According to Hefei Power Supply Company, Anhui Grid’s first full direct-current (DC) power supply station demonstration project has been officially put into operation in Hefei. Featuring low carbon, intelligence, safety and high efficiency, the project provides a replicable and promotable demonstration model for the green and low-carbon transformation of urban and rural power consumption during the peak summer power consumption period.

Located at the Changlin Central Power Supply Station of Hefei Power Supply Company in Changlinhe Town, Feidong County, the project features a rooftop photovoltaic power station that steadily outputs direct current. Without AC-DC conversion, electricity is delivered via power routers to supply power for new energy vehicle charging piles, office equipment, air conditioners, lighting and other facilities, marking the official launch of Anhui Grid’s first full DC power supply station demonstration project.

Household daily electricity generally adopts 220V alternating current (AC), while photovoltaic power generates direct current. Traditionally, photovoltaic power must be converted into alternating current through inverters before being connected to conventional electrical equipment. Affected by conversion times and efficiency, approximately 5% to 10% of electric energy is lost during the AC-DC conversion process, directly restricting the utilization efficiency of clean energy.

To solve this problem, the Electric Power Research Institute of State Grid Anhui Electric Power Co., Ltd. and Hefei Power Supply Company jointly carried out the upgrading and renovation of a low-voltage DC power distribution and consumption system at the Changlin Central Power Supply Station as a pilot project. The project integrates multiple energy utilization elements including photovoltaic power generation, wind power generation, energy storage equipment, DC charging piles and building DC loads, building a complete low-voltage DC power distribution and consumption system. After months of construction and commissioning, the demonstration project was officially completed and put into service.

On the power generation side, the project is equipped with a 190-kilowatt rooftop photovoltaic system and a 5-kilowatt wind power device, achieving an average monthly power generation of over 6,000 kilowatt-hours. It is supported by a 60-kilowatt/120-kilowatt-hour energy storage power station and low-voltage flexible interconnected power router. On the power consumption side, the building’s living facilities have completed DC adaptability renovation. The station is equipped with 8 charging guns with a total power of 320 kilowatts, meeting the power demand for office use and official vehicle charging. Two low-voltage DC voltage levels of 750V and 220V are set to cover diverse power consumption scenarios in the station.

The low-voltage flexible interconnected power router serves as an intelligent dispatcher for DC power. After the project was launched, the direct current generated by on-site photovoltaic and wind power systems is precisely allocated via the power router, directly supplying power to DC loads such as buildings and charging piles. Excess electric energy is stored in the energy storage system. During nighttime with no photovoltaic power generation, the energy storage system discharges electricity to realize self-sufficient power circulation within the station. This mode reduces the comprehensive electric energy loss to 2%–3%, improves the comprehensive system operational efficiency by 7% compared with the traditional AC power supply mode, and greatly boosts the utilization rate of clean energy.

“The full DC power supply mode completely eliminates repeated AC-DC conversion links, achieving remarkable energy conservation and efficiency improvement results,” said a relevant staff member of Hefei Power Supply Company. Overall, the project boasts five core advantages: low carbon, intelligence, safety, reliability and high efficiency.

Relying on flexible control technology, the system can dynamically adjust electric power flow and load distribution, enabling full visibility, accurate measurement, flexible regulation and precise control of power generation, grid operation, energy storage and power consumption links. The project builds an AC-DC interconnected and mutually supportive power supply grid, improving the power supply reliability of the distribution network and reducing electric energy loss caused by repeated AC-DC conversion and line power transmission. The operation of this project provides a replicable and promotable demonstration model for the green and low-carbon transformation of urban and rural power supply and the large-scale application of low-voltage DC distribution networks.

Source: Hefei Evening News

Translated by Shao Hanzhe, intern