This article is the first part of a three-part blog series titled Battery Energy Storage Systems in Electricity Markets. The series explores how battery energy storage systems (BESS) operate in electricity markets, how they are integrated into reserve markets, and practical experiences from testing different ancillary services. In this first part, we focus on BESS from the perspective of electricity markets.
Battery energy storage systems from an electricity market perspective
Battery energy storage systems have become a key element in the ongoing transformation of electricity markets. Flexibility has become one of the most important characteristics of modern power systems. However, in practice, flexibility is not achieved through battery capacity alone. The critical factor is how the entire system is designed, controlled, and integrated into both the power system and electricity markets. This is where differences between BESS solutions become evident.
At Syncron Tech, we have been involved in several battery energy storage projects in recent years. Based on our experience, the technical implementation plays a decisive role in project success. A common assumption is that a battery system can be directly connected to Fingrid’s reserve markets. In practice, the situation is more complex. There are significant differences between battery technologies and system implementations, for example in response times, control accuracy, and controllability. These characteristics ultimately determine whether the system meets market requirements and passes the required compliance testing.
These challenges typically become visible during the grid compliance assessment process. This is not about a single requirement, but a combination of several aspects, including frequency and voltage support, measurement systems, protection schemes, and real-time communication. In many projects, it becomes clear at this stage that inverter-level control alone may not be sufficient.
PPC as the bridge to electricity markets
At this point, the control system becomes essential, particularly the Power Plant Controller (PPC). Centralized plant-level control enables the entire facility to be operated as a single coordinated system, implementing the control logic required by Fingrid and adapting to the requirements of different reserve markets. It also enables reactive power capability at the point of connection and supports required market communication interfaces. In practice, the PPC acts as a bridge between the technical system and electricity markets.
The overall solution matters
Recently, attention has also been drawn to the practical operation of battery systems. Reserve markets require fast power changes, which means continuous switching between charging and discharging and steep ramp rates. However, overly aggressive control strategies can accelerate battery degradation, reduce performance, and in the worst case impact warranty conditions. Therefore, a balance must be found between market optimization and technical lifetime performance.
In many projects, a workable approach has been to keep the core BESS delivery relatively lean, while complementing the overall system with a dedicated PPC solution. This provides the necessary flexibility without overengineering the entire installation. At the same time, it improves interoperability between different stakeholders, such as traders, control centers, and grid operators.
It is also important to note that grid code requirements are extensive, and it is not always practical to implement everything in-house. Competent partners therefore play a key role throughout different phases of the project. When system architecture, control strategy, and market requirements are considered as a whole, a battery energy storage system becomes more than just a physical asset — it becomes an active and value-generating part of the power system.
The blog series continues in the autumn with new topics. The following parts will focus on bringing battery energy storage systems into reserve markets and practical experiences from testing different reserve products.
Have a great summer.
