Similarities between distributed photovoltaic power stations and centralized photovoltaic power stations:
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, generally using monocrystalline silicon solar panels or thin-film solar panels. Well-known manufacturers include Yingli and Hanergy Thin Film Power.
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 between distributed photovoltaic power stations and centralized photovoltaic power stations:
1. Different installation locations: Distributed photovoltaic systems are mainly installed on rooftops and agricultural greenhouses, primarily concentrated in densely populated areas of North and South China. Centralized photovoltaic systems are mainly installed in the Gobi Desert and other remote and desolate regions where land is relatively cheap. They are most prevalent in Northwest China, including Ningxia, Gansu, Xinjiang, and Qinghai.
2. Different Grid Connection Voltage Levels: Distributed photovoltaic (PV) systems typically connect to the grid at 380V, usually using low-voltage trip units. The number of grid connection 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 at 35KV. For power plants above 30 MW, a main transformer is usually installed, and the voltage is stepped up to 110KV before grid connection.
3. The secondary equipment used in the power station differs: Distributed photovoltaic power stations use low-voltage 380V grid connection, therefore the primary and secondary equipment used is relatively limited. Inverters are generally wall-mounted inverters, which are simple to install and small in size. Transformers are also small transformers. Commonly used equipment includes power quality monitoring, anti-islanding protection devices, and fault disconnection systems. The requirements for equipment and technical parameters vary depending on the region. However, currently, these are essential devices for every distributed photovoltaic system.
Centralized photovoltaic power plants typically have their own substations due to their higher 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 up to 35kV. The substation contains a lot 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. It is relatively more complex, as the dispatch center directly manages the power plant centrally. The substation also requires power control systems, making it much more complex than distributed photovoltaic systems.
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) power plants. However, currently, grid connection for centralized PV power plants is slightly more difficult and has higher requirements. Distributed PV power plants have 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.
