Primary Frequency Response

Sudden imbalances between generation and load in transmission, distribution, and isolated grids can cause frequency variations that risk stable delivery of electricity within the electrical utility system.

Traditional synchronous generating resources such as fossil and nuclear power plants have historically provided adequate levels of inertia to limit this frequency variation. But what happens when fossil and nuclear plants are retired, and additional non-synchronous renewable generating resources such as solar and wind are added to the grid?

The result is a low inertia grid. In the new global generation mix where the loss of traditional fossil and nuclear generation plants is being replaced by renewables, there is an increased rate of change of frequency (RoCoF) where grid disturbances cause load shedding, system tripping, and an increased risk for unintended short and longer term power drop-outs.

Energy storage technologies, including ultracapacitors (supercapacitors), provide synthetic inertia to utility grids and microgrids to ensure frequency and power system stability. During frequency deviations away from utility set points, ultracapacitors provide ultra-fast synthetic inertia (with a response rate measured in cycles) to the system by rapidly injecting power thus mitigating fast RoCoF events and out-of-limits frequency deviations.

Ultracapacitors and fast responding inverters set in frequency sensitive mode can stabilize frequency excursions in grids and microgrids by rapidly injecting or absorbing power in the milliseconds timeframe, with continuous power delivery scalable to traditional primary response time durations. This provides immediate response to the imbalance before slower assets can react.

Frequency Stabilization Timescales and Ultracapacitor Response

Ultracapacitor Power Injection in Response to Frequency Deviation

Example System Architecture: AC Coupled


Generate optimized business cases for projects

Let us work with you to develop your energy storage business case.

  • Response time: Maxwell ultracapacitor systems can deliver stored energy at full power in the cycles timeframe and ensure availability for market participation.
  • Footprint: The high power performance of ultracapacitors enables significant reduction in storage system footprint versus battery systems for high power density applications.
  • Long operating life and opex reduction*: Maxwell ultracapacitor systems typically provide a 12 to 15-year lifetime with no replacement cycles. Ultracapacitors are electrostatic devices designed to be repeatedly charged and discharged in full cycles or micro-cycles. Maxwell’s ultracapacitors have demonstrated over 1 million benchmark charge-discharges.
  • Capex reduction: Ultracapacitors are electrostatic devices that do not need to be 1-5x oversized to meet power requirements. In many cases, minimal to no balance of plant cooling is required because the devices have a wider operating temperature window and are not as prone to ESR rise (heating) as batteries.
  • Hybrid systems: Maxwell ultracapacitor systems act as a buffer on the battery to mitigate degradation caused by heating from repeated fast cycling. This preserves battery lifetime and reduces the number of battery replacement cycles to reduce opex.
*Results may vary. Additional terms and conditions, including the limited warranty, apply at the time of purchase. See the warranty details and datasheet for applicable operating and use requirements.

Please visit our product page for an overview of the system.

Contact Us

Established in 1965, Maxwell Technologies has been a trusted supplier of high-tech energy solutions for customers worldwide. Over the past 20 years, system designers across industries have leveraged the power and speed of Maxwell’s ultracapacitor cell technology. Maxwell’s quality and proven field reliability is evidenced in the over 8 million devices provided to grid applications and 65 million ultracapacitors deployed in systems for automotive, heavy transportation, renewable energy and industrial applications.

Contact us using the form below and let us know how you would like to proceed.