Stabilizing the Grid

Prafull Jaltare

Co-Founder KNOPOWER Power System Academy

I came across an interesting article in Siemens Energy Magazine recently about their E-STATCOM product for grid stabilization. Indeed the advent of renewables and Small Modular Reactors is changing the nature of power grid from large monolithic interconnected grid to micro grids, fragmented grids, isolated grids with can operate in an autonomous manner as well as integrated manner thru tie lines and FACTS controls. While this flexibility has many advantages such as near load generation, avoidance of long distance transmission, infrastructure cost reduction of transmission and distribution equipment, reduction of transmission and distribution losses, reduction of carbon foot print due to use of renewals etc., but it has a side effect that needs to addressed, that of grid stability. Some of my observations on this topic and how KNOPOWER courses can help in understanding, analyzing and choosing between alternate solutions to these new type of problems in the grid are jotted down.

To quote from President Siemens Energy North America in the magazine:

Higher levels of renewable energy like wind and solar power are being added to our electrical grid, and synchronous condensers can feed into a grid to balance the volatility of power supply provided by these intermittent resources.

Why is Grid stability increasingly becoming a concern now a days.

With the increase of feed from renewable Energy resources like Solar and Wind in to the grid, the percent contribution from old and large power plants with high mechanical inertia is reducing day by day. Many large Nuclear and Fossil power plant are being phased out. Though it has significant positive impact on reduction in carbon emission etc but it is reducing the stability of voltage and frequency of the grid.

To quote from Siemens Energy Magazine why its happening:

For decades, traditional power plants, such as coal and nuclear, provided more than electricity. Their massive spinning generators acted as stabilizers, keeping grid frequency locked at 50 hertz. If demand spiked or a generator tripped offline, the kinetic energy of these spinning masses provided a buffer, like a shock absorber, giving grid operators precious seconds to respond.

Those seconds often meant the difference between a stable grid and equipment damage, cascading outages, or even a nationwide blackout. But now, as Europe and the world race toward carbon neutrality and phase out conventional plants, that stability has become harder to maintain."

Understanding the problem

The situation of stability of a power grid of yesterday and today can be compared with an analogy of a large car/ship/plane/vehicle with their smaller versions. Bigger the vehicle, higher its stability will be due to its large Inertia and stored kinetic energy in it. A small bump on road or a wave in sea or an turbulence in air will cause a significant impact on the smaller vehicle whereas large vehicle will easily absorb the impact so that a passenger sitting inside will hardly feel it. Smaller vehicle will tend to vibrate or go out of control for a small bump. Situation is similar in a large power grid having large power plants with high inertia rotating equipment and modern grids with small renewable generators like wind turbine and solar panels. Large machines and interconnected grids supply or absorb the momentary disturbance in the grid such as switching on or off a large load of few hundred mega watts or a tripping of a large generator of say few hundred megawatt capacity. Where as modern grids are very sensitive to such disturbances.

Mitigating the problem

The sensitivity of grid frequency and voltage to grid disturbance could be reduced by adding large Synchronous Condensers in the grid at strategic locations which are like Synchronous Generators without any turbine input. These synchronous machines have field windings like a generator, which can control the terminal voltage by changing the excitation in both lead and lag direction. This improves the voltage stability and the large inertia of rotating mass of generator adds to the frequency stabilization effect. In fact additional rotating mass is added to these synchronous condensers such as large fly wheels to increase the inertia and there by the frequency stability of the grid. This was first tried 5 years ago. Please see an old article. However synchronous condenser solution is an expensive one, requiring synchronous machines and excitation systems.

Other solution is a static one such as E-STATCOM from Siemens. These store energy in large capacitor banks and statically release it in the grid in response to frequency and voltage disturbances due to load generation imbalance sensed by control system. In the Vehicle analogy, this is similar to storing hydraulic energy in large hydraulic tanks using displacement pumps and releasing this energy in shock absorbers of the vehicle using sophisticated software algorithms which sense the vibrations of the vehicle and release the energy stored in hydraulic tanks to assist the shock absorbers to stabilize the vehicle such that the impact and vibrations to the vehicle are minimized.

How KNOPOWER training can help in analyzing the problem

KNOWPOER has a large training module coming up on power system stability, which gives insights in the aspects of grid frequency and voltage oscillations due to load generator imbalance. These studies are becoming more and more important for studying and designing islanding schemes, designing stabilizing schemes such as synchronous condenser locations and sizes as well as sizing static equipment like E-STATCOM. This training module will enable you simulate and analyze the grid stability and to simplify and approximate large systems into small and manageable systems and come out with best techo-commercial solution to the problem of grid stability in the modern grids which is becoming more and more difficult and relevant.

Originally published Dec 11, 2025

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