The impact of new energy generation grid-connected on grid power

The impact of new energy generation grid-connected on grid power

Based on emerging technologies, our system harnesses and advances renewable energy sources such as nuclear energy, wind energy, solar energy, ocean energy, hydrogen energy, biomass energy, geothermal energy, and more. These unconventional energy sources are commonly known as new energy sources, distinct from traditional energy sources. Compared to fossil fuels, new energy offers two significant advantages. Firstly, it generates fewer pollutants and boasts ample reserves. Secondly, new energy sources are renewable and recyclable. In the 21st century, the widespread reliance on fossil fuels has led to environmental pollution, energy depletion, and climate change, posing significant challenges to human society's development and progress. However, renewable energy and new energy are now experiencing rapid growth, poised to become the strategic focus of social development and a key player in the future world energy system. 

For China, one of the essential aspects of future development lies in mastering new energy technologies. However, due to relatively late technological research and certain limitations in the field of new energy generation, China currently faces challenges in achieving stability in the utilization of new energy. Specifically, there are issues with strong intermittency, volatility, and unpredictability in new energy generation. Controlling the power generation of new energy sources presents significant technological difficulties. Moreover, the existing grid capacity remains insufficient to accommodate large-scale integration of new energy generation. These challenges can be summarized as follows:

(1) The impact of volatility and intermittent power generation

In wind power generation, the output power of a wind turbine is directly influenced by the wind speed. Since the energy in the wind is proportional to the cube of the wind speed, the output power of the turbine experiences significant fluctuations due to the inherent instability of natural wind speeds. Artificially controlling wind power is challenging, leading to large variations in turbine output power.

Similarly, in photovoltaic (PV) power generation, the output power of a PV array is linked to the intensity of light, making it highly susceptible to weather conditions and temperature changes. This volatility in solar energy generation parallels that of wind power. Integrating large amounts of wind and solar power into traditional power grids can result in significant current surges, leading to grid frequency deviations, voltage fluctuations, and flickering. For instance, if the voltage at a wind farm drops, wind turbines without low voltage ride-through capability may experience transient faults.

To mitigate these issues, it is crucial for new energy equipment integrated into the grid to possess specified grid-connected technical performance. Additionally, the grid must have sufficient capacity for peak-shaving and power absorption. Active power adjustment and dynamic reactive power adjustment are indispensable features of new energy power generation systems. Furthermore, wind farms and photovoltaic power stations are susceptible to reactive power loss, necessitating the inclusion of reactive power compensation functions in the configuration of new energy power generation systems.

(2) Influence of harmonics

In the new energy power generation system, there are two main ways to bring harmonics to the power grid. Taking a wind power generation system as an example, one is that the power electronic device equipped with the wind power generator itself brings harmonic problems. For a constant-speed wind turbine directly connected to the grid, a certain amount of harmonics is generated by connecting the power electronic device to the grid during the soft start phase. For the variable speed wind turbine, it is connected to the grid system through the rectification and inverter device. If the switching frequency of the power electronic device is just within the range of generating harmonics, it will cause a serious harmonic problem; 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, the wind power system needs to be equipped with a parallel compensation device, but due to the constant changes of harmonics and the complexity of the power grid, under certain conditions, harmonic amplification or even system resonance may occur.

Therefore, in the wind farm, a single variable speed or constant speed wind turbine should be avoided as much as possible. This will cause excessive harmonic voltages locally, and different types of fan hybrid configurations should be used. Secondly, the power system should properly configure the filtering device to reduce the harmonic content in the power grid, and use the dynamic or static reactive power compensation device while suppressing harmonics.

(3) The influence of isolated networks

When the large power grid loses pressure, 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 supply and demand balance state, forming an isolated network operation. At this time, the voltage and frequency in the isolated network are not controlled by the large power grid, and the adjustment support of the large power grid is not obtained. When the load on the load side changes or the output power of the power generation side changes, the supply and demand of the isolated network will be unbalanced, resulting in an isolated network. The voltage and frequency are prone to fluctuations. If the fluctuation range exceeds the allowable safety range, the safety of the equipment will be seriously affected. When the supply is greater than necessary, the voltage and frequency may exceed the allowable range and may cause damage to the user's equipment. When the supply is less than necessary, the inverter will be overloaded and the inverter may be burnt. Therefore, before the new energy is integrated into the power grid, the power dispatch must be strictly checked and audited. For the wind power generation system and the photovoltaic power generation system, the power prediction function is one of the necessary access conditions.

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

The distribution of new energy is broader, but the distribution is not uniform. It is difficult for our country to achieve a relatively unified grid of new energy generation grids. According to the current state of technology development in China, only the technical standards of large-scale grid-connected systems can be unified, but their detection technology is not unified, and there are certain defects in system testing. Therefore, system certification should be further improved.

At this stage, China lacks professional knowledge to analyze the main reasons for the destruction of power system stability and the reduction of power quality in the integration of large and medium-sized new energy sources. Even the factors affecting grid dispatching and affecting grid operation are lack of reasonable identification. Moreover, the problems existing in the grid receiving technology are still being researched and explored. At present, there is no real unified conclusion. It is still difficult to complete the detection of the access system in China. For example, we need to constantly improve the detection of inverters and controllers. In addition, although we are constantly developing and exploring the detection technology of transmission and distribution equipment and two-way metering equipment, compared with the technology of some developed countries in the West, there is still a big gap in China's technology.

Countermeasures to be taken in the future

From the perspective of the impact of new energy grid-connected on power quality of power grids in China, the research and development of China's grid-connected technology in four aspects of DC transmission technology, grid-connected mode, intelligent control technology and scheduling technology are needed. Make greater efforts and enhancements, play a pillar role in renewable energy in the grid-connected mode, and carry out effective operation and control in terms of technology. With the continuous development of more and more widely used information technology and the continuous advancement of technology, artificial control will be replaced by intelligent control one day in the future. In order to effectively improve the technical level of grid system security, it is necessary to use intelligent control technology; in the transmission technology, the research and development of DC transmission technology and large-scale energy storage technology must be continuously strengthened and improved, and then the grid will be operated. The reliability and stability of the system are demonstrated by DC transmission technology, which will reduce the damage to the grid when connected to the grid through large-scale energy storage technology. At the same time, when inter-scheduled work is carried out in areas where new energy is relatively poor or where there is more new energy, the scheduling technology is also widely used at work, and the corresponding technical level will also increase.

Summary: Due to the new energy characteristics and the low level of technology in China at this stage, the new energy grid connection in the current stage has some negative impacts on the power grid application in China, which threatens the safe and stable operation of the power system to a large extent. . (Note: According to the experience of developed countries in Europe, when photovoltaic power generation and wind power generation exceed 6% of the total power grid power, it will affect the stable operation of the power grid, and it is necessary to install energy storage devices.) Therefore, in the face of this situation, Relevant personnel and relevant government departments will improve relevant technologies and standards to ensure that the development of China's power system will be effectively promoted while eliminating the adverse effects of new energy grids on the power grid of China's power grid, and ultimately provide people with security and stability. The power resources ensure the normal production and life needs of people, improve and improve people's quality of life.

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