With the continuous acceleration of industrialization, the consumption of coal and oil resources is becoming more and more serious, and it has further aggravated the energy shortage of all countries in the world, and the large use of primary energy has brought great threats to people’s daily lives and produced very serious environmental pollution problems. Therefore, the development of renewable energy and its replacement of traditional energy sources has become a key concern of all countries. Solar energy is very widely distributed and is a renewable energy source. Photovoltaic power generation is the full use of solar energy to generate electricity, and this technology has also developed rapidly in recent years. With the proposal of China’s carbon peak and carbon neutrality goals, new energy sources such as wind power and photovoltaic power generation will usher in a new round of explosive growth, and the cumulative installed capacity of wind power and photovoltaic power generation will reach more than 2030.12 billion kilowatts in <>, so it will be crucial to build a new power system with new energy as the main body.
1. Photovoltaic grid-connected power generation system composition
The photovoltaic grid-connected power generation system is mainly composed of relay protection device, photovoltaic array, inverter, energy storage device and maximum power point tracking device. In order to ensure that the voltage and current are at the same frequency, the most basic link in the entire photovoltaic system is the photovoltaic array, which can use the photovoltaic array to convert solar energy into electrical energy, and then install it in series and parallel on the bracket through the battery cell according to the actual demand of voltage and current. However, the array of photovoltaic cells has a strong nonlinear characteristic, mainly due to the influence of load light and temperature in the process of power output.
The maximum power point tracking device can ensure that the maximum output power of the battery array is maintained at all times, ensuring that the efficient use of photovoltaic energy can be truly realized. The energy storage device is mainly to regulate and control the electric energy in the photovoltaic system, store sufficient electric energy in the lighting process, and release the stored electric energy when needed, which can effectively adjust the balance state of power supply and the output state of the power supply.
The inverter is mainly for the photovoltaic power generation system and the power grid for effective connection, through the inverter and transformer can convert direct current into AC power that can be used by people, but also an important part of the entire power generation system. The photovoltaic power generation system also has some very typical characteristics, that is, affected by factors such as external temperature and light, which will affect the output power, resulting in unstable power generation and controllability, and the cost of the entire photovoltaic system is very high. Therefore, to maximize the absorption andutilization of solar energy and control operating costs are the problems that relevant staff need to focus on. Only by effectively improving the active power rate of the photovoltaic power generation system and fundamentally improving the utilization rate of solar energy can we ensure that the grid-connected voltage and grid-connected voltage of the system are consistent.
2.1 Power quality
Photovoltaic power generation system in the daily operation process, is easily affected by external environmental factors, especially in rainy weather, because there are huge clouds in the air will block the sun, it will lead to a short period of time photovoltaic power power power will appear a large drop or rise, especially for large-scale photovoltaic power generation systems, but also the impact is very large, in a short period of time photovoltaic power generation system voltage is likely to appear flashing edge phenomenon, This leads to large frequency fluctuations in photovoltaic power generation systems. In addition, there is a part of the photovoltaic power generation system is the use of direct current for power generation, when connected to the power grid, if the inverter device method is selected, then it will further increase the harmonic problem, and the probability of occurrence will affect the normal operation of the photovoltaic power generation system.
2.2 System Protection
If the sunlight is very strong, the output power of the photovoltaic power generation system will further increase, which is likely to increase the short-circuit current, resulting in the phenomenon of overcurrent protection and mismatching, and even may affect the normal operation of the fuse, which will have a great impact on the entire photovoltaic power generation system. If the distribution network is not connected to the photovoltaic power generation system, in general, there is no unidirectional output protection for the branch power flow; After connecting to the photovoltaic power generation system, the distribution network becomes a multi-network network, and the network power flow will also have the characteristics of randomness, so the direction protection device must be installed in the photovoltaic power generation system.
2.3 Line currents
In the actual operation of the photovoltaic power grid, the branch power flow will generally have the characteristics of unidirectional flow, as the distance between it and the substation continues to extend, it will also lead to the monotonous reduction of the active power flow, but after the photovoltaic power supply is connected to the power grid, it will lead to the unpredictable characteristics of the entire power flow state, and the change of the power flow will further increase the difficulty of voltage adjustment of the photovoltaic power generation system, resulting in abnormal noise of the voltage adjustment equipment in the entire system. At the same time, the branch power flow may also be affected by this factor, and problems such as node voltage exceeding the limit and transformer container crossing the line may occur. Under such circumstances, the operation stability of the entire photovoltaic power generation system will also have a great impact. In addition, because the power flow is random, it can also have a great impact on the operation plan of the power plant.
3. Application of energy storage technology in photovoltaic grid-connected power generation
3.1 Power peak shaving
The most direct purpose of power peak shaving is to meet the power demand of concentrated and high-power during peak power hours, and effectively control the load of the power grid to the greatest extent. The energy storage device can be stored for the electric energy generated by the photovoltaic system according to the actual situation of the power grid operation, and then released during the peak period of electricity consumption, so as to ensure the output of the power peak power of the grid and ensure the reliability of the operation of the power supply system.
3.2 Load response
In the actual operation of the power system, in order to ensure the effectiveness of the power grid operation and minimize the probability of accidents, some large power loads are usually automatically adjusted, and different parts of the power grid will usually alternate in the state of high load, so as to ensure that the operation of the power grid during peak hours can meet people’s actual needs and ensure the stability of power supply. When power users use photovoltaic energy storage systems, they can maximize the stability of the user’s power supply, however, in this process, relevant staff should also focus on the connection between energy storage power stations and power grids in the load response system, and need to ensure that at least one communication line can operate normally, and the use of this way can avoid high-power equipment to the greatest extent and truly meet the response needs of the load. The use of load response technology in the photovoltaic power generation system, through the effective selection of different power grids for alternating applications, can reduce the probability of failure during the operation of the system, the use of response technology can make corresponding adjustments to high power loads, ensure stable work within the critical value range, ensure the quality of power supply, but also minimize the adverse impact on the stable operation of the power grid when adjusting the amount of power supply, to ensure the safe and stable operation of the power system. Maximum stability of power supply.
3.3 Power quality
During the operation of the photovoltaic power generation system, in order to fundamentally improve the power quality, it is necessary to ensure the scientific and reasonable application of energy storage technology. In the photovoltaic power generation system, through the reasonable application of energy storage technology, it can ensure that the performance of the photovoltaic power supply can be more stable during the actual operation process, and maximize the actual value of the photovoltaic power supply. In this process, the general staff will use a series of measures to inverter control the photovoltaic system, in the actual operation process, the power quality generated by the photovoltaic grid-connected power generation system can be effectively guaranteed, and the most critical role in the whole process is the energy storage control system. Using the application advantages of the energy storage system itself, it can not only effectively adjust the active filtering, but also better ensure the stability of the voltage, ensure that the phase angle is always within a reasonable range, and once the phase angle deviates, it can also be adjusted in time to ensure the quality of power supply.
For the transmission system, the integration of microgrids is the main trend of future development, and the reliability of power supply can be fundamentally improved through the use of microgrids. If the microgrid is separated from the entire power system, that is, the microgrid is in an island operation state, it can independently complete the power supply demand of the power load, and in this case, the use of photovoltaic power generation system to form a microgrid can also play its own role to ensure that the entire system power supply is safer and more reliable.
In the photovoltaic power generation system, the application of energy storage technology will involve all aspects, enterprises should also comply with the rapid development of the times, fully apply advanced Internet technology, properly deal with the application conditions of energy storage technology and specific influencing factors, try to eliminate the impact of the external environment, effectively improve the level of energy storage management of enterprises, through an effective incentive mechanism, establish a sound talent management system, in strict accordance with the principle of local conditions and overall planning. Establish a safer and more reliable photovoltaic grid-connected power generation system to provide people with more stable electric energy.