Keeping the lights on: understanding ancillary services in power grid

With distributed generation on the rise, consumers now play dual roles as both energy producers and consumers, making the job of power system operators more complex. Stabilizing the grid amid fluctuating demand and supply—especially with unpredictable sources like rooftop solar and wind—is like balancing on a tightrope.

Ancillary services are the specialized support systems that help operators manage these shifts, protect the grid, and maintain reliable power delivery in an evolving energy landscape.

Imagine being a DJ at a huge party, ensuring the music is steady, the lights are on, and everyone’s having a good time. Just like a DJ, a power operator keeps electricity flowing smoothly despite unpredictable changes. Let’s explore what ancillary services are, how they function, and why they’re essential to the grid.

Ancillary services are specialized support functions that stabilize the grid. As electricity use fluctuates, these services keep power consistent, reliable, and safe. Just like a DJ maintains the beat, ancillary services ensure power flows smoothly, even when things go off-plan. There are several types of ancillary services, each designed to handle specific challenges within the power grid. Here’s a look at some of the most important ones:

Frequency regulation (keeping the beat steady): Electricity flows in waves at a specific frequency, typically 50 or 60 cycles per second, depending on the country. If demand for power suddenly changes—like when a bunch of appliances are switched on or off—it’s like the beat of the music speeding up or slowing down.

But for the party to be enjoyable, the beat (frequency) needs to be steady and stable regardless of who’s coming in or out of the room (appliances being switched on or off). Frequency regulation services adjust the power flow to keep this beat stable.

Spinning reserves (backup speakers on standby): At a party, speakers play the main role in delivering music to everyone. If one of your main speakers stops working, you’d want to have a backup speaker ready to take over right away, right? In the power system, “spinning reserves” serve as backup power sources.

Generators, like speakers at a party, deliver the power and energy needed to keep everything running. These reserves are on standby, ready to jump in if one of the main power generators suddenly fails.

A diagram of a system Description automatically generated

Voltage control (keeping the volume just right): When you’re adjusting the volume at a party, you want it to be just right—not too loud, not too quiet. Similarly, voltage in the grid needs to stay within specific levels (as defined in grid code) to protect appliances and electronics. Voltage control services make sure that electricity flows at a safe, balanced level, protecting equipment from damage and keeping the power quality consistent.

Black start (restarting after a power outage): Sometimes, the whole power grid can go down, similar to the music cutting out at a party. When this happens, we need a way to restart the grid from scratch. Black start services are like having an emergency generator that can bring the system back to life after a major outage. It’s the “let’s get this party going again” plan for when everything suddenly stops.

Effective management of ancillary services hinges on thorough preparation and planning. Power operators must determine the necessary backup power, the timing, and the most efficient deployment strategies. Just like a DJ preparing for a party trying to assess timing and type of guests, power system operators assess an unexpected power surge or generator failure, ensuring they’re equipped to handle such changes seamlessly.

Let’s explore how it works;

Market for ancillary services: Many power grids use an “ancillary services market,” where providers like power plants and battery storage offer services as and when needed. Operators request support and compensate these providers, similar to hiring extra help at the party.

Pricing and payments: Ancillary services auctions are tools used by grid operators to competitively obtain the resources required for grid stability and reliability. Through these auctions, grid operators can procure services from a range of providers. This competitive approach ensures access to the most cost-effective ancillary services to support grid operations. The costs of such services are borne by the consumers.

Planning for demand transitioning periods: As demand transitions from low to high—such as in the early evening when people return home and power usage spikes—grid operators must plan for this shift by securing sufficient ancillary services. This preparation ensures the grid can handle the increased load smoothly, with backup power sources ready to stabilize frequency and voltage levels. It’s akin to preparing for a sudden crowd influx at the party, ensuring everything is set to maintain a steady, uninterrupted flow.

Adjusting for renewable energy: Solar and wind energy are like unpredictable guests at a party—sometimes bringing a strong boost, other times barely showing up. Their variability adds excitement but also instability to the grid. Ancillary services help balance this, making it easier to integrate renewables while maintaining grid stability.

In conventional systems, ancillary services maintain stability for predictable power sources like coal and natural gas. In modern systems, they’ve evolved to handle the variability of renewable energy (RE) and distributed energy resources (DER).

To provide these ancillary services, advanced technologies, including battery storage and VAR compensators, are required to provide spinning reserves and handle the fluctuating nature of renewables. In Pakistan, rising rooftop solar adoption calls for a robust ancillary strategy.

Daily power swings between 500-1000 MW, within some power distribution utilities, require precise planning. Just as a DJ adapts to an unpredictable crowd, Pakistan’s system operators must manage solar variability with reliable backups, frequency regulation, and voltage control to keep everything in harmony. Pakistan’s power system operators must deploy a strategic mix of ancillary services to maintain balance, ensuring that the “party” on the grid never stops, and the lights stay on.

Copyright Business Recorder, 2024