Understanding the 2 Fundamental Limitations of Conventional BESS Control Systems

Most battery energy storage systems (BESS) in operation today are underperforming. For operators tasked with meeting BESS revenue goals, underperformance is a considerable, enduring challenge. 

But the cause of underperformance isn’t faulty batteries; it’s inherent flaws in conventional BESS control systems.

These are the two fundamental limitations of conventional BESS control systems and how they negatively impact your BESS asset availability, performance, and revenue generation. 

2 limitations of conventional BESS control systems

The two fundamental limitations of conventional BESS control systems are unknown imbalance levels and inaccurate state estimates. Together, these unreliable estimates limit availability, undermine performance, and impair profitability. 

1. Unknown imbalance levels

When individual battery cells within a string develop unequal States of Charge (SoC), the result is cell imbalance. This is one of the most well known and persistent challenges in BESS operations; yet, conventional BESS control systems do little to overcome the problem. 

In fact, with typical BMS (Battery Management Systems) and EMS (Energy Management Systems), operators get little to no insight into battery racks’ or blocks’ balance states. These unknown imbalance levels have significant consequences for BESS asset availability, performance, and profitability. 

2. Inaccurate state estimates

Accurate, real-time estimates of energy and power are critical to successful BESS operations. These state estimates (e.g., SoC (State of Charge) and HSL (High Sustainable Limit)) directly influence market participation strategies, operational decisions, and eventual BESS asset revenue generation. 

However, despite their crucial role in BESS operational success, most native BMS/EMS estimates are inherently untrustworthy, leaving asset operators working with estimation error rates of 15%, sometimes as high as 90%. 

How unknown imbalance levels and inaccurate state estimates undermine BESS availability, performance, and revenue generation

Unknown imbalance levels and inaccurate state estimates aren’t insignificant technical flaws. In practice, they erode BESS asset availability, performance, and revenue generation. 

First, unknown imbalance levels render any balancing strategy both inefficient and ineffective. 

If operators don’t have access to accurate imbalance levels, it’s nearly impossible to correctly balance assets—and both overbalancing and underbalancing lead to undesirable results. If you overbalance, you create excessive downtime and leave money on the table. But if you  underbalance, you allow underperformance to persist. 

Either way, balancing BESS assets based on unknown imbalance levels reduces availability and limits opportunities for revenue generation. 

Relying on inaccurate state estimates further upsets BESS operations. 

With too high energy and/or power estimates, you risk setpoint deviations and the financial penalties of failing to deliver on market commitments. Conversely, with too low energy and/or power estimates, you compromise profitability by leaving surplus energy and dispatch power unused. 

Conclusion: You’re losing money with conventional BESS control systems.

Unknown imbalance levels and inaccurate state estimates are more than small technical flaws. They significantly weaken asset availability and performance, ultimately stifling profitability. 

Unfortunately, these limitations are inherent to conventional BESS control systems—but there are now solutions to overcome them. 

Zitara Balance is an on-premise algorithm that monitors cell-level raw data inputs to produce accurate, real-time balance/imbalance signals at the rack level. Zitara Power, meanwhile, produces accurate, real-time control signals, such as SoP (State of Power), SoE (State of Energy), etc.) 

Together, these two software modules make up Zitara for BESS, the solution designed to overcome the two fundamental limitations of BESS control systems, enabling smarter balancing and more accurate state estimates to help asset operators improve BESS availability, performance, and profitability. 

Learn more about how to get more from your BESS assets in our new technical white paper.