Smart String Grid-Forming ESS: A New Era of Grid-Forming ESS

As global efforts to achieve an energy transition ramp up, the proportion of electricity generated from renewable energy is rapidly increasing. Today, the penetration rates of renewables in both China and Europe exceed 30%. This calls for the construction of new power systems so that more renewable energy can be consumed, and more power electronics equipment can be used.

It is worth noting that the intermittent and unpredictable nature of renewable energy poses challenges for large-scale grid integration, which impacts the stability of power grids across many countries. Unlike traditional generators, renewable systems cannot provide frequency and voltage support. Furthermore, as renewable electricity feeds into power grids, these grids face the increased risk of random fluctuations, inadequate frequency and voltage regulation, and oscillation.

With the rapid growth of renewable energy, grid stability and renewables integration (grid balance) have emerged as critical challenges. A grid-forming energy storage system (ESS) offers capabilities such as reactive power compensation, wideband oscillation damping, inertia response, frequency regulation, and peak shaving. These functions enhance energy-capacity balance and grid stability, establishing grid-forming technology a key trend.

However, the wide commercial use of grid-forming ESS still faces four major global technical challenges:

1. Instability of parallel systems: Multiple voltage source devices operating in parallel within a plant face challenges regarding the coordination of voltage amplitude and phase, resulting in significant circulating current issues. Grid-forming ESS must therefore address transient fluctuations in grid impedance, voltage, phase angle, and frequency, presenting substantial stability challenges.
2. Wideband oscillation damping: The oscillation frequency range caused by power electronic devices is broad, and the oscillation issues involve a great number of control loops with increased complexity.
3. Strong overload support: Similar to synchronous generators, grid-forming ESS must provide the transient overload capability. When in the short-circuit transient state, the overload current surges, and the component loss increases exponentially. As a result, the component junction temperature exceeds safe parameters, causing component failure and equipment damage.
4. High safety and reliability: When transient overvoltage occurs on the power grid, the power grid current is back-fed to the ESS. Therefore, grid-forming ESS must offer higher reliability.

2. Technical Breakthrough: Smart String Grid-Forming ESS

Calling upon its expertise in the PV and ESS fields, especially regarding grid friendliness and grid-forming technologies, Huawei Digital Power proposes the Smart String Grid-Forming ESS technology system and defines the core standards of grid-forming capabilities: Grid-forming ESS should have grid-forming capabilities for all performances, all grid conditions, and the full lifecycle of power generation, transmission, distribution, and consumption.

Huawei FusionSolar offers six primary capabilities for utility-scale grid-forming ESSs, serving as the key technological foundation of the new power system. These include:

1. Short circuit level: 1x to 6x short-circuit current, response within 10 ms
2. Inertia: inertia time constant ranging from 0s to 20s, action within 5 ms
3. Primary frequency regulation: plant-wide response time < 200 ms
4. Power oscillation damping: 0.1 Hz to 100 Hz wideband oscillation damping
5. Black start: black start for a GWh-level plant within 10 minutes
6. On/Off-grid switching: Seamless switching between on-grid and off-grid modes

Leveraging these six capabilities, Huawei’s Smart String Grid-Forming ESS can ensure 24/7 stable grid forming regardless of the SOC, grid SCR, and future evolution of the energy architecture. It offers reliable support for the power system and applies to various business models.

On the generation side, the solution can be adapted to any grid and power can be stably transmitted. The voltage, frequency, and power angle control functions and application effects are equivalent to those of synchronous condensers. The grid-forming ESS solution features simple maintenance and lower lifecycle investment.

On the transmission and distribution side, the solution stabilizes voltage and frequency, supports black start, and mitigates weak power supply in load centers. The electric power market is expanding from energy and capacity markets to ancillary service markets such as reactive power and inertia services. Huawei’s Smart String Grid-Forming ESS features One-Fits-All, meaning one platform that is adaptable to diverse business models and supports flexible evolution.

On the consumption side, seamless on/off-grid switching and stable off-grid operation enable microgrids that are 100% powered by renewables.

Huawei Digital Power is committed to promoting high-quality industry development and developing future-oriented grid-forming ESS technologies with stricter standards. With the construction of new power systems accelerating, we believe that future-proof grid-forming ESS products should both satisfy existing demands and accommodate future evolutions. Some regions currently require minimal or no grid-forming capabilities, but demand will surge with increased renewables grid integration. Our system should be designed to evolve, ensuring it meets customer needs at every stage through software and hardware upgrades.

3. Implementation: Successful Applications in Complex Scenarios

• Grid-forming ESS plant in Ngari prefecture

In Ngari prefecture, Southwest China, there is a 30 MW PV plant situated at an altitude of 4600 m, where temperatures drop to –20°C and the local power grid is weak. Under such extreme conditions, the actual output power of this plant was previously only 1.5 MW. However, after the configuration of the 6 MW/24 MWh Smart String Grid-Forming ESS, the plant switched from grid-following mode to grid-forming mode on November 11, 2024. When the plant runs in grid-forming mode at full capacity (6 MW), the PV output increases from 1.5 MW to 12 MW, feeding 75% more PV energy to the power grid. According to the plant’s statistics of the power plant, the ESS provides grid support more than 40 times within 10 days. The successful completion and operation of this project marked a breakthrough in renewables grid-forming technology in plateau environments, providing stable and reliable clean energy for local and surrounding areas, effectively promoting local economic and social development, and improving residents’ quality of life.

• Microgrid energy storage project in The Red Sea destination, Saudi Arabia

The 400 MW PV and 1.3 GWh ESS project deployed near the Red Sea coast in Saudi Arabia is the world’s first GWh-level grid-forming project, spanning 100 km. The project uses Huawei’s Smart PV+ESS Solution and has been fully operational since September 2023. It has provided over 1 billion kWh of green electricity to urban loads including airports, hotels, desalination plants, sewage treatment plants, and chiller plants, becoming the world’s first city microgrid entirely powered by renewable energy. Huawei’s Smart String Grid-Forming ESS features large-scale grid-forming technology, microgrid fault ride-through capability, self-synchronous black start across 100 km in minutes, and proactive cell-to-grid safety, guaranteeing reliable power supply in the local area.