With the increasingly severe energy and environmental issues worldwide, the importance and necessity of renewable energy extraction and use are becoming increasingly prominent, and renewable energy will undoubtedly be the focus of future energy wars. Based on the current rate of human energy consumption and the utilization rate of primary energy, fossil fuels will be completely consumed by humans in the future. In addition, due to the combustion of fossil fuels, a large amount of harmful gases and dust particles are discharged into the air every year. The emitted CO2 can cause a global greenhouse effect, and harmful gases such as SO2 and NO2 can lead to acid rain and damage the Earth’s environment. Due to the influence of climate and geography, hydroelectric, geothermal, tidal and other power generation can sometimes disrupt the local ecological balance; For nuclear power, the development prospects are bright, but the technical requirements for nuclear power generation are very high. Once a nuclear leak occurs, the consequences are very serious (such as the Chernobyl nuclear leak in the former Soviet Union and the nuclear leak caused by the 2011 Japan earthquake, which brought great harm to society and could not be eliminated for decades or even centuries), and the disposal of nuclear waste is also difficult to solve. Based on the above situation, it is urgent for people to seek new energy sources to replace primary energy. Solar energy has become an important part of future renewable energy development due to its infinite quantity, wide geographical coverage, and clean usage. To better and comprehensively utilize solar energy, solar photovoltaic grid connected power generation systems are currently and even for a long time in the future the best choice. The solar photovoltaic grid connected inverter technology, as the core technology of the photovoltaic grid connected power generation system, is one of the important factors that determine the efficiency of the photovoltaic grid connected power generation system, and is also the most important factor restricting the development of the photovoltaic industry at present. Therefore, in-depth learning and innovative design of solar photovoltaic grid connected inverters have significant practical significance.
1. Current research status of solar photovoltaic inverters abroad
Nowadays, the development of grid connected inverter technology is relatively mature in foreign countries, and a relatively mature product series has been established, such as solar inverter products such as SMA, Fronius, Sun Power, Sputnik, and Siemens, which are commonly used in Western countries today. Among them, SMA has the largest market share, accounting for about 50%. However, in addition to some European countries, the United States, Canada, Australia, New Zealand, and Japan also have their own relatively mature and complete product lines. Next, this article will use some mature solar photovoltaic inverter products as typical examples to explain the research situation of foreign transformers.
Among SMA’s products, branch solar inverters and multi branch inverters are relatively more commonly used. These two solar inverters have the following advantages: high efficiency, advanced and mature SMA inverter technology, and have done well in this regard; Low THD; The power factor of the two solar inverters is very high; Another aspect is maximum power tracking, which directly determines the efficiency and stability of solar inverters. Both solar inverters are implemented using software; In actual operation, these two solar inverters of SMA have intelligent adjustment links, making the system more perfect, and their main working status is displayed more intuitively with LED; Having the advantage of self diagnosis; Many products can be freely combined in series or parallel, providing more options for system construction and facilitating future expansion.
Compared to SMA, Siemens products have significant differences in structure, with most of their structures being master-slave. This form of solar inverter system is relatively rigid and cannot catch up with SMA’s products in terms of system scalability. The SITOPSolar is a well-known and widely used product among Siemens. The composition structure of SITOPSolar is also very unique, which includes two branch solar inverters, namely isolated and non isolated. The internal integration method of SITOPSolar is different from that of SMA products. Its maximum power tracking unit does not exist alone, and there is also an inverter unit in the chassis where it is located.
In addition to the above products, the United States has also launched Xantrex for the Sun Rail XR series based on market demand. The scope of grid connected solar inverters basically covers the ability and high power, and can also be a system composed of multiple solar inverters in parallel. At the same time, the link of the solar inverter MPPT will also be integrated inside.
2. Current research status of solar photovoltaic inverters in China
China is gradually increasing its research and investment in solar photovoltaic grid connected inverters, striving to catch up or even surpass European countries in technology. At present, the focus of our country’s learning and research is on one is the maximum power tracking method, and the other is the energy transformation layout of the inverter part. In terms of commercial operation practice, China’s solar power generation system and related industries still have a long way to go. The vast majority of existing photovoltaic projects in China still rely on introducing solar photovoltaic inverters from abroad or obtaining them through collaborative research, which inevitably restricts the Chinese photovoltaic industry and makes it more difficult to promote.
At present, the shortage of energy in China and the sustainable development of energy have affected the healthy development of the economy and society. From this, we can see that photovoltaic power generation will become an effective way to solve the problem of energy shortage, and its development will have a bright future. If photovoltaic power generation is to expand into the electricity and construction markets, the development of grid connected photovoltaic power generation is essential. Only when the application scale of photovoltaic power generation reaches the power scale can China’s energy shortage and environmental pollution be alleviated.
Solar grid connected inverters are important components that connect solar panels to the power grid and play a crucial role in the system. With the gradual development of solar power generation systems, solar inverters, as the core part of the system, are gradually becoming the focus of attention. High efficiency, high reliability and other technical issues have been increasingly valued, and have become the key to the success of solar grid connected inverters in the future. These improvements of solar grid connected inverters provide a guarantee for improving system efficiency, lifespan, reliability, and reducing system costs. They will play an irreplaceable role in the entire photovoltaic power generation system. So the most basic and critical technology to achieve photovoltaic power generation is solar photovoltaic inverter technology. However, China’s solar inverter technology is relatively backward, and it is necessary to introduce solar grid connected inverters from abroad, which makes the cost of the system too high and the implementation and promotion of the system more difficult. In order to independently develop effective products, large domestic enterprises have begun to collaborate with domestic universities to research photovoltaic power generation related technologies. Currently, China’s power generation technology has not yet been industrialized and is still at the level of demonstration systems, requiring further development. In order to make photovoltaic power generation popular, we need to vigorously independently develop the solar grid connected inverter, which also has rich practical significance.