Does poor grid power quality have an impact on photovoltaic power generation systems?

Power quality mainly consists of two indicators: voltage and frequency. General deviations (e.g. 5%) in these two indicators will not affect the stability of the power system. When there was a power shortage in the 1970s, the frequency of the East China power grid was as low as 46 Hz/S, and low voltage was common, but the system still managed to survive. Therefore, power quality has little to do with system stability.

Will photovoltaic grid-connected power generation systems affect power quality?

Technically, the difficulty in grid connection is due to power quality. Grid companies have high requirements for the relative stability of power supply, while photovoltaic power generation is less predictable and less reliable due to weather changes. I personally suggest that you consider installing large-capacity energy storage devices, such as battery packs, to alleviate the situation of severe load reduction to a certain extent when the weather changes greatly.

What impact does distributed photovoltaic power generation have on the power grid?

Due to the unstable output of distributed photovoltaic power generation, after connecting to the public power grid, the public power grid is needed as a backup. With the large-scale connection of distributed photovoltaic power generation to the power grid, it will have a certain impact on the stability and security of the power grid. What impact will it have on the power grid?

(1) Impact on power grid planning. Load forecasting is the basis of grid planning and design, and whether the load can be accurately predicted is a prerequisite for grid planning. The grid connection of distributed photovoltaic power generation has increased the difficulty of load forecasting in the area where it is located and changed the existing load growth pattern. The access of a large number of distributed power sources has made the transformation and management of the distribution network more complicated.

(2) Different grid connection methods have different impacts.

① Distributed photovoltaic power generation has no impact on the grid when it is off-grid;

② Distributed photovoltaic power generation that is grid-connected but does not transmit power to the grid will cause voltage fluctuations;

③ The grid connection method that is grid-connected and transmits power to the grid will cause voltage fluctuations and affect the configuration of relay protection.

(3) Impact on power quality. The important impact of distributed photovoltaic power generation access is that it causes changes in the voltage distribution on the feeder, and the magnitude of the impact is closely related to the access capacity and access location. Photovoltaic power generation is generally connected to the grid through an inverter. The frequent opening and closing of such power electronic devices is prone to harmonic pollution.

(4) Impact on relay protection. Most of my country's distribution networks are single-power radial structures, and most of them adopt quick-break and time-limited quick-break protection forms, which are not directional. This protection method can effectively protect all lines in the existing radial distribution network. However, after the distributed power source is connected to the distribution network, its injected power will reduce the relay protection range and cannot reliably protect the entire line. It may even cause the relay protection of the distributed photovoltaic power generation to malfunction when other parallel branches fail.