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22

2022

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11

Research on the impact of distributed photovoltaic grid-connected power generation on power grid

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At present, China's power industry is in a stage of rapid development, promoting the development of China's economy, and the scientific and technological content of the power system is also constantly improving, especially photovoltaic power generation technology, fully introducing solar energy, reducing pollution in power operation. As a new type of power generation technology, photovoltaic power generation has environmental protection characteristics, but it is more susceptible to the influence of the surrounding environment. Therefore, it is of great significance to strengthen the research on the influence of distributed photovoltaic power generation on the voltage of distribution network voltage and the solution of voltage limitation.

The impact of distributed photovoltaic power generation on the power grid.

1. The operating characteristics of the distribution network have changed.

With the development of distributed photovoltaic, energy storage and microgrid, the distribution network has gradually developed from passive network to active network, and the operation and maintenance management of the distribution network is more complicated. The local high proportion of distributed photovoltaic access alleviates the trend of grid down, and even leads to changes in the load characteristics of the network in some regions.

2. Increase the difficulty of grid power balance.

Under the existing technical conditions, most areas (counties) do not have distributed photovoltaic power generation monitoring and output prediction means, and traditional load prediction methods cannot calculate the impact of distributed generation, especially in distributed photovoltaic high-proportion access areas, and the impact on load prediction accuracy is more obvious. The grid needs to reserve more spare capacity most of the time to cope with changes in distributed PV output. Distributed photovoltaics, centralized photovoltaics, and wind power generation are superimposed on each other, resulting in difficulties in peak adjustment during the daytime load trough period in local areas, and more prominent holidays.

3. The performance of power grid frequency regulation and voltage regulation is significantly reduced.

First, distributed photovoltaic mostly uses constant power factor (cosφ=1) operation, does not provide reactive power, its concentrated grid-connected area of the lower grid trend becomes lighter, or even reversed, so that the voltage in the local area of the system rises significantly, such as the holiday load trough effect superimposed, the voltage may exceed the limit, serious may lead to photovoltaic power supply off the grid. On the other hand, with the rapid increase of distributed photovoltaic grid-connected capacity, a large number of loads are balanced in situ, and the offset effect on the increase of network supply load is obvious, which is equivalent to replacing some traditional generator sets. However, distributed photovoltaics cannot provide effective reactive power support during the failure, resulting in insufficient dynamic reactive power support, and the transient voltage level gradually decreases, resulting in long-term voltage depression in severe cases. In addition, distributed photovoltaics only provide the power system with active power that changes with the change of optical resources, and cannot adapt to the adaptive adjustment ability of grid frequency fluctuations. In the power generation structure, as the proportion of traditional power supply decreases, the frequency regulation capacity of the system also decreases.

4. Affect the reliability of power supply in the power grid.

On the one hand, when the line fails, distributed PV can supply power to users who have lost power, especially for those very important loads, and the average annual outage time will be greatly reduced. But on the other hand, under distributed PV grid-connected conditions, evaluating the reliability of the distribution network needs to consider new influencing factors, such as the emergence of islands and the randomness of the output power of distributed power sources. Under the current conditions, island operation will affect the safety of maintenance personnel, so it is not allowed, but if the level of operation management can be improved, it can ensure the effective improvement of power supply reliability. In addition, distributed photovoltaics are greatly affected by environmental and meteorological conditions, and the force is also very unstable. Both of these factors affect the improvement of power reliability to a certain extent.