it will affect the safety, stability, economic operation, and power supply quality of the power grid. . It is not clear as to what effect it has. We know that current electric energy cannot be stored on a large scale at low cost, and it cannot be stored on a large scale at low cost in the foreseeable future. This makes the application of photovoltaic power generation constrained by physical factors, but also by geographical constraints. However, with the development of technology and the market, photovoltaic grid-connected power generation will be effective when the on-grid electricity generated by photovoltaic power generation is in a comparable order of magnitude and becomes a non-negligible part of power generation in power grids and power plants such as thermal power plants, hydropower, and nuclear power. There are the following problems caused by the power generation model and the technical, economic, policy, and environmental benefits of the grid: (If the photovoltaic grid-connected power generation system uses a battery solution, the advantages and advantages of photovoltaic grid-connected power generation will be greatly reduced. However, it is optimized for photovoltaic grid-connected power generation. The configured battery system can partially solve the problems presented in 1, 2 and 3 below.)
1. The impact of load peaks and valleys on the power grid. Because photovoltaic grid-connected power generation systems do not have peak-shaving and frequency-regulating capabilities, this will impact the grid's early and late peak loads. The increased generating capacity of photovoltaic grid-connected power generation systems does not reduce the number of conventional rotary turbines. The grid must prepare a large number of rotating standby units for photovoltaic power generation systems to solve the peak-peaking problems of early and late peaks. Photovoltaic grid-connected power generation systems supply power to the grid at the expense of a reduction in the number of hours of utilization of the unit. This, of course, is something that power generation companies do not want to see.
2. Changes in day and night, the time difference between the eastern and western regions, and the impact of the season on the power grid. Due to the periodic nature of sunlight and load, the increase in photovoltaic grid-connected power generation does not reduce the demand for installed power grid capacity.
3. Changes in weather conditions. When a city's photovoltaic rooftop grid-connected power reaches a certain scale, if the geographical weather changes drastically, the grid will provide enough regional rotating standby units and reactive compensation capacity for photovoltaic grid-connected power generation systems to control and adjust the frequency of the system. And voltage. In this case, the grid will guarantee the safe and stable operation of the grid at the expense of economic operation.
4. Long-distance photovoltaic power transmission. When photovoltaic grid-connected power generation is economically and technically feasible for transmission of electricity over long distances, photovoltaic grid-connected power generation has no rotational inertia, governors and excitation systems, and it will bring new stability problems to the AC grid. If photovoltaic grid-connected power generation scales adopt high-voltage AC/DC power transmission, it will bring stability and economic problems to the AC system adjacent to the photovoltaic DC power transmission system. (Specially used for photovoltaic grid-connected power transmission lines, due to the use of efficiency Low, it will restrict the use of desert solar energy. Transmission lines used to transport electricity through the grid or the photovoltaic grid-connected power generation system are not economical due to the low loading rate.) Whether high-voltage AC or DC transmission is used, photovoltaic grid-connected Power stations must be equipped with automatic reactive pressure regulators. As for the impact on the stability of the power grid, the mathematical model (including the power supply model and load model) of photovoltaic power generation in the stability calculation of the power grid has not yet been seen. It is unclear how much impact photovoltaic grid-connected generation will have on the safe and stable operation of the grid.
5. The problem of reducing consumption; One of the major advantages of photovoltaic grid-connected generation is the consumption of alternative fossil fuels. Since PV grid-connected power generation increases the rotational or thermal reserve of rotating generators in power plants, the actual reduction rate of photovoltaic grid-connected power generation should be deducted from the energy lost in rotating standby or hot standby. The efficiency reduction of photovoltaic grid-connected power generation should take into account the loss of efficiency due to the reduction in the number of hours of utilization of power generation company units due to the power provided by photovoltaic grid-connected power generation systems. Since the power system operates as a whole, the photovoltaic grid-connected power transmission to the grid will infringe on the interests of other power generators. This is a question that policy makers need to consider. This is due to the fact that not only hydropower plants are rotating backups when the grid is considered safe, stable, and economical. Therefore, the theoretical total reduction of grid-connected PV generation in the system should be multiplied by a factor of less than the theoretical reduction of the standard coal consumption, and the proportion of the plant power consumption of the spinning reserve unit should be reduced.
Here is a formula to determine the actual power reduction effect of photovoltaic power generation:
W=[(Wc/Wn)*Wp-(Pc/Pn)Pd);1
1) W--The actual consumption reduction of photovoltaic grid-connected power generation (standard coal);
2) Wc--the total generation of thermal power in the grid;
3) Wn--the total power generation of the grid;
4) Wp--Theoretical consumption reduction of photovoltaic grid-connected generation (standard coal)
5) The total plant power consumption of Pc--thermal power units (standard coal);
6) Pn--The total plant power consumption in the power grid (standard coal);
7)Pd--Skid power loss (standard coal) of the rotating standby unit.
6.Environmental protection issues; whether the emission reduction effect brought by photovoltaic power generation should only consider the sulfur dioxide and carbon dioxide emitted by thermal power remains to be studied, because when photovoltaic grid-connected power generation, the same power grid is often reduced when considering the safety, stability and economic operation of the power grid. It is not only the thermal power plants that are making efforts, but when considering rotating backups, it is not just the hydropower plants that are responsible for the rotation reserve task (the loss of the hydropower plant that undertakes the rotary backup task is small). Therefore, when considering the reduction contribution of photovoltaic grid-connected power generation system, it should also be multiplied by a factor less than one before the theoretical value. This conclusion is not as optimistic as some articles say.
7. Incidentally, wind power generation also has environmental and ecological problems. Foreign environmentalists have pointed out that large-scale wind power stations are often built on monsoon winds, which is often the best route for migratory birds.
VI. Conclusion The advantages of photovoltaic power generation are to solve the energy power of communications in off-grid areas, microwaves, etc., to disperse the small-capacity power consumption in the population areas, and to provide electricity locally for buildings that have conditionally established photovoltaic roofs. In the future development planning of the power grid, the impact of off-grid photovoltaic power generation and photovoltaic grid-connected power generation on the power grid and mathematical models should be fully considered for load forecasting. The off-grid PV system can be considered as an online active variable load model (herein referred to as the off-grid PV system in the city, but also the load supplied by the municipal grid). If photovoltaic grid-connected power generation systems are supplied with 110V or 220V grid-connected power, photovoltaic grid-connected power generation systems can also be considered as active load models that can change from negative to positive. Through the above analysis, the long-term positioning of photovoltaic grid-connected power can only serve as an important supplementary means for energy conservation and consumption reduction of the power grid. If it exceeds this strategic positioning, it will result in investment and additional energy waste, and the optimistic view on reducing pollution emissions will also be greatly reduced.
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