**I. Introduction**
With the release of the State Council document No. 24 in 2013, China has entered a critical phase in the development of distributed photovoltaic power plants. Given the unique technical and application characteristics of photovoltaic (PV) energy, this paper emphasizes that for the sustainable and healthy growth of distributed PV systems, it is essential to integrate smart micro-grid technologies. This approach combines PV power with other renewable sources, energy storage, and advanced control systems to create a smart photovoltaic micro-grid. Such a system ensures efficient utilization of solar energy, mitigates the inherent instability of PV generation, enhances grid reliability, and accelerates the widespread adoption of clean energy solutions.
**II. Characteristics of Photovoltaic Power Generation**
Photovoltaic power generation offers several advantages, including its cleanliness, abundance, and lack of geographical constraints, along with low maintenance costs. Compared to other renewables like wind, nuclear, or biomass, PV has clear competitive benefits. However, despite these strengths, PV also faces significant challenges. Historically, high costs were the main barrier to large-scale deployment. Since 2006, however, the cost of PV installation has dropped dramatically—from 60 yuan per watt to around 8 yuan today—driving a rapid increase in global PV capacity.
Yet, as PV penetration grows, new technical limitations have emerged. First, the instability of PV output is due to the variability of sunlight. At night, no electricity is generated, and sudden cloud cover can cause sharp fluctuations in power output. These variations pose challenges for grid stability, especially when PV capacity exceeds 15% of the grid’s total capacity, risking grid failure.
Second, PV has a low energy density, requiring large land areas for significant power generation. This makes large-scale ground-mounted PV projects unsuitable for densely populated regions like eastern China. Hence, the push for distributed PV systems, such as rooftop installations, which align better with local load patterns.
Third, PV lacks flexibility in adjusting output to match demand. When demand rises, PV cannot supply more power; when demand falls, it cannot reduce output accordingly. To address this, grids must either rely on backup power sources or use energy storage systems to balance excess generation.
As PV scales up, these issues become more pronounced. To ensure long-term viability and broader adoption, innovative solutions are needed to overcome these limitations.
**III. Smart Photovoltaic Microgrids: A Viable Solution**
Smart photovoltaic microgrids represent a promising solution to these challenges. A microgrid is a localized power network that integrates multiple distributed energy sources, loads, storage systems, and control devices. It can operate independently or connect to the main grid, offering greater resilience and flexibility.
A smart photovoltaic microgrid uses PV as the primary energy source, supplemented by other renewables such as wind, small hydro, biomass, and microturbines. Energy storage systems help stabilize supply, while intelligent control ensures efficient power management. The guiding principle is “PV-based, multi-energy complementary, generation-storage combination, and intelligent regulation.â€
Key features include:
1. **Integration of Multiple Renewable Sources**: Combining PV with wind, hydro, and biomass helps smooth out power fluctuations and improve reliability.
2. **Energy Storage Technology**: Advanced storage solutions like vanadium flow batteries, flywheels, and supercapacitors provide backup power during outages and manage peak demand.
3. **Power Quality Control and Protection Systems**: These ensure stable voltage, frequency, and power factor, while protecting against faults and harmonics.
4. **Intelligent Information Systems**: Real-time data exchange between the microgrid and the main grid enables efficient scheduling and coordination, enhancing overall grid stability.
**IV. Construction of Smart Photovoltaic Microgrids**
Building a smart photovoltaic microgrid involves careful planning, equipment selection, and integration. It starts with assessing local energy needs, followed by designing power generation, storage, and distribution systems based on available resources and load profiles. Key components include PV arrays, wind turbines, microturbines, battery systems, and a central control unit.
The microgrid must be connected to the main grid through isolation transformers and protection devices, allowing it to switch between grid-connected and islanded modes. Communication with the main grid’s dispatch system is crucial for real-time monitoring and control.
Maintenance of a microgrid is more complex than traditional grids, requiring skilled personnel to manage PV panels, storage systems, and control units. Regular testing and remote monitoring are essential to ensure reliable operation.
**V. Conclusion**
The development of smart photovoltaic microgrids offers a sustainable path for integrating renewable energy into the power system. By addressing the limitations of PV generation and enhancing grid stability, these systems promote the efficient use of clean energy and reduce reliance on fossil fuels. As microgrids expand, they will play a key role in transforming buildings and infrastructure into power-generating assets, supporting urbanization, rural development, and the broader goals of the third industrial revolution.
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