Rotating Grid Stabilizer Conversion

How renewable energy trends affect grid stability

With the rising adoption of renewable energy, traditional power generation methods are utilized less, and generators are being shut down.

Once these generators are shut down, their role in providing rotational inertia, short circuit power and voltage control, to help balance the grid system disappears with them also. Grid stability is therefore a vital consideration for transmission and distribution network operators, with increasing renewable penetration.

The good news is that existing power plants can provide rotating grid services without burning fossil fuels. 

What are the benefits of Rotating Grid Stabilizer Conversion (RGS)?

With the Rotating Grid Stabilizer (RGS) Conversion solutions, you can convert your existing power plant assets to a synchronous condenser to achieve grid stability. By utilizing power plants that may otherwise become stranded assets, RGS conversions provide necessary system inertia, short circuit power and reactive power to the grid for that balance. 

Inherent frequency response, the result of system inertia, is the ability of an electrical machine to absorb and store or inject energy in order to manage frequency. One way to do this is to use technology with a rotating mass, like flywheels and synchronous condensers, to store energy for short-term frequency support. This helps to prevent blackouts, due to a rapid change of frequency and maintains a stable grid, within its frequency limits. 

You can also generate additional revenue streams by providing additional active power with our hybrid conversion solution.


Rotating Grid Stabilizer with a flywheel at Killingholme

Image of the Rotating grid stabilizer installed at Uniper's Killingholme power station in UK

At the Killingholme site, Uniper repurposed two retired steam turbine generators and installed flywheels to deliver essential grid stabilization services to National Grid ESO.

How is grid stability maintained?

Traditionally, grid stability is achieved through the dependence on the system strength and system inertia. System strength refers to the ability of the electricity grid to recover intact from major disturbances and it is provided by the short-circuit power of the generator or synchronous condenser. The same generator also provides system inertia which is critical to maintaining a steady frequency in the grid. And no matter the source of generated power, electrical grid systems rely on both for grid security, safety, and reliability.

By spinning continuously, a Rotating Grid Stabilizer provides inertia, dampening fluctuations in the grid frequency. Watch the video to learn more.

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Three ways to convert your generator to a Rotating Grid Stabilizer

Our conversion approach is tailored to meet your needs. Building new infrastructure is one option, but the infrastructure that is already in place can be repurposed as well. Typically, we begin the project with a feasibility assessment to determine whether your assets can be converted to a Rotating Grid Stabilizer (RGS). The next step is to initiate a Front End Engineering Design (FEED) study in order to achieve a successful RGS conversion.

Basic RGS conversion

Icon of RGS basic conversion

The basic conversion provides a cost-optimized solution that converts existing turbogenerators into synchronous condensers quickly. We will also take care of installing a tailor-made solution for startup and accelerating the generator.

Flywheel conversion

image of a flywheel from Siemens Energy

Generators can be extended with additional rotating mass from a flywheel to provide maximum inertia. Flywheels are operated in a partial vacuum and equipped with a cooling system to minimize friction losses and reduce cooling efforts.

Hybrid conversion

icon of hybrid RGS conversion

For maximum flexibility, you can couple a gas or steam turbine with an additional SSS (Synchro-Self-Shifting) clutch between the generator and the turbine. The option also exists to add additional inertia with a flywheel coupled to the existing shaft line.

Learn more about RGS conversion

With our Rotating Grid Stabilizer (RGS) conversion, you can maintain your competitive edge while avoiding stranded assets. Have we piqued your interest? Get in touch with us today to learn more.

Fundamentals of grid stability

Grid stability is what keeps the challenges to power systems, such as the spikes or lulls in demand, power line, or even generator failure, in check. Since power is produced on demand, it's critical to ensure that the power system frequency and voltage remain within normal ranges. Maintaining this balance is necessary to keep the power grid stable and efficient.

To ensure the grid remains stable and secure, it is essential to balance the electricity grid through frequency stabilization, short circuit power, and voltage control. Flexibility stabilization happens when system inertia responds to sudden load imbalances. The inertia delays the Rate of Change of Frequency (RoCoF), so downstream grid stability controls can be executed.

Grid inertia is the ability of a power grid to absorb changes in frequency without destabilizing the system. It is the key factor for maintaining grid stability.

Short circuit power contribution is the ability of an electrical machine to inject high levels of current during a grid short circuit event, to ride through the fault and maintain a stable grid.

Voltage control is the ability to inject and absorb reactive power to ensure a stable system voltage. This helps to reduce the voltage drop caused by the short circuit, limit the short circuit current, and quickly restore the power system's stability. It also enables keeping the system voltage within an acceptable range.