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With the continuous improvement of social economy, people's living standards are gradually improving, and the demand for electricity is also gradually increasing. Such demand has brought huge pressure to our country's power supply system. Although some new power generation energies are constantly being discovered, the uncontrollability of new energy power generation will have a great impact on the power quality in the power grid, so it is necessary to conduct further research on the power quality problems caused by the access of new energy sources In order to ensure the stable operation and reliability of the new energy power generation system. Therefore, the relevant departments and relevant staff should pay attention to the work research in this area.

The impact of new energy power generation on grid electricity

On the basis of new technologies, systematic utilization and development of renewable energy, such as nuclear energy, wind energy, solar energy, ocean energy, hydrogen energy, biomass energy, geothermal energy, etc. Unconventional energy usually refers to new energy in addition to traditional energy. Compared with fossil energy, new energy has two obvious advantages, one is that the amount of pollution is relatively small and the reserve is large, and the other is that new energy is recyclable and renewable. Since the 21st century, the extensive use of fossil energy has brought environmental pollution, energy depletion and climate change to society, and the development and progress of human society have been seriously challenged. However, renewable energy and new energy have entered an era of rapid development, and will definitely become the strategic direction of social development and a new force in the world energy system in the future. One of the key points of my country's future development is to master new energy technologies.

Due to the late development of my country's technology research on new energy power generation and certain limitations, the lack of stability in my country's use of new energy power generation is mainly manifested in strong discontinuity, volatility and randomness, and new energy The control technology of power generation is very difficult. At this stage, the capacity of the power grid to accept is still insufficient, and it is difficult to accept the power generation generated by new energy sources on a large scale, mainly in the following aspects:

(1) Influence of volatility and intermittent power generation

For wind power generation, the output power of the wind turbine is related to the wind speed. Since the wind energy is proportional to the cube of the wind speed, and the wind speed in nature is extremely unstable, it is difficult to artificially control the wind power, resulting in a large change in the output power of the wind turbine. For photovoltaic power generation, the output power of the photovoltaic array is related to the intensity of the light, so it is greatly affected by the weather and temperature, and it is prone to fluctuations like wind power generation. A large number of fluctuating wind power generation and photovoltaic power generation are integrated into the traditional power grid, which will cause the power grid to be subjected to huge current shocks, causing problems such as grid frequency deviation, voltage fluctuation and flicker. For example, when the voltage of the wind farm drops, if the wind turbine does not have the capability of low voltage ride-through, it is easy to cause an instant failure. Therefore, in order to avoid the occurrence of these situations, the new energy equipment integrated into the power grid is required to have the specified grid-connected technical performance, and secondly, the power grid needs to have sufficient peak shaving capacity and power receiving capacity. Among them, the most indispensable functions of new energy power generation system devices are active power adjustment and dynamic reactive power adjustment. In addition, reactive power losses are prone to occur in wind farms and photovoltaic power stations. Therefore, the functions of the configuration and application of new energy power generation systems also need to configure reactive power compensation functions.

(2) Influence of harmonics

In the new energy power generation system, there are two main ways to bring harmonics to the grid. Taking the wind power generation system as an example, one is that the power electronic device equipped with the wind turbine itself will bring about harmonic problems. For the constant-speed wind turbine directly connected to the grid, it needs to be connected to the grid through the power electronic device during the soft start phase, which will generate certain harmonics. For variable speed wind turbines, it is connected to the grid system through rectification and inverter devices. If the switching frequency of power electronic devices is within the range of harmonic generation, serious harmonic problems will occur; the other is wind power generation. The parallel compensation capacitor of the machine may resonate with the line reactance. In order to balance the reactive power on-site, the wind power generation system needs to be equipped with a parallel compensation device. However, due to the constantly changing harmonics and the complexity of the power grid, it may cause harmonic amplification and even system resonance under certain conditions.

Therefore, in a wind farm, the centralized connection of a single variable-speed or constant-speed wind turbine should be avoided as much as possible, which will cause excessive harmonic voltage locally, and a mixed configuration of different types of wind turbines should be used. Secondly, the power system should properly configure the filter device to reduce the harmonic content in the power grid, and use dynamic or static reactive power compensation devices reasonably while suppressing harmonics.

(3) The influence of the isolated network

When the large power grid loses voltage, the grid-connected wind power generation and photovoltaic power generation will continue to supply power to a certain part of the power grid, and form a connection with the local load to achieve a new balance of supply and demand, forming an isolated grid operation. At this time, the voltage and frequency in the isolated network are not controlled by the large power grid, and cannot be adjusted and supported by the large power grid. When the load on the load side changes or the output power on the generation side changes, the supply and demand of the isolated grid will be unbalanced, making the isolated grid unbalanced. The voltage and frequency of the device are prone to fluctuations. If the fluctuation range exceeds the allowable safety range, it will seriously affect the safety of the equipment. When the supply exceeds the demand, the voltage and frequency will exceed the allowable range, which may cause damage to the user's equipment. When the supply is less than the demand, the inverter will be overloaded and the inverter may be burned. Therefore, before new energy is integrated into the power grid, power dispatching must be strictly checked and reviewed. For wind power generation systems and photovoltaic power generation systems, having the power prediction function is one of the necessary access conditions.

(4) Influence of non-uniform grid-connection standards

The distribution of new energy sources is wide, but the distribution is not uniform enough. It is still difficult for our country to achieve a relatively unified grid connection standard for new energy power generation. According to my country's current technological development status, we can only unify the technical standards of those large-scale grid-connected systems, but not the testing technology, and there are certain defects in the system testing, so we should continue to further improve the system certification.

At this stage, my country lacks professional knowledge to analyze the main reasons that destroy the stability of the power system and reduce the power quality in the grid connection of large and medium-sized new energy sources, and even lack reasonable identification of the power grid dispatching and influencing factors affecting the power grid operation. Moreover, the problems existing in the power grid acceptance technology are still under constant research and exploration. At present, there is no real unified conclusion, and it is difficult to complete the perfect detection of my country's current technical capabilities for the access system. For example, the detection of inverters and controllers needs continuous improvement. In addition, although we are constantly developing and exploring the detection technology of power transmission and distribution equipment and two-way metering equipment, there is still a big gap between my country's technology and the technology of some western developed countries.