The development prospect of photovoltaic power generation
Energy is an important material basis necessary for the development of the national economy and people’s lives, and it is also the driving force for promoting social and economic development and improving people’s living standards. The application of various new energies such as wind energy, wind energy, solar energy and so on all reflect the light of human wisdom. The transformation of energy is often driven by the needs of social production and development, and the revolution of energy production and consumption in turn promotes the leap of social productivity. With the comprehensive development of global industrialization, the demand for energy in various countries and industries has expanded rapidly, and the quality and quantity of energy demand has become the standard to measure the economic development of a country or region.
However, with the increasing demand for energy by human beings, the reserves of fossil energy are depleting. The Swiss Bank recently released a report that the world has proven oil reserves of 1.8 trillion barrels. According to the existing oil consumption level, the world’s oil can still be After 46 years of exploitation, half a century later, the oil and natural gas on the earth will be exhausted, and after 200 years there will be nothing to recover. In China, this situation is not optimistic. According to statistics, the oil consumption in 2014 reached 519 million According to experts’ forecast, by 2020, China’s oil consumption will exceed 700 million tons. More than 69% will depend on imports, and China’s coal consumption will be the highest in 2014. For the first time since the century, the decline was about 2.8%, but the consumption still reached 3.51 billion tons, exceeding 50% of the total global consumption. Coming around 2020, the demand for natural gas will reach 400 billion cubic meters, while the global demand will reach 4 trillion cubic meters. The exploitation, transportation and use of fossil energy will cause serious damage to the air and human living environment. At the same time, the large-scale emission of greenhouse gases makes the surface temperature of the earth rise year by year. If the global CO2 emissions are not controlled, the greenhouse effect will melt the icebergs in the south and north poles. This may cause the sea level to rise by several meters. One of the human living space will be greatly threatened.
In view of the above situation, the development and utilization of renewable energy and various green energy sources to achieve sustainable development has become a measure that human society must take. Environmental protection has long been mentioned on the agenda of the United Nations and governments at all levels, and stipulates that every June The 5th became the World Environmental Protection Day. Environmental protection slogans such as “There is only one earth in the world”, “The earth is your common home” and “Let the earth be full of life” fully reflect the common aspiration of all mankind. Renewable energy mainly includes water energy, solar energy, Energy forms such as wind energy, geothermal energy, biomass energy, etc., their greatest feature is their self-recovery ability. In the process of people’s use, renewable energy can be continuously supplemented from nature. They are inexhaustible and can be used for Unscrupulous energy, hydropower is currently the
The most widely used renewable energy, but it is greatly affected by geographical conditions, weather and climate, and the scope of use is limited.
According to the renewable energy development goals of various countries in the world and the current actual progress, experts predict that by 2050, the proportion of renewable energy in the total primary energy will be about 54%, and the proportion of solar energy in the primary energy will be about 13%~ 15%, by 2100, renewable energy will account for 86%, solar energy will account for 67%, of which solar power will account for 64%.
After research and demonstration by scholars, it is generally believed that solar energy and wind energy are the most effective and feasible energy types to solve the energy crisis and environmental pollution, and are the most important energy types in the new century, especially the application of solar energy and photovoltaic power generation. Its unique advantages attract more and more people’s attention
①The solar energy is inexhaustible and misused, enough to supply the earth’s human beings for billions of years;
②The application area of solar energy is wide, and the value of use in rural areas, islands and remote areas is higher. Solar energy is clean, and there is no pollution in the process of development and utilization;
③The solar photovoltaic power station Lecha has a simple design and a short construction and installation period
④Solar photovoltaic power generation has no moving parts, no noise, not easy to be damaged, and easy to maintain
Research status and development of foreign photovoltaic power generation
The limitation of fossil energy and the increasing pressure on environmental protection have made many countries in the world strengthen their support for green energy and renewable energy technology research. In the early stage of the development of photovoltaic power generation industry, it mainly relied on the strong support of governments in terms of policies and funds. , and now it has been gradually commercialized and entered a new stage of development. The involvement of many large companies has greatly accelerated the process of industrialization. Since the 1990s, developed countries have set off an upsurge in the development of “rooftop photovoltaic power generation systems”. The rooftop photovoltaic power generation system does not occupy a separate area. The solar cells are installed on the ready-made roof, which is very suitable for the characteristics of low solar energy density. Moreover, its flexibility and economy are much better than large-scale photovoltaic grid-connected power generation, which is conducive to popularization, combat readiness and energy security. “10,000 Solar Roofs Plan”, plans to install 1 million solar roofs by 2010, and some other developed countries also have similar photovoltaic rooftop power generation projects or plans, such as the Netherlands, Switzerland, Finland, Austria, the United Kingdom, Canada, etc. China’s India also announced in December 1997 that 500,000 solar rooftop power generation systems would be built by 2020.
In 2014, 38.7GW of new solar photovoltaic power generation was added in the world. The cumulative installed capacity reached 177GW. The cumulative installed photovoltaic capacity in 2014 was about 10 times the cumulative installed capacity of photovoltaics in 2008, and the annual photovoltaic power generation accounted for 1% of the total global electricity consumption. Among them, the photovoltaic power generation in 19 countries accounts for more than 1% of the country’s total power consumption. The three countries with the highest photovoltaic power generation are Italy with 7.9%, Greece with 7.6%, and Germany with 7.0%.
It is expected that the production of photovoltaic modules will develop at an annual growth rate of 20% to 30% or even higher in the next 10 years. It is estimated that by 2050, solar photovoltaic power generation will reach 110% to 20% of the world’s total power generation, becoming the basis for human beings. one of the energy sources.
For photovoltaic power generation technology, the latest international research and development hotspots mainly focus on low-cost, high-efficiency photovoltaic panels, high-efficiency, high-stability inverter equipment, and photovoltaic building integrated application systems. The optimal configuration between photovoltaic panels, inverter equipment and monitoring and management systems is also the key to photovoltaic system research, which involves a number of technologies. The United States, Germany, the Netherlands, Japan, Australia and other countries are motivated by the photovoltaic exhibition top plan. Companies and research institutes have successfully launched a variety of different high-performance inverters. The power generation efficiency of solar cells is constantly improving. With the advancement of technology and the expansion of production, the cost of photovoltaic power generation systems is also decreasing. In the past 8 years, the price of photovoltaic modules has dropped by 89%, the price of the system has dropped by 87%, and the price of photovoltaic electricity has dropped by 80%. , Photovoltaic inverter device is another key equipment of photovoltaic power generation system. The internationally famous photovoltaic inverter companies mainly include SMA in Germany, Power-ONE in the United States, Emerson, KACO in Germany, REFUsol in Germany, and Fro-nius in Austria. Siemens in Germany, Danfoss in Denmark, etc., still occupy certain advantages in terms of market share, inverter efficiency, and reliability.
Development of photovoltaic grid-connected inverter technology
As an interface device between photovoltaic cells and the power grid, the grid-connected inverter converts the electrical energy of the photovoltaic cells into AC power and transmits it to the power grid. It plays a vital role in the photovoltaic grid-connected power generation system. Modern inverter technology is photovoltaic The development of grid-connected power generation provides strong technical and theoretical support.
The improvement of the performance of the grid-connected inverter is very important to improve the efficiency, reliability, prolong life and reduce cost of the system. The development of inverter technology has always been closely integrated with the development of power devices and its control technology. five stages. The first stage: in the 1950s and 1960s, the birth of the thyristor SCR created conditions for the development of the sine wave inverter; the second stage: in the 1970s, the turn-off thyristor GTO and the bipolar transistor BIT came out, The development and application of inverter technology: The third stage: In the 1980s, the birth of power field effect transistors, insulated gate transistors, MOS control thyristors and other power devices
The fourth stage: in the 1990s, the development of microelectronics technology enabled recent control technologies such as vector control technology, multi-level conversion technology, repetitive control, fuzzy control and other technologies. It has been well applied in the field of inverter, which has greatly promoted the development of inverter technology; the fifth stage: at the beginning of the 21st century, with the continuous improvement of power electronics technology, microelectronic technology and modern control theory, inverter technology Technology is developing in the direction of high frequency, high efficiency, high power density, high reliability and intelligence.
Including photovoltaic grid-connected inverters, China’s photovoltaic cell power generation industry chain is relatively complete. Since the 1980s, the research and development of photovoltaic inverters has been carried out, and there are special companies that research and develop grid-connected inverters. Due to the late start-up time of the terminal market, Chinese photovoltaic inverter manufacturers are generally small in scale, and there is a certain gap between the structure, technology, workmanship, conversion efficiency, degree of intelligence and stability and other indicators of first-class foreign companies. In recent years, driven by the international photovoltaic market and the domestic Golden Sun demonstration project, a group of photovoltaic grid-connected inverter companies represented by Hefei Sungrow, a leading enterprise that once occupied more than 60% of the domestic market, have developed rapidly and have entered the to the European market and other high-power markets abroad. In addition to Hefei Sunshine, in the high-power power station inverter market, there are mainly companies such as Beijing Kenuo Technology Co., Ltd. and TBEA.
Research hotspots of photovoltaic grid-connected inverter technology
Under normal circumstances, grid-connected inverters are divided into two types: single-phase and three-phase according to the number of output phases. The output power of single-phase grid-connected inverters is small, generally not exceeding 15KW. Therefore, it is suitable for small and medium power grid-connected power generation systems. The three-phase method is mostly used in high-power energy conversion occasions. If it comes according to the output power value, there are mainly four types of micro-inverters, low-power inverters, medium-power inverters and high-power inverters. At present, the most mature and fastest developing technology is the medium-power grid-connected inverter, which has been widely used. Micro-inverters and high-power grid-connected inverters will gain broader market prospects. Micro-inverters are mostly used in residential electrical charging systems, while high-power photovoltaic grid-connected inverters have large-capacity power output. Therefore, it is very suitable for photovoltaic power plant systems. With the rapid development of the photovoltaic industry, grid-friendly inverters with large capacity, high efficiency and strong reliability will become the focus of research. To realize the inverter with high efficiency and low current distortion rate, it is necessary to analyze and study from the following aspects.