What impact does distributed PV have on the grid?

The dynamics of distribution networks are undergoing significant transformations, influenced by the integration of distributed photovoltaic (PV) energy systems. As distributed PV, along with energy storage and microgrid technologies, continues to advance, distribution networks are transitioning from their traditional passive roles to more active ones. This shift has introduced a new layer of complexity to the management and operational maintenance of these networks.

The challenge of maintaining grid power balance has escalated. Presently, in many areas, there lacks adequate monitoring and predictive forecasting for distributed PV generation. This gap renders traditional load forecasting methods ineffective, particularly in locales with substantial distributed PV integration, thus impairing the precision of load predictions. Consequently, grids are compelled to maintain higher levels of reserve capacity to accommodate the variability in distributed PV generation. The combined impact of distributed PV, centralized PV, and wind generation complicates peak load management, especially during low-demand periods and holidays.

Grid stability, in terms of frequency and voltage regulation, has been adversely affected. Distributed PV systems, operating with a constant power factor (usually cos φ = 1), do not contribute to reactive power. This situation has led to a diminishing or even reversal of the off-grid trend in areas with centralized grid connections, causing significant voltage increases in parts of the system. Voltage levels may surge beyond acceptable limits during peak load times or holidays, potentially resulting in the disconnection of PV systems in extreme scenarios.

The swift expansion of distributed PV connections has facilitated local load balancing, effectively counteracting the rise in grid supply load and substituting some traditional power generation units. However, during faults, distributed PV's inability to supply reactive power leads to inadequate dynamic reactive power support, causing a drop in transient voltage levels and, in extreme cases, prolonged voltage dips.

Distributed PV systems supply active power based on sunlight availability but cannot adjust to grid frequency fluctuations adaptively. As the share of conventional power sources decreases, the grid's frequency regulation capacity diminishes.

Furthermore, the reliability of power supply faces new challenges. In the event of a line fault, distributed PV can provide power to disconnected customers, notably reducing the average annual outage time for critical loads. However, assessing the reliability of the distribution network under grid-connected distributed PV conditions requires consideration of new factors, such as the potential for islanding and the unpredictable nature of distributed generation output.

In summary, the rise of distributed PV power generation is reshaping the operational landscape of distribution networks, making them more active but also complicating their operation and maintenance. This evolution poses challenges in power balancing, grid stability, and reliability, necessitating innovative solutions and adjustments in grid management practices.