How Do Battery Systems Maintain Grid Frequency?

When a heat wave hits and entire cities crank up their air conditioning simultaneously, we rarely think about what keeps our electrical grid humming at exactly the right frequency. But grid frequency is critical – too high or too low, and the entire power system becomes unstable. Traditional power plants use massive spinning turbines to maintain this balance, but they’re slow to respond when demand suddenly spikes or drops. That’s one of the many great benefits of battery systems – it can react in milliseconds to stabilize the grid.

In this clip from the free course “Introduction to Software for Battery Systems,” Peter Gruenbaum explains grid frequency and why battery systems are ideal for frequency response services. To learn more about battery system software, enroll in the free course.

Transcript below.

 So let me explain frequency response. Most energy generators use turbines – natural gas, coal, nuclear power, and hydroelectric power – they all use turbines. The basic physics principle is that if you run a wire loop through a magnetic field and spin it, then current will run through the wire. It’s alternating current where the frequency of the voltage is equal to the frequency of the spinning turbine.

How hard it is to turn that wire depends on how much electrical load you have. So if suddenly thousands of people turn on all their air conditioners, the load will increase and it becomes harder for the turbines to spin, and therefore the frequency drops. Similarly, if a power station suddenly goes out and the load becomes much less, the frequency will suddenly rise.

Batteries can dump power into the grid if the frequency suddenly drops to bring it up or pull power from the grid if the frequency suddenly rises to bring it down. And the beauty is that batteries can react in milliseconds unlike turbine based generators.

This chart shows a common way that frequency response operates for a system where the ideal frequency is 60 hertz. If the frequency is between 59.8 and 60.2 hertz, then the batteries don’t do anything. If it drops below 59.8, then the batteries start putting in power. The more it drops, the more power it adds to the grid.

If the frequency drops below 57.6 hertz, then the battery puts out the maximum amount of power that it offered, but doesn’t go any higher than that. Similarly, if the frequency rises above 60.2 hertz, then the battery takes in power and the amount of power increases linearly until it reaches 62.5 hertz, in which case, it only takes in the maximum amount of power that was offered.

Different markets will use different numbers, and many countries have an ideal frequency of 50 hertz instead of 60.