The Evolving Landscape of BESS Control Systems

The Battery Energy Storage System (BESS) industry is relatively young and has undergone major changes until it became what it is today. As BESS technology advances, so do the control systems that ensure optimal performance. A BESS system is more than just batteries; it's a complex system of equipment items such as PCS, MV switches, transformers, sensors, measuring devices, and, more which all have their control elements.

While batteries represent a significant cost factor (70-80%), the control system is the heart of the BESS operation, creating synergy between the installed equipment, ensuring safety and optimal use, and calculating the profitability time for system activation. The control system presents site information on unique dashboard pages for analysis. Integrators at BLEnergy assess and characterize customer needs, plan and select appropriate suitable equipment, and create an efficient control system to conduct the BESS.

From Siloed Systems to Collaborative Layers

Initially, developers depended on battery manufacturers or PCS manufacturers for the control systems. The problem with OEMs providing the entire system is that they often prioritize equipment protection over maximizing client needs.  As the industry developed, with more regulation requirements, safety aspects, revenue layers, enhanced functionalities, local requirements, and cybersecurity, the limitations of these single systems became apparent. The modern approach embraces a multi-layered control system, with each layer dedicated to its specific function The BESS integrator separates the responsibility of site controlling systems and allows the software developer to focus on improving and maximizing the BESS equipment.

In the past, a single control system covered the entire system, from controlling the cell up to the grid integration, known as EMS (Energy Management System). Today, we are observing a shift towards four definitive layers, though some overlap remains, marking a clearer delineation than previously seen.

Key Layers in Battery Storage Management

1.  BMS – Battery Management System monitors battery cells and enclosure equipment in real-time, ensuring cell safety, managing voltage range, and enforcing current limitations. The collected information is transferred to the above layer, while also capable of autonomously responding to emergencies.

2.  ESMS – Energy Storage Management System controls all BESS components, including batteries, PCSs, transformer sensors, and MV switchgear. It's flexible, modular, and tailored to site and equipment needs, ensuring optimal performance. Safety is prioritized with comprehensive monitoring, managing BESS startup activation, and safe mode transitions. The ESMS consolidates all BESS data into one dashboard for analysis and oversight.

3.  SCADA - Supervisory Control and Data Acquisition oversees site-wide control and cybersecurity, receiving data from all systems (generator, PV system, energy storage system, consumers) to manage and improve energy use. It provides a unified dashboard displaying all site components for easy monitoring. SCADA also ensures compliance with local cybersecurity regulations, safeguarding site operations.

4.  Optimizer - This layer serves as the last interface with the grid operator before connecting to the grid. It can link directly to the BESS system as a standalone unit or to a microgrid that includes the BESS. This software layer can optimize multiple sites for the same client working under the same grid operator or as part of a virtual power provider. It utilizes advanced algorithms, often incorporating machine learning and AI, to maximize the efficiency of the BESS. Predicting the optimal charge and discharge cycles ensures compliance with regulatory boundaries while maximizing revenue streams.

Benefits of a Multi-Layered Approach

The primary challenge for clients is to ensure comprehensive layer coverage in the design, avoiding both overlap and gaps. Addressing this ensures an efficient and prompt commissioning phase. On the other hand, overlooking this upfront may lead to substantial delays and change orders from suppliers during the project's final stages on-site.

Adapting the EMS in projects has significantly accelerated grid connections. In our first project using the system, the Holit project—a 2.5 MW, 10 MWh, built for Doral —we were able to expedite commissioning, reducing it to just a few weeks. Since then, we’ve consistently observed improvements across various projects.

As explained above, the control system for the BESS system is very multifaceted and will become even more complex as regulation and functionality requirements increase. This brings us to the other aspect integrators should consider continuous support over the lifetime of the BESS, which is expected to be 20 years. This is another reason why each supplier of one of the control systems mentioned above should focus on what they are good at. BMS by the battery manufacturers, ESMS by the integrators, PPT/SCADA by the software companies, and optimizers by AI/Smart software. The mentioned systems are all connected, and their main goal is to create better and smarter energy usage. Eventually, the outcome of all the above is a better, shorter, and smoother commissioning period and better availability over 20 years.

At BLEnergy, we foresaw this need and partnered with Contel Smart Energy from day one to develop our own robust ESMS. This collaboration has already demonstrated accelerated commissioning periods, reinforcing our belief in its enduring effectiveness across projects.

In summary, adopting separate controlling systems is advantageous and important. Each system can specialize and fully focus on its designated role. BESS should have a flexible and robust ESMS for future-changing and challenging features.