Distributed photovoltaic power station usually refers to a small-scale power generation system with a small installed capacity that uses distributed resources and is arranged near users with the operation mode of user-side self-consumption and excess electricity being connected to the Internet. It is generally connected to a power grid with a voltage level of 35kV or lower. Distributed photovoltaic power generation follows the principles of adapting measures to local conditions, clean and efficient, decentralized layout and nearby utilization, making full use of local solar energy resources to replace and reduce fossil energy consumption.
At present, the most widely used distributed photovoltaic power generation system is the photovoltaic power generation project built on the roof of urban buildings. This type of project must be connected to the public grid, and together with the public grid, provide electricity to nearby users. Without the support of the public power grid, the distributed system cannot guarantee the reliability and quality of electricity consumption by users.
1. Development trend of distributed photovoltaic power stations
As a country with a large population, China’s land resources are extremely scarce. Therefore, the focus of distributed photovoltaic applications should not be based on ground power stations that occupy a large amount of land resources, but mainly in the form of applications combined with buildings, including applications on roofs, walls, and curtain walls of buildings. on the facade. Building integration of photovoltaics should be the focus of distributed photovoltaic applications.
Looking at the industrial environment and development trends of various countries, both the industry and the government have realized that the development of distributed photovoltaic power generation is the key to starting the market, digesting production capacity, realizing strategic transformation and driving the entire photovoltaic industry.
(1) Distributed focus is the focus of photovoltaic building and photovoltaic building integrated applications, which should be the roof with the best sunlight. According to the properties of the roof, the roof photovoltaic building integration application is divided into three categories: roof photovoltaic applications for industrial and commercial enterprises, public roof photovoltaic applications such as governments and schools, and residential roof photovoltaic applications.
From an investment point of view, an important principle for rooftop photovoltaic applications is to encourage “spontaneous self-use and surplus electricity to be connected to the Internet”. Therefore, the quality of rooftop photovoltaic power generation by rooftop owners affects its return on investment and safety.
For the roofs of industrial and commercial enterprises, due to the differences in the operating conditions of the enterprises themselves, enterprises with high energy consumption, high electricity prices and strong sustainable operation ability are most suitable for the implementation of rooftop power generation projects.
As for public buildings and residential roofs, due to the low level of electricity prices, they are basically in a blank state of development. From the perspective of development space, this is a blue ocean. Moreover, due to the continuous and stable energy consumption of public buildings and residential buildings, the return on investment will be relatively more stable if appropriate policies and relevant marginal conditions are defined. Therefore, from this perspective, public buildings and residential roofs should become the top priority of photovoltaic building integration applications, including photovoltaic power generation into homes and communities, sending photovoltaics to the countryside and villages, etc., and the space is huge.
(2) Incentive policies should be superimposed Due to the policy of “self-generated and self-consumption, surplus electricity connected to the Internet”, the average electricity price level corresponding to the photovoltaic power generation time has become the main factor affecting the economy and promotion of rooftop photovoltaic projects.
(3)At present, the average daytime electricity price for commercial electricity in China is generally maintained at 0.7-1.0 yuan/(kW·h). , whether it is for self-use or selling electricity, each kW·h electricity is subsidized by 0.42 yuan. This type of project has considerable economic feasibility. If coupled with the supporting policy incentives of various local governments, it is relatively easy to promote.
The average daytime electricity price level of public buildings and residential roofs is generally maintained at 0.48-0.6 yuan/(kW·h), among which rural residential electricity prices are the lowest. Even with distributed photovoltaic grid-connected electricity subsidies, the benefits of such projects are also low. . If you use photovoltaic building integrated materials, such as solar photovoltaic tiles and other products (such products need to have the dual properties of building materials and power generation equipment, the performance requirements such as quality, materials and aesthetics are higher, and the production cost is generally higher than that of ordinary photovoltaics. components are higher), resulting in a relatively poor economic viability of this type of roofing project.
Governments at all levels promote “Photovoltaic Building Integration Demonstration Project”, “Distributed Photovoltaic Power Generation Concentrated Demonstration Area”, “Renewable Energy Demonstration Town”, “Energy Saving and Emission Reduction Demonstration Town”, “Green Building Demonstration Town” and “New Building Demonstration Town” in combination with policies. The reform of projects such as “Energy Demonstration Towns”, considering energy conservation and emission reduction, low-carbon environmental protection, expanding investment, stimulating domestic demand, increasing farmers’ income, supporting and stimulating the photovoltaic industry, photovoltaics entering the community, going to the countryside and entering the village, ecological civilization construction and beautiful China Construction is the main purpose, focusing on the utilization of roof space in the new round of urbanization, focusing on encouraging the combined application of photovoltaic buildings, adopting the combination of government management guidance and fiscal policy encouragement, and comprehensively using fiscal policy, planning approval, energy assessment and Environmental assessment and other means to implement and start a national demonstration project of photovoltaic building integration application.
From the perspective of the development trend of photovoltaic applications, the future of photovoltaic application development is “one high and three lows”.
“One high” refers to materials with high photoelectric conversion efficiency. If the photoelectric conversion efficiency of the material reaches 25%, it means that the cost of photovoltaic power generation within China is between 0.3 and 0.5 yuan/(kW h), and every household will be Consider installing rooftop photovoltaics.
“Three lows” means that the terminal application of photovoltaic products should conform to three principles, namely, low space resource cost, low power transmission and transformation cost, and low installation, use and maintenance cost. The use of rooftop photovoltaics by households is the most in line with these three principles. To meet “one high and three low”, it will become a common trend for every household to build their own houses with photovoltaic tiles and photovoltaic curtain walls.
Therefore, no matter from which point of view, we should focus on encouraging the application of photovoltaic building integration, and give policy support and direction encouragement, then China’s photovoltaic industry will truly occupy the strategic commanding heights of the global industrial chain division of labor, and it will also truly play a role in Strategic role in economic transformation.
2. The impact of distributed photovoltaic power stations on the existing power grid
1) Impact on grid planning. The grid connection of distributed photovoltaics increases the difficulty of load forecasting in the region where it is located, and changes the existing load growth model. The access of a large number of distributed power sources makes the transformation and management of the distribution network more complicated.
2) Different grid connection methods have different impacts. Distributed photovoltaics operating off-grid have no impact on the power grid; distributed photovoltaics that are connected to the grid but do not transmit power to the grid will cause voltage fluctuations; grid-connected methods that transmit power to the grid will cause voltage fluctuations and affect relay protection. Configuration.
3) Impact on power quality. The important impact of distributed photovoltaic access is to change the voltage distribution on the feeder, and the magnitude of the impact is closely related to the access capacity and access location. Photovoltaic power generation is generally connected to the grid through inverters, and the frequent switching on and off of such power electronic devices is prone to harmonic pollution.
4) Influence on relay protection. Most of China’s distribution networks have a single-power radial structure, and most of them adopt the form of quick-break and time-limited quick-break protection, which is not directional. After the distributed power supply is connected to the distribution network, its injected power will reduce the scope of relay protection, and the entire line cannot be reliably protected. Even when other parallel branches fail, the relay protection of the installed distributed photovoltaic system may malfunction. .