Fanghe substation now fully equipped

On Aug 27, State Grid Shaanxi Power Supply finished the major equipment installation for a 35-kilovolt static power generator at Fanghe substation in Ansai district, Yan'an, Shaanxi province.

The 330-kV Fanghe substation is one of the main centers for collecting and transmitting renewable energy from northern Shaanxi to other regions. It is connected to 14 renewable energy stations, with a total installed renewable capacity of 1.12 million kilowatts.

It is also adjacent to the ±800-kV Qingdong ultrahigh-voltage direct current converter station, and sits at a key point of the Shaanxi-Anhui and Shaanxi-Henan UHVDC projects, serving in the national energy strategies of "West-to-East Power Transmission" and "North-to-South Power Supply".

With the large-scale grid integration of new energy, long-chain grid connection has led to issues such as low short-circuit ratios at grid connection points and weak voltage support.

Additionally, UHVDC blocking faults can easily induce transient overvoltage at the terminals of new energy generation units, causing unit disconnection from the grid.

These problems have become common industry bottlenecks that constrain the efficient integration of new energy and the secure, stable operation of power grids.

To address this bottleneck, State Grid Yan'an Power Supply, in collaboration with the China Electric Power Research Institute, has launched the world's first static power generator demonstration project, or SPG project, in the Fanghe substation.

"The high-voltage, large-capacity insulated gate bipolar transistor series valve is the 'heart' of the SPG project. We have conducted research on this for 16 years to break down foreign technological barriers," said Qiao Guangyao, executive director of the SPG project of the China Electric Power Research Institute.

It's the world's first 35 kV, 30 megavar SPG and its core equipment is independently developed and domestically produced, Qiao said.

The equipment adopts a two-stage alternating current and direct current topology.

The AC side utilizes IGBT series valves tailored to grid operation requirements, while the DC side employs isolated DC-DC converters to integrate a supercapacitor and achieve voltage stabilization and disturbance rejection.

Leveraging vector reshaping control technology and high-current overload converter valves, the system delivers three core advantages: robustness, precise control, and reliable support. It can operate across all grid conditions, including fault, recovery, and steady-state modes, with a millisecond-level response to grid disturbances, providing support for the power grid's secure operations.

"Participating in this project is a great honor to me, and it brought me a deep sense of responsibility," said Li Yue, deputy team director of the company's substation maintenance center. He added that he felt proud of witnessing such a technological breakthrough in domestically produced power equipment.

The project has been added into the second batch of original technology innovation demonstration projects of State Grid Corporation of China.

Once in operation, it is expected to increase the new energy power transmission capacity of the Fanghe substation by 138 megawatts and add 200 million kilowatt-hours of new energy electricity fed into the grid annually — equivalent to the annual electricity consumption of 66,000 households.

It can also save approximately 60,000 metric tons of standard coal every year and reduce carbon dioxide emissions by about 156,000 tons, offering a replicable "Yan'an model" to achieve self-sufficiency in key equipment of China's new-type power system.

Old city renovation

Zichang, a county-level city in Yan'an, is famous for having many revolutionary sites. The most important of them is the site of the Wayaobu Conference, an enlarged meeting of the Political Bureau of the Central Committee of the Communist Party of China held on Dec 17, 1935 at Wayaobu, Zichang.

In the past, the old city of Zichang featured narrow streets and alleys, dense buildings and outdated power distribution lines. These conditions led to low voltages and frequent power outages, which not only affected residents' life quality but also hindered the development of Red tourism and urban renewal.

In 2023, Zichang city launched the old city renovation project.

"As workers in the power sector, we face no fear in confronting tough challenges, remain true to our original aspirations, and safeguard the light for countless households through our steadfast commitment and responsibility," said Liu Xin, deputy general manager of State Grid Zichang Power Supply.

The power grid upgrade project covers three streets and two 10-kV lines measuring up to 8.4 kilometers. A total of 17 box-type transformers and seven ring main units have been installed, and 58.4 km of high-and low-voltage cables have been laid, benefiting 4,751 households and businesses.

In alignment with the overall urban renewal strategy, the company has adopted an integrated operational model. It partnered with the providers of water, heating, gas, and communications to coordinate plans and carried out excavations together.

During construction, workers from the company prioritized operations in the early morning, which is the off-peak time for electricity usage, and adopted emergency equipment such as mobile power supply vehicles and portable power stations in critical areas to ensure uninterrupted power supply throughout the process.

This approach minimized the area and duration of power outages, reducing their effect on residents' daily lives.

Focusing on the Wayaobu Conference site and other revolutionary sites, the company buried main cables underground, renovated the looped network power supply and installed three levels of residual current protection devices.

It has also established a specialized guarantee mechanism for major events, which includes advance inspections and on-site monitoring, to ensure safe, and stable power supply for these revolutionary sites.

After the project is completed, the area's power supply reliability rose from 99.89 percent to 99.98 percent. Meanwhile, the average power capacity per household increased from 1.67 kilovolt-amperes to 3.4 kVA, benefiting 4,751 households and businesses.

"The voltage has become very stable thanks to the renovation project. The electrical equipment in my store now operates smoothly, and we barely have any power trips or outages," said Gao Wangping, a shop owner on the city's Nanmen Old Street.

"The power supply company followed the overall urban renovation plan, implemented construction during off-peak periods, and ensured the stable power supply after the renovation project, benefiting local residents and businesses," said Qin Xinxin, Party secretary of Linhushan residential area of Wayaobao subdistrict in the city.

In the old city of Zichang today, all overhead cables have disappeared underground, and the streets have a fresh new look. The stable and reliable power supply has enhanced residents' sense of happiness and injected vitality into the development of commerce and Red tourism.