Grid stability |
UD-STATCOM, a “shock absorber” for oscillations
Active damping that stabilises the network without expending energy or curtailing generation. This simple idea, with its far-reaching implications, is realised in Ramboll’s Universal Damping STATCOM (UD-STATCOM), patent pending. It can eliminate a primary cause of global power grid instability: too many different power sources added to an ageing energy infrastructure – a growing problem that likely contributed to the Iberian outage of April 2025
Dr Mojtaba Mohaddes Senior Technical Manager at Ramboll
The modern power system is transforming faster than ever before. Electrification of heat and industry, accelerating data centre demand, and the rapid build-out of renewables are reshaping how, where, and when electricity is produced and consumed. This evolution brings immense opportunity, but also introduces a critical technical question: how do we manage oscillations in an increasingly dynamic grid so that stability keeps pace with change? The answer to that question is complex. It’s clear that we need to expand generation capacity and increase transmission capability. But the options for doing so aren’t always simple. New transmission corridors are scarce, costly, and, often, come with burdensome technical and regulatory requirements. While underground and subsea cables may help, they offer their own set of engineering challenges.
As the industry becomes more and more dependent on renewables, often inverter-based resources (IBR) like solar, wind, and battery storage, we find another issue in that the geographical pattern of generation is shifting as renewables replace centralised fossil fuel assets. These new renewable sources are often located far from legacy infrastructure and output profiles can change on an hourly basis. The pattern of power flow from generation to load keeps changing its shape and that means our transmission network needs to be flexible enough to deal with these variations on a seasonal, if not daily, basis.
Added to all of this is the complexity of controlling such a network when there are so many sources of power, each with its own powerful controls. And they must all work in harmony. If the controllers aren’t aligned, they can oscillate against each other, causing instability. The variability of renewable generation further stresses this complexity. As wind and solar output rise and fall outside our direct control, the system’s balance must be maintained in real time. That raises the value of energy storage and fast controls that can respond to dips and surges. But it also increases the demands placed on co-ordination and damping. In short, we are not merely building more grid; we are evolving from a predictable, largely synchronous system into a dynamic, digital, multi-controller infrastructure. If the industry doesn’t adapt quickly, the consequences could be rising instability and more frequent blackouts. Operators, utilities,
Fundamental operating concept of the UD-STATCOM. The three-phase bus voltages are measured, and their fundamental frequency components are taken out. The remaining voltage signals represent oscillatory modes that require damping. The reference currents for the VSC are then computed by dividing these unwanted residual voltages by an equivalent resistance, Req
and regulators all share a stake in addressing this challenge.
A simple device offers a solution In thinking about that original question, how do we manage oscillations, an idea came to me that I wasn’t able to ignore – a device that continuously “listens” to the grid, detects the onset of oscillations across a broad frequency range, and responds instantly by absorbing energy from
the oscillatory mode – just like a shock absorber on a car. Once that excess energy is captured, it does not go to waste; the device returns it to the system at the fundamental power frequency (50 or 60 Hz). The result is active damping that stabilises the network without expending energy or curtailing generation. It’s a simple idea with far- reaching implications.
. Image: Ramboll
The technology, called Universal Damping STATCOM (UD-STATCOM) can be delivered as a new, stand-alone device or implemented as a software-enabled extension of an existing STATCOM. In the latter case, the STATCOM retains its normal reactive power and voltage control function, but the damping capability kicks in the instant oscillations appear. That means asset owners could leverage installed infrastructure and add stability functionality largely through software, accelerating deployment and lowering cost. However, there are real-world integration challenges. Current STATCOM fleets span multiple generations and manufacturers, each with distinct control architectures and firmware. Enabling damping functionality will require collaboration case by case, and in some instances the involvement of OEM engineers
PSCAD SIMULATIONS, DEMONSTRATING UD-STATCOM IN ACTION. Images: Ramboll
A wind farm connected to the grid via a series-compensated transmission line becomes unstable when a step change occurs in wind speed (note growing oscillations in speed, active and reactive power).
26 | April 2026 |
www.modernpowersystems.com
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