With the continuous and rapid development of human technology, the required energy consumption has also gradually increased. Due to the current dependence of human energy mainly including oil, natural gas, coal, and nuclear energy, these consumable energy sources have gradually decreased with use, and raw material prices have also skyrocketed. Energy and economic crises have emerged, as shown in Figure 1, which reflects the current situation of China’s petrochemical energy reserves. Energy shortages in China may occur at any time. In addition, utilizing these consumable energy sources for power generation can also have direct or indirect impacts on the Earth’s environment, and even pose certain risks to humanity. For example, thermal power generation emits a large amount of carbon dioxide into the atmosphere, causing an increase in global average temperatures and water levels. Nuclear power generation is also subject to various natural and man-made disasters, such as the Chernobyl and Fukushima nuclear disasters, due to human negligence. In recent years, due to severe global climate change and rising anti nuclear awareness, advanced countries have actively sought various renewable energy sources such as solar energy, wind energy, tidal energy, geothermal energy, etc. to replace consumable energy. Therefore, research on renewable energy has been increasing rapidly. China has a vast territory, a large population, and a high demand for energy. It has enormous potential in the development of solar energy and is suitable for researching related technologies of solar energy, especially in the field of household use.
Human beings began researching solar power generation technology in the 19th century, based on the principle of photoelectric conversion, directly converting solar radiation energy into electrical energy. Solar power generation systems can be divided into off grid self use solar power generation systems (including various “photovoltaic+energy storage” power generation systems composed of solar inverters and energy storage batteries with off grid power supply) and solar power generation systems that feed into the grid by connecting to the public grid (which need to be connected to the public grid and send electricity to the grid through grid connected solar inverters).
The transition from traditional energy sources to new energy sources is crucial for achieving carbon neutrality goals, and “photovoltaic+energy storage” can play an important role. In the field of household solar power generation and energy storage, the application subjects include various types of end-users of household electricity. With the development of photovoltaic module manufacturing technology, the cost of solar power generation equipment is gradually decreasing, and the application scope is also gradually expanding. The “photovoltaic+energy storage” system can balance the electricity fees waived by installers with the system investment cost. At the same time, for installation, in some areas, “photovoltaic+energy storage” can also be chosen to solve the problem of insufficient grid coverage. Many residential areas in developed countries in Europe and America are independent residences, which are very suitable for building independent photovoltaic power generation and energy storage systems. According to census data from various regional statistical agencies, the proportion of independent/semi independent housing in developed regions such as Europe, the United States, Japan, and Australia exceeds 50%. The trend of large-scale development in the household energy storage market has shown that the industry as a whole is expected to continue to grow at a high level. In China, in order to fully leverage the role of electricity price leverage in guiding the optimization and allocation of power resources, promote green and low-carbon energy consumption, and improve the operational efficiency of the power system, the government has begun to implement peak valley time of use electricity pricing system for commercial and industrial users. The proposal of national policies has gradually highlighted the practical value of the “photovoltaic+energy storage” system in national economic life. The “photovoltaic+energy storage” system has the ability to spontaneously self use and stagger peak electricity consumption through energy storage batteries, which can make the actual electricity consumption more uniform in time distribution, reduce the grid electricity consumption, transformer capacity, and maximum required electricity consumption during peak periods, and simultaneously reduce electricity prices and basic electricity prices, To reduce carbon emissions and improve the efficiency of power grid operation. At present, China has implemented many plans and projects to develop and utilize solar energy. During the 13th Five Year Plan period of the country, a policy was formulated to simultaneously build centralized large-scale solar power plants and small distributed solar power plants. The installation of solar power generation in cities and residential areas is also relatively convenient and suitable for large-scale promotion and application.
The research on household solar off solar inverter energy storage system is aimed at distributed development and utilization of solar energy
Designed with broad application value.
Solar power generation systems have the following advantages compared to traditional power generation systems:
(1) Solar energy resources are very abundant, and solar radiation energy is endless. Therefore, the available power generation resources for solar power generation are the most abundant.
(2) Solar power generation is safer and more reliable, without incidental pollution and noise generation, and can operate safely and stably. The system can be flexibly configured according to actual applications.
(3) The application of solar power generation can more effectively solve the electricity consumption problem in areas without grid coverage, because solar energy resources are a type of energy that can be released in every corner of the world and obtained in every region.
(4) Solar power generation systems can be well integrated with buildings, saving land resources.
After entering the 21st century, the application of solar power generation technology has developed rapidly. From the perspective of power generation, the cost per watt of solar panels has been reduced from a dozen to a few pieces; From the perspective of energy storage, with the widespread application of electric vehicles, the cost of lithium batteries has decreased, and the secondary utilization of power batteries has made energy storage commercially valuable; At the same time, the advancement of power electronics technology and power device technology has attracted everyone’s attention to efficient and low-cost AC/DC conversion modules.
1. Current research status of household solar off solar inverter energy storage systems
The household off solar inverter energy storage system mainly consists of solar cell modules, off solar inverter energy storage integrated machine, and energy storage device, providing power supply for remote areas that cannot be covered by the urban power network. It includes solar household power supply, solar street lights, and other solar power generation systems with energy storage that can work independently. In order to make the system more adaptable to commercial applications, reduce system costs, and improve reliability, various institutions have done a lot of work from circuit architecture design, system simulation, and other aspects, including:
The solar photovoltaic charging controller focuses on the efficiency of the solar charging control system and MPPT of the solar charging controller in independent photovoltaic power generation applications, and studies the synchronous step-down charging circuit that adapts to the characteristics of solar charging and the charging management strategy of the solar charger battery; Design an algorithm for maximum solar power tracking efficiency that is compatible with the working mode of an independent solar photovoltaic charging control system; Modeling the working characteristics of solar photovoltaic panels and designing an MPPT algorithm model based on disturbance observation method; And comparative research on maximum power point tracking of photovoltaic panels using switching frequency modulation methods; Research on variable step size perturbation and observation algorithms for maximum power point tracking in photovoltaics; Utilize the characteristics of solar photovoltaic panels for simulation modeling and design MPPT algorithms suitable for various photovoltaic power generation systems.
A bidirectional DC converter is studied for solar power generation, which combines two modes: charging the battery and discharging the battery externally. This includes designing a model using full bridge soft switching technology to study the circuit for DC boost conversion in solar power generation; Research on autonomous DC voltage control for multi relaxation terminal DC microgrids; Research on modeling high-frequency isolation transformers in DC bidirectional converters.
Using MATLAB software to model and analyze the working status of the full bridge bidirectional converter in various modes; Research on the implementation of a home photovoltaic off solar inverter system using a half bridge LLC boost isolation circuit; Using predictive current control method, design an improved single-phase grid connected voltage source inverter with inverter inductor current as the control object; Design an energy storage bidirectional AC/DC conversion system that adapts to the charging and discharging characteristics of energy storage batteries based on their working characteristics; To solve the ground to ground RCD problem between solar photovoltaic panels and AC mains power, research on efficient and low leakage current single-phase transformer free bidirectional solar inverters; Design a single-phase bidirectional PEV charger for V2G reactive power operation for electric vehicle charging, energy storage, and grid connected power generation applications; Research on DC bus voltage regulation technology based on DC distribution system by combining single-phase bidirectional solar inverter with mains rectification and DC bus inverter application modes; Research on Modified Model Predictive Control of Bidirectional AC/DC Converter in Energy Storage Systems Based on Lyapunov Function.
Research on the control modes of solar inverter control all-in-one machine in various working states, as well as the application of combining inverter off grid working mode and grid connected working mode; Conduct relevant analysis on the conversion of control objects, switching between two modes, and compatibility of two mode filters in the system; Research on distributed power supply, energy storage, and related load monitoring and protection for microgrid systems, as well as energy allocation, system control, and protection energy management strategies for microgrid power supply systems.
Research on independent power supply for solar photovoltaic household inverter energy storage systems, using simulation design to assist in the application of household photovoltaic energy storage power supply systems under less than ideal environmental conditions, and combining smart grid application technology to analyze the characteristics of consumer energy consumption and household energy management to establish a household distributed energy storage and energy optimization utilization management system.
Through the analysis of the above research, it is found that the independent off grid solar photovoltaic power supply system combining solar power charging and storage technology, DC dual conversion technology, AC/DC dual conversion technology, etc., can achieve energy supply management and microgrid power quality control of decentralized power generation systems based on renewable energy, especially solar photovoltaic power generation, which is the development path of solar off solar inverter energy storage.
2. Research and development trends of household solar off solar inverter energy storage systems
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, achieve real-time intelligent monitoring and analysis function management of the entire process of solar power generation, and improve solar power generation
The efficiency of grid connection and utilization of electricity reduces 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.
3. Research content of household solar off solar inverter energy storage system
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 solar 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 solar 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 solar inverter energy storage system. Detailed introduction is given to the overall structure of the household off solar 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 solar inverter energy storage system application, using PVsyst software to simulate the application of household solar off solar inverter energy storage system in design and daily life, analyzing the application effect of the system, and proposing the design method of solar off solar inverter energy storage project.
Mainly based on the functional classification of each unit module of the household solar 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 solar inverter energy storage system using the PVsyst simulation platform, Finally, a design method for a household off solar inverter energy storage system is proposed.