There are many important factors that humans rely on for survival and technological progress, among which the most important are material, energy, and information. There have been many revolutionary changes in the way energy is used in history, and each change in energy usage has greatly promoted the development of modern civilization. The first industrial revolution was triggered by the steam engine, thus humanity entered the era of machines; The Second Industrial Revolution was triggered by electricity, and the invention and utilization of electricity brought humanity into the electrical age; The third industrial revolution was also due to the invention of semiconductors, and since then, humanity has entered the information age.
At present, the new energy industry has entered a flourishing era, which can also be said to have triggered the world’s fourth industrial revolution. In China, the government also attaches great importance to new energy generation, including wind power generation, biomass power generation, solar radiation power generation, hydrogen power generation, and hydropower power generation, and has also focused on the development of renewable energy. In 2007, the National Development and Reform Commission officially released the Medium – and Long Term Development Plan for Renewable Energy, and in 2008, the Eleventh Five Year Plan for Renewable Energy Development was also released.
Human survival and social development cannot be achieved without energy. At the same time, energy also controls the economic lifeline of world development. Moreover, national security is closely related to the development of new energy. With the development of science, technology, and social economy, people’s economic income and spiritual life are also constantly improving, so the demand for material energy is also constantly increasing. In the current world energy use structure, coal, natural gas, oil and other primary energy still occupy the main position, but the limited energy reserves have been increasingly exhausted. After the 21st century, human material civilization has reached its peak from ancient times to the present. If we want to maintain or continue to promote development, the energy problem is currently a major challenge that continues to be solved.
Solving energy issues not only promotes social progress, but also reduces the enormous burden on the Earth’s environment caused by large-scale mining and the use of primary energy. The extensive use of primary energy has led to the emission of approximately 100 million tons of greenhouse gases such as CO2 into the air, resulting in severe air pollution. This not only poses a challenge to sustainable economic and social development for humanity, but also poses a huge challenge to the environment on which it relies for survival. The progress and development of society have become a contradiction with the environment in which humans live. The environment needs to be protected, and society needs to progress. Under this dual constraint, only new energy is the fulcrum of this lever. Sustainable development can promote social progress and ensure that the environment does not deteriorate. Therefore, large-scale development and utilization of renewable clean energy can solve the contradiction between social development and the environment today.
The sun is an inexhaustible renewable energy base, with enormous and long-lasting energy. The utilization of solar energy can be mainly divided into two ways: photothermal and photovoltaic power generation. The photovoltaic effect occurs when sunlight shines on semiconductor materials, converting solar radiation into electrical energy. This type of power generation method is called photovoltaic power generation. Photovoltaic power generation plays a crucial role in the development and utilization of solar energy, with the value of large-scale development and many advantages.
The development and utilization of solar energy is currently an effective means to solve the depletion of conventional energy, which can not only achieve sustainable energy development but also improve the living environment. The core part of the entire process of solar power generation is the solar inverter, which is the heart of the power generation system and an indispensable part. Its quality determines the operational efficiency and power quality of the system.
The market space for photovoltaic power generation systems is very broad, with a wide range of application prospects. Its development will also become a major trend that affects the world, and every country will focus on researching and developing it.
In 1973, the United States passed and formulated a photovoltaic power generation development plan, which established the country’s own short-term, medium, and long-term development strategic goals. In 1974, Japan invested $500 million in the “Sunshine Program”, which brought its country to the world’s leading level in solar cell production. After the 1980s, many Western countries also began to invest funds to enhance the technology and industrialization process in their development plans. In the 1990s, many developed countries also joined the grid connected solar photovoltaic rooftop plan, which combines the idea of combining solar energy technology with architecture.
In 1990, Germany implemented the “1000 Roof Plan”, which later developed into the “2000 Roof Plan”. This plan has always been funded by the government, and with the support of power companies, the photovoltaic grid connected residential roof system has been successfully constructed. By 1997, the number of completed photovoltaic modules had exceeded 10000, with each set costing approximately 1-5 kW, resulting in a total installed photovoltaic module of 33 MW.
After the Kyoto Conference held in Japan in December 1997, the President of the United States announced a 1 million photovoltaic roof plan, with an expected installation of 3GW of photovoltaic roofs within 10 years. The global photovoltaic industry experienced a relatively high growth rate from 1997 to 2001, with an average growth rate of 35.5%. In 2003, the production of photovoltaic cell modules was approximately 744.26MW, but the following year it reached 1194MW with a growth rate of 60.46%.
By the end of 2004, the installed capacity of photovoltaic power generation in the world had accumulated to 4330MW. From a global perspective, the initial development of photovoltaic power generation technology has been completed and is in the demonstration stage of development. The current development direction is mass production and scale utilization. Photovoltaic power generation has been used as a power source for low-power appliances since its inception, and now it is connected to the grid for use by thousands of households and large factories. Its application fields should involve various industries. It is expected that in the 1950s, photovoltaic power generation will be one of the main forms of human energy acquisition, accounting for 10% to 20% of the world’s energy.
In 1958, China began to devote itself to the research of solar cells and successfully applied them on the Dongfanghong-2 satellite launched in 1971. In recent years, under the high attention of the government, poverty alleviation projects based on photovoltaic installation and power generation subsidy policies have been successfully implemented, leading to a rapid increase in China’s photovoltaic installation volume. The newly added installed capacity in 2017 increased by 51% compared to last year, reaching 52.2GW, of which distributed is expected to add 18.57GW, a significant increase of 33.8% compared to 2016.
Between 2015 and 2017, the annual compound growth rate of newly added photovoltaic installed capacity in China was around 70%, while the installed capacity of distributed photovoltaics rapidly increased between 2016 and 2017, with year-on-year growth rates of 205% and 338%, respectively. Especially in 2017, it accounted for 35.65% of the total newly added photovoltaic installed capacity, and distributed photovoltaics are expected to exceed half in 2018; If calculated at a growth rate of 40%, the newly added photovoltaic installed capacity will reach 73GW in 2018, of which approximately 36.5GW will be distributed photovoltaic installed capacity, with a year-on-year growth rate of around 100%. Under the strong promotion of the photovoltaic industry by the government and enterprises in the past year (2017), this industry has been able to develop rapidly, ultimately achieving the goal of comprehensive popularization.
The expected new photovoltaic installed capacity in 2017 is about 53GW, with a year-on-year growth of over 46%. It has been the fifth year since it ranked first in the global annual new market and the third year since it held the top position in the global market, with approximately 130GW. The expected installed capacity of distributed photovoltaics in 2017 will exceed 18GW, with a year-on-year growth of 300% or more. It is expected that the installed capacity of household photovoltaics will exceed 500000 households in 2017, with an installed capacity exceeding 2GW. Especially noteworthy, outdoor photovoltaics are rapidly emerging. With the development of the photovoltaic industry in China, indispensable solar inverters are also constantly joining the ranks of rapid development.
At the end of 2017, the Notice on Issuing the First Batch of Photovoltaic Poverty Alleviation Project Plans for the 13th Five Year Plan was jointly issued by the National Energy Administration and the Poverty Alleviation Office of the State Council. The first batch of photovoltaic poverty alleviation projects for the 13th Five Year Plan was officially issued. This batch has issued 14 provinces, municipalities, and autonomous regions, and the number of key poverty alleviation counties has reached 236, with a total installed capacity of 4.186GW.
According to data analysis, in the newly added photovoltaic market, the development scale of distributed photovoltaics is particularly strong, and its proportion is gradually increasing, jumping from 12% to 36%. Staff from relevant research institutions pointed out that in 2018, distributed photovoltaics will collectively surpass ground power stations in terms of growth rate and new installed capacity. In addition, the documents issued by the two ministries at the beginning of the year have raised high expectations in the industry for the promotion of the pilot of distributed transactions, and the industry is also increasingly looking forward to it.
The purpose is to implement the hardware of household solar inverters, which mainly work in the following aspects:
(1) Analyze and study the topology, basic components, and control principles of the main circuit of solar inverters. Study the output characteristics of solar panels. For solar inverters, in order to achieve efficient and reliable operation, the main topology and maximum power tracking control of photovoltaic cells are crucial. Therefore, in response to the content of this paper, a two-level household solar inverter main topology structure is designed, which can meet the basic requirements of off grid and grid connected operation. The disturbance observation method is used as the maximum power point tracking control method for solar cells in this design.
(2) Design the hardware circuit and software control process of a household solar inverter based on K60. The hardware circuit mainly consists of the embedded microcontroller core board module, power module, voltage and current detection module, and auxiliary power module. The software control process mainly includes the main program, maximum power point tracking program, frequency and phase control program, and system protection subroutine.
(3) Simulation research on maximum power point tracking control strategy based on disturbance observation method. Design a photovoltaic panel model, two SPWM generators, and a solar inverter model for off grid operation in the MATLAB/Simulink software environment. Perform system simulation on the established model to verify the correctness of system modeling and design.
(4) Finally, based on the above analysis results, a prototype of a household solar inverter based on K60 control was developed using an experimental platform. The circuit board schematic and PCB diagram were drawn using Altium Designer software, and the designed circuit board was processed, soldered, and debugged. Program the embedded microcontroller K60 using C language for software debugging, provide relevant experimental results, and verify whether the system can achieve the expected results.
Firstly, the background and significance of the topic of designing household solar inverters based on K60 were briefly described. The research status and development trends of household solar inverter design at home and abroad were briefly discussed, and the main research content of this article was listed. The specific research direction of this graduation project was clarified.