Parameter Estimation of First-Order Frequency Response Model for AC Distribution Networks with Hydro-Energy Storage

To address the frequency response modeling problem of AC distribution networks with hydro-energy storage, a parameter estimation method for a first-order frequency response model based on the nonlinear least-squares technique is proposed in this paper. First, by analogy with the swing equation of synchronous generators, a first-order frequency response model of the AC distribution network is established, which is capable of reflecting the overall external characteristics of the hydro-energy storage system. Then, based on the post-disturbance frequency data, the dominant decay coefficient and the steady-state frequency deviation are estimated using the nonlinear least-squares method. Subsequently, the inertia time constant is further obtained through the inverse proportionality relationship between the dominant decay coefficient and the inertia time constant. Finally, an electromagnetic transient simulation model of the AC distribution network with hydro-energy storage is built in PSCAD/EMTDC, and the effectiveness of the proposed frequency response model and its parameter estimation method is verified by multiple sets of simulation results.