Revealing the Differences and Advantages between High-Voltage Grid Connection and Low-Voltage Grid Connection
In the process of construction and operation of photovoltaic power stations, choosing an appropriate grid connection method is crucial. High-voltage grid connection and low-voltage grid connection are two commonly used grid connection technologies, and each has its unique advantages and limitations. Next, we will explain in detail the differences between these two grid connection methods.
High-voltage grid connection usually refers to directly connecting a photovoltaic power station to a medium-high voltage power grid. Its voltage level is generally above 10 kilovolts. Common voltage levels include 10 kV, 35 kV, etc. The high-voltage grid connection system can carry a larger power transmission capacity and is suitable for large-scale ground power stations, large industrial and commercial parks and other scenarios.
Due to the high voltage level of the high-voltage grid connection system, a series of high-voltage equipment is required, including high-voltage switchgear, transformers, protection devices, high-voltage cables, etc. In addition, high-voltage grid-connected inverters, monitoring systems, high-voltage metering equipment, grounding systems and auxiliary equipment are also essential. The combined effect of these devices enables the high-voltage grid connection system to efficiently send the electric energy generated by the photovoltaic power station to the large power grid. The high-voltage grid-connected inverter has a high-voltage output capacity. The AC grid-connected voltage levels of 1100V DC high-voltage inverters are generally 480Vac, 500Vac, 540Vac, etc., and the AC grid-connected voltage level of 1500V DC high-voltage inverters is 800Vac.
Typical 480Vac high voltage grid-connected system diagram
Typical 800Vac high voltage grid-connected system diagram
The voltage level of the low-voltage grid connection system accessing the power grid is usually 380V (three-phase) or 220V (single-phase), which is exactly the common voltage in our daily electricity consumption. After being converted into alternating current by an inverter, it is directly connected to the low-voltage distribution network to supply power for users. Therefore, the low-voltage grid connection system is more suitable for smaller-scale or distributed photovoltaic systems with a higher proportion of self-consumption. Such systems are commonly found on residential roofs and in small industrial park buildings.
The low-voltage grid connection system is relatively simple. The main equipment includes low-voltage switchgear and distribution boxes, grid-connected inverters, electric energy metering equipment, etc. The low-voltage grid connection system does not require complex power transmission equipment, and installation and maintenance are also more convenient. For residents and small industrial and commercial users, the low-voltage grid connection system is undoubtedly a more economical and practical choice.
Typical 380Vac low voltage grid-connected system diagram
Typical 220Vac low voltage grid-connected system diagram
When deciding whether a photovoltaic power station adopts high-voltage grid connection or low-voltage grid connection, multiple factors such as project requirements, investment budget and grid conditions must be comprehensively considered. The high-voltage grid connection mode is more suitable for large-scale ground photovoltaic power stations that require long-distance transmission, while the low-voltage grid connection is more suitable for small-scale, short-distance transmission distributed projects. No matter which grid connection method is finally chosen, ensuring the efficient, stable and economical operation of the system is always crucial.