Distributed photovoltaic power generation has the following characteristics:
First, the output power is relatively small. Generally speaking, the capacity of a distributed photovoltaic power generation project is within a few kilowatts. Unlike centralized power plants, the size of a photovoltaic power plant has little impact on power generation efficiency, and therefore little impact on its economics. The return on investment for small photovoltaic systems is not lower than that for large ones.
Secondly, it produces minimal pollution and offers significant environmental benefits. Distributed photovoltaic power generation projects generate electricity without noise or pollution to the air or water.
Third, it can alleviate local power shortages to some extent. However, distributed photovoltaic power generation has a relatively low energy density, with a power output of only about 100 watts per square meter. In addition, the roof area suitable for installing photovoltaic modules is limited, so it cannot fundamentally solve the power shortage problem.
Fourth, it allows for both power generation and consumption. Large-scale ground-mounted power plants generate electricity by stepping up the voltage and connecting to the transmission grid, operating solely as power generation plants; while distributed photovoltaic power generation connects to the distribution grid, allowing for both power generation and consumption, and requiring local consumption as much as possible.
Distributed photovoltaic power generation has the following impacts:
1. Impact on power grid planning. The grid connection of distributed photovoltaic power increases the difficulty of load forecasting in the areas where they are located and changes the existing load growth pattern. The integration of a large number of distributed power sources makes the transformation and management of the distribution network more complex.
2. Different grid connection methods have different impacts. Off-grid distributed photovoltaic (PV) systems have no impact on the power grid; grid-connected distributed PV systems that do not transmit power to the grid will cause voltage fluctuations; grid-connected systems that transmit power to the grid will cause voltage fluctuations and affect the configuration of relay protection.
3. Impact on power quality. A significant impact of distributed photovoltaic (PV) grid connection is the alteration of voltage distribution on feeders. The magnitude of this impact is closely related to the grid connection capacity and location. PV power generation is typically connected to the grid via inverters. The frequent switching on and off of these power electronic devices can easily generate harmonic pollution.
4. Impact on relay protection. China's distribution networks are mostly single-source radial structures, employing instantaneous and time-limited instantaneous protection methods, which lack directionality. When distributed generation is integrated into the distribution network, the injected power reduces the relay protection range, making it unreliable for protecting the entire line. Furthermore, faults in other parallel branches may cause malfunctions in the relay protection systems of distributed photovoltaic systems.
