Overview of distributed power (photovoltaic power generation) system
In the context of global warming and increasingly depleted fossil energy, the development and utilization of renewable energy has received increasing attention from the international community, and vigorously developing renewable energy has become the consensus of all countries in the world. The Paris Agreement came into effect on November 4, 2016, highlighting the determination of countries around the world to develop the renewable energy industry. General Secretary Xi Jinping has repeatedly emphasized that China adheres to the development concept of innovation, coordination, green, openness, and sharing, will vigorously promote green and low-carbon circular development, and take effective actions to address climate change, will peak CO2 emissions around 2030 and strive to achieve them as soon as possible. In 2030, CO2 emissions per unit of GDP will drop by 60%-65% compared to 2005, and non-fossil energy will account for about 20% of primary energy consumption. In order to achieve the above goals, it is imperative to develop renewable energy. Among all kinds of renewable energy, solar energy has become the fastest growing renewable energy because of its obvious advantages such as clean, safe, inexhaustible and inexhaustible. The development and utilization of solar energy is of great significance to adjusting the energy structure, promoting energy production and consumption, and promoting the construction of ecological civilization.
China is located in the Northern Hemisphere. Most areas are located south of 45°N latitude. Two-thirds of the country’s land area has more than 2,000 hours of sunshine. Among them, Tibet, Qinghai, Xinjiang, Gansu, Ningxia, and Inner Mongolia are all regions with rich solar energy resources. With the exception of the Sichuan Basin and Guizhou Province where solar energy resources are slightly poor, the eastern, southern and northern regions are also rich in solar energy resources. According to the number of hours of sunshine and the amount of radiation throughout the year, China’s solar energy resources can be divided into five categories, as shown in Figure 1.
The current ways of using solar energy are: distributed power (photovoltaic power generation), solar thermal utilization, solar power utilization, solar photochemical utilization, solar biological utilization and solar light utilization. In recent years, solar photovoltaic power generation has been rapidly developed around the world with its excellent characteristics, and is considered to be the most promising new energy technology in the world. Developed countries are competing to invest heavily in research and development, and actively promote the process of industrialization, vigorously explore the market application of solar photovoltaic power generation.
Working principle of distributed power (photovoltaic power generation) system
Distributed power generation (photovoltaic power generation) system is a system that uses photovoltaic modules and other auxiliary equipment to convert solar energy into electric energy. Its schematic diagram is shown in Figure 2, which is composed of photovoltaic modules, batteries, charge discharge controllers, inverters, etc.
During the day, under light conditions, solar cell modules generate a certain electromotive force. The solar cell array is formed through the series and parallel connection of the components, so that the voltage of the array can meet the requirements of the input voltage of the system, and then the battery is charged through the charge and discharge controller to store the electric energy converted from the light energy. At night, the battery pack provides input power for the inverter, which converts DC power into AC power through the inverter, and transmits it to the power distribution cabinet for power supply. The discharge of the battery pack is also controlled by the controller to ensure the normal use of the battery. The distributed power system also has limited load protection and grounding protection devices to protect the overload operation of the system equipment and avoid lightning strikes, and maintain the safe use of the system equipment.
Characteristics of distributed power (photovoltaic power generation) system
The unique characteristics of the distributed power (photovoltaic power generation) system determine its unique advantages and related constraints in the application.
1. Advantages of solar photovoltaic power generation system
(1) Safe and reliable;
(2) No noise and pollution;
(3) Sunlight is available everywhere, regardless of geographical restrictions;
(4) Does not consume resources;
(5) There is no need to set up long-distance transmission lines;
(6) The installation is simple and convenient, and the construction period is short;
(7) Decentralized construction and local power generation;
(8) Easy to implement step by step.
2. Disadvantages of photovoltaic power generation system
(1) Restricted by time period, geographic location, and meteorological conditions;
(2) Low light energy conversion efficiency;
(3) The initial investment is large.