Currently, in order to achieve carbon reduction targets, the proportion of solar power generation in China is continuously increasing. To solve the problem of energy consumption, various regions have successively introduced policies related to energy storage. At the same time, with the continuous improvement of global electrification, “photovoltaic+energy storage” can also play a role in optimizing traditional power systems. “Photovoltaic+energy storage” can use solar power generation to reduce grid load during peak electricity consumption during the day, and can also store excess electricity during the day or during low electricity consumption periods at night to achieve peak shaving and valley filling to optimize local power supply.
(1) Policy changes
In 2021, the National Energy Administration issued energy storage related policies to support the use of “photovoltaic+energy storage” as an application of solar power generation and consumption, providing policy support for the development and application of “photovoltaic+energy storage”.
(2) Technological development
From large-scale centralized power plants to a combination of centralized and distributed spontaneous self use. Large centralized power plants generate electricity directly into the national power grid and connect to the high-voltage transmission and distribution system to provide long-distance power applications, thereby reducing costs and line transmission losses. The larger the scale of photovoltaic power plants, the lower the unit cost of the entire system. Spontaneous self use can reduce the construction cost and burden of the power grid, generate electricity locally, and consume locally.
The integration of photovoltaic power stations and user side energy storage is combined. Photovoltaic power stations will add energy storage links and integrate solar power generation, power supply, and energy storage regulation and control to quickly control and achieve maximum power output. Implement the “peak shaving and valley filling” function in response to power grid scheduling needs, ensuring real-time power grid scheduling needs. The use of energy storage systems can reduce the impact on the public power grid during grid connected power generation, and improve the quality of the power grid as much as possible. In addition, user side energy storage is installed in a distributed manner, which is flexible in construction and convenient for household users to promote.
Applying technologies such as big data, cloud computing, and cloud storage in the management of solar power plants. With the help of new information technology, real-time intelligent monitoring and analysis function management of the entire process of solar power generation can be achieved, improving the grid connection efficiency of solar power generation and reducing energy consumption. In order to comply with the development trend of the photovoltaic industry, relevant institutions in China are conducting comprehensive development of solar energy systems and collaborating with downstream equipment suppliers in the industry chain to jointly establish and operate intelligent energy equipment laboratories. The intelligent platform for photovoltaic power stations based on data mining technology closely integrates information technologies such as smart grids, cloud computing, and the Internet of Things, solving the problems of power optimization allocation and hierarchical control after integrating solar power generation systems with energy storage devices. Adopting a hierarchical multi-objective power regulation algorithm model for operational management of solar power generation and energy storage integrated systems. Through this platform, users can comprehensively and effectively grasp the information of the entire system, improve operational efficiency and decision-making response speed, and ensure the stable and safe operation of photovoltaic power plants. In the era of Industry 2.0, clean energy technologies, including solar power generation, and Internet of Things technologies are developing comprehensively. Through modern AI and big data analysis, different types of energy, including solar power generation, have been centrally managed and operated to create an intelligent energy ecosystem. With the development of the times, the future society will inevitably enter a low-carbon era and move towards building a new energy IoT system with more distinctive characteristics of the times.
The working principle of a solar inverter energy storage system operating off the grid is to transfer the electrical energy emitted by the solar photovoltaic panel to the battery for storage through a controller, and then the inverter converts the DC energy stored in the battery into AC energy for use by the terminal load. The efficiency, reliability, and power quality of power supply mainly depend on the performance of the solar charging controller and inverter. The main research content of this paper is as follows:
(1) Solar voltage reduction charging technology, in-depth analysis of synchronous voltage reduction rectification technology, and based on this, design a voltage reduction solar charging circuit and calculate the filtering inductance and capacitance according to the characteristics of solar charging. Based on the output characteristics of solar energy, research a solar charging controller with MPPT function and a charging management strategy for solar charging.
(2) Bidirectional DC isolation boost/boost converter technology is used to compare and analyze the working principles of DC boost circuit and DC step-down circuit, as well as the working principles of DC boost/boost circuit. Two full bridge circuits are combined with an intermediate isolation transformer to design a bidirectional DC isolation boost/boost converter.
(3) This paper introduces the working principles of the inverter mode and rectifier mode of the AC/DC bidirectional converter circuit and SPWM technology, and analyzes in detail the control method of SPWM technology, as well as the design method of the LC filter and key power devices of the AC/DC bidirectional converter.
(4) Design the overall structure, control circuit, sampling circuit, and system verification method of a household solar off grid inverter energy storage system. Detailed introduction is given to the overall structure of the household off grid inverter energy storage system composed of several modules, as well as the control circuit design of the three major electrical energy conversion parts. The sampling circuit of the system and the testing and verification method of the MPPT efficiency and inverter efficiency of the entire system are also designed.
(5) Simulation design of household solar off grid inverter energy storage system application, using PVsyst software to simulate the application of household solar off grid inverter energy storage system in design and daily life, analyzing the application effect of the system, and proposing the design method of solar off grid inverter energy storage project.
Mainly based on the functional classification of each unit module of the household inverter energy storage system, the solar voltage reduction charging circuit is analyzed based on the design process. The DC bidirectional voltage rise and fall conversion circuit and the AC/DC dual conversion circuit form a solar inverter energy storage integrated machine. The integrated machine is used as the core to simulate the household off grid inverter energy storage system using the PVsyst simulation platform, Finally, a design method for a household off grid inverter energy storage system is proposed.