This article presents a novel measurement-based frequency regulation scheme that utilizes the contributions of inverter-based resources (IBRs). IBRs are assumed to be aggregated within dynamic virtual power plant (DVPP), conceptualized as a new entity in modern power systems that can be summoned by the system operator to provide dynamic ancillary services. While the participation of DVPPs in frequency regulation is outlined in ancillary service markets, the main objective is to distribute regulation signals among the resources within DVPPs. To achieve this, a power imbalance propagation paradigm is introduced, aiming to estimate the extent of power imbalance across the grid. Subsequently, the contribution factor is established for the purpose of evaluating the involvement of individual clusters of IBRs within the context of both primary and secondary frequency control commitments. The proposed mathematics-based approach is scalable and only needs to have access to few local measurments and exchanged power information between the adjacent neighboring areas to realize a real-time application. The effectiveness of the proposed methodologies is examined on two power grids.

A novel control scheme based on a new stochastic equivalent model of the power system, which provides flexible inertia constant to enable high penetration levels of Microgrid (MG) generation is proposed. The approach combines an adaptive Energy Storage System (ESS) dispatch strategy with an MG controlled islanding scheme to provide frequency support for the host power grid. First, a Center-of-Gravity (COG) formulation of the inertia-control scheme is proposed, in which the unbalance torques between the control areas and the COG are used to reduce frequency deviations. An application example-based equivalent model of ESSs as seen from the grid side is then proposed that takes advantage of the ESS special attributes to contribute to inertial response. Simulation results on two test systems demonstrate the efficiency of the proposed control scheme to increase the host grid ability to efficiently integrate multiple MGs. Numerical tests suggest that the proposed control scheme increases system penetration level at least by 12%, which justifies the use of inertia emulation techniques to accommodate higher levels of distributed generation.

This paper presents a measurement-based under-frequency load shedding scheme that considers time delays, measurement uncertainties, and communication network faults. Using a moving first-degree polynomial function, an iterative approach to estimate the frequency nadir and the associated frequency nadir time is proposed. Then, a novel method to simultaneously estimate the power imbalance and the system inertia constant is developed. According to an analytical basis, a base system is selected from a set of pre-defined base systems to guarantee accurate power imbalance estimation. Finally, a mathematical index is investigated to calculate a threshold for the generation-load power imbalance beyond which loads should be shed. Further, a systematic approach for specifying the amount of load to be shed in each transmission bus of the system is proposed. The effectiveness of the proposed methodologies is examined on both simulated and actual measured data from 9 historical power system disturbances in a national power grid.

A novel approach based on the notion of center-of-gravity (COG) dynamics in mechanics is used to estimate local and global power system's frequency behavior. In this framework, the power system dynamic behavior is represented by an equivalent model in which the geographical areas interact with the COG through fictitious interconnectors from which the inherent dynamics of power frequency transients is explained using fundamental physics principles. The relationship between the frequency of the COG and the motion of local centers of angle is determined and expressions to compute local frequency deviations following major disturbances are derived. Detailed simulation results on three test power systems are used to demonstrate the accuracy and flexibility of the proposed method under both, N-1 and N-2 contingencies.

To analyze the grid integration effect of a virtual synchronous generator (VSG), this paper proposes a simple power system modeling method. It is shown that for a specific disturbance, by simplifying the original network to a radical n generators single-load model, its state-space small-signal model can be obtained using a unified formula, as long as the single generator infinite bus model of each generator is given. Case studies based on the IEEE 9-bus test system as well as the New York New England test system show high efficiency of the proposed modeling to represent slow power and frequency deviations. Modal analyses give insight into how system poles are synthesized by individual generator poles, and how different designs of VSGs affect the system oscillation modes. Potential errors due to the topology simplification and the measures to avoid them are discussed. The time-domain results and modal analyses highlight some important features of VSG, which are overlooked in previous studies.