Comparison between AGC and a tuningless LFC approach based on direct observation of DERs

Automatic Generation Control (AGC) used in secondary frequency control requires manual tuning to maintain a balance between reaction speed and stability. This task becomes increasingly difficult due to the rising number of inverter-coupled devices and High-Voltage Direct Current (HVDC) links, and the resulting reduction of available inertia. In this paper, we propose a tuningless Load-Frequency Control (LFC) approach able to cope with the changing dynamics of electric power grids. Harnessing the possibilities of modern monitoring and communication means, the so-called Direct Load-Frequency Control (DLFC) employs two concurrently operating processes: a power matching stage responsible for secondary power adjustment using directly observed area imbalances; and a frequency control stage that adjusts primary reserves' frequency setpoints in a systematic manner. As opposed to the AGC, the DLFC does not require an integrator to mitigate frequency deviations. The only free parameter is the secondary control interval, from which all other parameters are derived. Small-signal stability investigations show that the DLFC exhibits 40 dB falloff of steady-state deviations versus the AGC's 20 dB. Simulations on the non-linear singlearea system confirm the DLFC's response speed and stability advantage.