Quzhou, Zhejiang: Three-level synergy solves photovoltaic volatility challenges

As distributed photovoltaic (PV) systems are connected to the grid at scale in mountainous areas, power quality in distribution networks is facing increasingly severe challenges. During the midday period when PV generation peaks, voltage tends to exceed limits; in the evening when electricity demand surges, PV output drops sharply, often leaving an insufficient level of distribution network voltage — this paradox was once a serious issue in terms of power supply in Quzhou's mountainous regions. It has changed with the implementation of a series of voltage regulation measures implemented by State Grid Quzhou Power Supply Co (State Grid Quzhou).

Construction workers carry out voltage regulation equipment installation for the power grid along a mountain road in Jiangshan, Quzhou. [Photo provided to chinadaily.com.cn]

In pilot areas such as Hecun village, Xiakou town, and Qingyang village in Jiangshan city, distribution lines have been equipped with line voltage regulators, on-load tap-changing transformers, and low-voltage Unified Power Quality Conditioner (UPQC) devices. They do not operate independently, but rather form a three-level coordinated regulation chain extending from medium-voltage lines to distribution substations, and then to low-voltage lines, akin to installing an intelligent voltage stabilization system for the power grid.

The core capability of this system lies in automatic matching. When midday PV generation surges and voltage climbs, the voltage regulation equipment automatically steps down the voltage; when the evening load surges and voltage drops, the system promptly boosts the voltage. The entire process requires no manual intervention, and offers rapid and precise response, effectively suppressing the severe voltage fluctuations caused by PV variability.

"In the past, during peak PV generation periods or evening peak hours, household appliances in some farmers' homes and equipment at nearby processing plants were easily affected," explained an official from State Grid Quzhou. "Now, through three-level coordinated regulation, voltage qualification rates and power supply reliability in the pilot areas have seen tangible improvements."

Data show that after systematic treatment, voltage quality in Jiangshan city's pilot townships has improved significantly compared to the same period last year, with voltage limit violations and low-voltage incidents on the user side substantially reduced. These results have also brought tangible changes to local residents and businesses — home appliances run more stably, and production line electricity use is more reliable.

As a critical component of the voltage governance in Zhejiang's mountainous new-type power system demonstration project, the implementation of this solution not only provides a technical benchmark for the high-quality development of the local distribution network in Quzhou, but also explores a replicable and scalable path for voltage governance in mountainous areas with high PV penetration rates across the province and even nationwide.

State Grid Quzhou will continue to expand the coverage of governance measures, deepen intelligent regulation methods, and enhance the distribution network's capacity to accommodate new energy and the quality of power supply services.