BESS grid forming: the technological revolution that the Brazilian solar sector needs

With the exponential growth of solar energy in Brazil, we have seen a problem that has become increasingly frequent: the famous “duck curve”, which occurs due to a sharp drop in demand for electricity during times of high solar production, followed by a sharp increase in demand at times when there is no more sunlight from photovoltaic plants. This is the pain of growing, which is accompanied by curtailment – ​​the forced limitation of renewable generation.

The only possible escape is the energy storage. It needs to be done at times when the energy supply is greater than the demand, subsequently inserting this energy into the grid at times when the opposite happens. For this and other reasons, we are observing a growing demand for battery energy storage systems (BESS) in Brazil and around the world.

Not all BESS are created equal: the critical role of PCS

However, one reality that is still unclear to many industry professionals is that not all energy storage systems are created equal. Beyond the obvious differences between battery technologies and storage capacities, there is a fundamental distinction that can determine the success or failure of a project: the type of PCS (Power Conversion System) “inverter” used.

The PCS is the brain of the BESS system, responsible for converting power between direct current (DC) from the batteries and alternating current (AC) from the grid. Most importantly, it defines how the system interacts with the grid and what advanced features are available.

Advanced grid-forming PCS technology has emerged as a key solution to energy transition challenges, offering superior capabilities to traditional grid-following inverters.

Grid Following vs. Grid Forming: Two Philosophies, Different Results

PCS Grid Following: The Conventional Technology

PCS Grid Following operates as a “follower” of the power grid. It synchronizes with the frequency and voltage already established by the grid, adjusting its operation according to the existing parameters. It is a mature and widely used technology, suitable for basic storage applications.

Main Features:

• It depends on the electrical grid to establish voltage and frequency reference;
• It operates in PQ mode (Active and Reactive Power) controlling only the energy flow;
• Cannot form an independent network (microgrid);
• Limited in network stabilization features;
• Automatic Disconnection: They automatically turn off during network failures.

PCS Grid Forming: The New Technological Frontier

PCS Grid Forming represents a paradigmatic evolution. Unlike Grid Following, this technology can form an independent electrical grid, establishing its own voltage and frequency parameters. It operates in both VF (Voltage and Frequency) and PQ (Active and Reactive Power) modes, dynamically adapting to the system’s needs.

Key features:

• Inertia Support: support for insufficient inertia caused by the lack of synchronous generators in power grids with a high proportion of renewable energy;
• Operational Autonomy: Ability to operate independently of the main grid, creating its own voltage and frequency reference;
• Active Voltage Control: Actively regulates system voltage, keeping it within specified parameters even with load variations;
• Active and reactive power control;
• Dynamic Response: Responds quickly to changes in energy demand, automatically adjusting generation to maintain system balance;
• Frequency regulation: Contribute to the overall stability of the network by providing auxiliary services such as frequency regulation, improving system stability;
• Blackstart capability: Can restart systems after total failures;
• Active provision of auxiliary services for network stabilization.

Importance of Black start and VSG

Black-Start and Autonomous Operation is perhaps the most valuable feature for critical applications. This feature enables the BESS to completely boot the grid without external power and autonomously. It can also create a microgrid in a matter of seconds, providing energy autonomy and maintaining critical operations during outages that can last for hours.

PCS Grid Forming actively acts to generate grid stability in weak systems through the VSG (Virtual Synchronous Generator) function. In networks with a low short-circuit ratio (SCR < 3), typical of rural areas or remote connection points, PCS Grid Forming acts as a natural stabilizer, emulating the inertia of conventional synchronous generators, which enables installations in systems that require a maximum level of stability.

Grid forming increases economic gains through stacking benefits

PCS Grid Forming not only helps with energy storage, but also provides valuable services to the electrical system. This enables a stacking of benefits offered to the customer, the main ones being:

• Peak Shaving: Reduces the maximum demand recorded by discharging batteries during consumption peaks;
• Power Backup: Provides immediate power during outages, maintaining critical operations without interruption;
  Energy arbitrage: Recharges batteries at cheaper times (off-peak) and injects into the system at more expensive times (peak), taking advantage of the price differential;
• Frequency regulation: Automatic response to frequency variations in seconds, maintaining network stability;
• Ancillary services: Provides services such as voltage control and virtual inertia;
• Power Quality: Corrects harmonic distortions and fluctuations, protecting industrial equipment;
• Voltage Support: Injects/absorbs reactive power to maintain adequate voltage in weak grids.

Kehua Tech: Global Leadership in PCS Grid-Forming

With over 37 years of consolidated presence in the global market, Kehua Tech has established itself as a leader in PCS grid-forming technologies, both in Brazil and internationally. All Kehua PCS systems have international certifications for grid-forming operation and impress with their technical robustness, withstanding up to 300% overload for 10 seconds – a capacity that demonstrates the engineering excellence of its products.

The company’s credibility in the Brazilian market is proven by its responsibility for the ESS of the largest BESS project in the country, installed at ISA Energia Brasil, with a capacity of 37MW/67MWh. Globally, Kehua has consolidated its leadership position by manufacturing, supplying and monitoring the largest independent grid-forming project in the world: a system with an impressive 300MW/1200MWh installed in Xinjiang, China, which represents a technological milestone in the energy storage industry.

This combination of solid experience, technological innovation and successful cases in world-scale projects positions Kehua Tech as an undisputed reference in the high-performance grid-forming PCS systems segment.

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The opinions and information expressed are the sole responsibility of the author and do not necessarily represent the official position of the author. Canal Solar.