Researchers at ETH Zurich have patented a grid-forming inverter algorithm that stabilizes frequency while protecting devices from damage by independently controlling frequency, voltage, and current.
From pv magazine Germany
A research team from Swiss research institute ETH Zurich has created a new algorithm for operating inverters in a grid-forming mode.
The patented algorithm operates the inverter as a voltage source, which is critical when short circuits and voltage drops complicate grid operation.
Traditionally, power plants using steam turbines to drive generators – particularly nuclear, coal-fired, and gas-fired plants – have set and maintained grid frequency. As such plants are phased out, the grid will require new operating modes for inverters in PV systems, battery storage, and wind turbines.
These inverters must function as voltage sources or clock generators. However, that behavior is difficult to implement, especially during faults. In the event of a sudden voltage drop in the grid, inverters – unless properly controlled – attempt to maintain output by feeding more power into the system, risking damage to their electronics. To prevent this, they typically shut down during faults.
With this in mind, a team led by Florian Dörfler, professor of complex control systems at ETH Zurich, developed an algorithm that stabilizes frequency without damaging the device. Maitraya Desai, Dörfler’s doctoral student, identified that grid voltage and alternating current frequency should be controlled independently during faults.
The proposed control algorithm follows this principle, keeping frequency stable under all conditions. It limits current while allowing voltage to fluctuate freely.
The team tested the algorithm in computer simulations. Because it is implemented as software, they also successfully validated it on a laboratory test system without needing a new test environment.
Next, Dörfler and his team plan to partner with companies to implement the control algorithm in real-world applications and integrate it into new software products.