Distributed photovoltaic (PV) systems are typically built on rooftops, factory roofs, and vegetable greenhouses, making full use of space. So what are the differences between centralized and distributed PV systems?
Difference between centralized photovoltaic systems and distributed photovoltaic systems
Similarities
1. The principle is the same: both utilize solar energy to convert it into electrical energy, and then transmit the generated electricity to the power grid for production and daily life.
2. The components are the same, and they are generally monocrystalline silicon solar panels or solar thin films.
3. The primary equipment used is basically the same, including inverters, transformers, combiner boxes, etc. The inverter converts the generated direct current into alternating current; the transformer steps up the alternating current converted by the inverter; the combiner box collects the direct current from the solar panels and sends it to the inverter.
Differences
1. Different installation locations:
Distributed photovoltaic (PV) systems are mainly installed on rooftops and agricultural greenhouses, primarily concentrated in populated areas of North and South China. Centralized PV systems are mainly installed in the Gobi Desert and other remote, desolate regions where land is relatively cheap. They are predominantly located in Northwest China, including Ningxia, Gansu, Xinjiang, and Qinghai.
2. Different grid connection voltage levels:
For distributed photovoltaic (PV) systems, grid connection is typically 380V, usually achieved using low-voltage trip units. The number of grid-connected points in a distributed system depends on the specific circumstances, ranging from one to several. Centralized PV power plants, on the other hand, commonly connect to the grid at 35kV or 110kV. If the power plant is 30 MW or less, a main transformer is generally not installed, and it typically connects to the 35kV grid. For power plants exceeding 30 MW, a main transformer is usually installed, which steps up the voltage to 110kV before grid connection.
3. The secondary equipment used in the power plants is different:
Distributed photovoltaic power stations use low-voltage 380V grid connection, so the primary and secondary equipment used is relatively limited. The inverters are typically wall-mounted inverters, which are simple to install and small in size. The transformers are also small-sized transformers.
Centralized photovoltaic power plants typically have their own substations due to their high voltage levels. Inverters are usually located in the substation building and are quite large. The voltage boosting function is performed by a prefabricated transformer, typically raising the voltage to 35kV. The substation contains a considerable amount of equipment, including primary equipment such as station service transformers, switchgear, various instrument transformers, arc suppression coils, and main transformers. Secondary equipment includes microprocessor-based protection systems, electricity meters, and dispatch data panels. The system is relatively complex, as the dispatch center provides centralized management of the power plant.
4. Different transmission distances: Distributed photovoltaic power generation is generally connected to the grid locally, with very low or even zero line losses. It supplements the local electricity supply for local and nearby users. Centralized photovoltaic power stations, on the other hand, transmit electricity through high-voltage grids, layer by layer to higher voltage levels, and then to regions like East China to achieve the West-to-East Power Transmission Project.
In summary, there are many similarities and differences between distributed and centralized photovoltaic (PV) systems. However, currently, national policies support distributed PV power generation, while grid connection for large-scale centralized PV systems is slightly more difficult and has higher requirements. Distributed PV has a better future, and the investment amount for power plants of similar size is roughly the same. Moreover, distributed PV systems are installed in areas with high population density, making maintenance more convenient.
