With increasing penetration of distributed generation, spatiotemporally correlated uncertainties in distribution network operation become more pronounced and may cause interval overexpansion during nonlinear power flow mapping. To reduce redundant overestimation in nonlinear affine operations, this paper proposes an improved affine arithmetic method for interval power flow considering spatiotemporal correlations. First, the active distribution network is partitioned using comprehensive sensitivity-based electrical distance and affinity propagation clustering, providing the regional basis for extracting shared disturbances from the network structure. Then, based on correlation analysis, cross-correlation lag estimation, and principal component analysis, a multi-noise affine model integrating regional shared noise and node-local noise is constructed. Furthermore, first-order interval Taylor approximation and residual encapsulation are employed to reconstruct nonlinear operations, thereby bounding nonlinear remainders and constraining the propagation of newly introduced noise terms. Case studies demonstrate that the proposed method yields more compact voltage enclosures, with the improvement becoming more evident as load uncertainty increases.
With the increasing proportion of intermittent wind energy in power grids, it is generally required that the wind power generation can ride through the faults to reinforce grid resilience. In unbalanced grid fault scenarios, negative sequence voltage will induce double-line-frequency power (DLFP), resulting in extra power loss on the interfacing systems and electromagnetic torque oscillations in Permanent Magnet Synchronous Generators (PMSGs). To tackle this issue, a novel three-phase power-decoupled current source inverter (PD-CSI) is proposed in this paper. The proposed inverter can actively divert the DLFP to a ripple storage capacitor, ensuring the stable operation of the PMSG. The circuit topology and mathematical model are elaborated. The design of a simplified modulation scheme and the formulation of comprehensive control strategies are systematically discussed. Ultimately, through simulations and Hardware-in-the-Loop (HiL) experiments, it is demonstrated that the proposed circuit can achieve the active buffering of oscillatory power, reduction of the current stress on the DC-link inductor, and enhanced torque stability of PMSG against unbalanced grid faults simultaneously.
Wind farm control (WFC) can improve system stability by adjusting the power references dispatched to individual wind turbines, which is often overlooked in existing optimization studies. This article proposes a stability-oriented power dispatch optimization (PDO) strategy based on wind farm reduced-order impedance. First, a PDO model for WFC is formulated with the maximization of the stability margin of the grid-connected wind farm system as the primary objective. Second, to improve the computational efficiency of stability margin evaluation, a generalized Jordan continued-fraction expansion method is developed for wind farm impedance order reduction. Finally, a derivativefree optimization algorithm based on constrained optimization by linear approximation (COBYLA) is adopted to enable fast solution of the PDO model. Case studies are conducted on a wind farm based on doubly-fed induction generators to verify the effectiveness and computational efficiency of the proposed PDO strategy. The results demonstrate that the reduced-order impedance accurately captures the impedance characteristics of the wind farm and provides reliable stability assessment conclusions. The PDO strategy effectively enhances the stability of the grid-connected wind farm system while also contributing to reduced active power losses. Moreover, second-level control performance of the PDO strategy can be achieved by integrating reduced-order impedance with COBYLA.
The hybrid operation of grid-following (GFL) and grid-forming (GFM) converters is expected to become a prevailing paradigm in low-inertia power systems. However, the fundamentally different synchronization mechanisms and current-limiting behaviors of GFL and GFM converters lead to strongly coupled and highly nonlinear transient dynamics, making the characterization of transient stability boundaries particularly challenging. Existing studies mainly rely on numerical simulations or scenario-dependent analyses, which lack generality and scalability for heterogeneous hybrid converter systems. This paper investigates the transient stability of GFM–GFL hybrid converter systems from a stability-domain perspective. A unified transient interaction model considering current limiting constraints is established. By combining the proposed model with a reverse-time integration (RTI) approach, the attraction domain boundary of the hybrid converter system is explicitly characterized. Furthermore, an efficient method for calculating the critical clearing time is developed, enabling systematic evaluation of transient stability margins. Simulation and hardware-in-the-loop results validate the accuracy and generalizability of the proposed framework.
During low voltage ride-through (LVRT), multiple wind farms (WFs) are prone to transient synchronization instability due to power flow coupling and control interactions, which seriously threatens the security and reliability of grid-connected wind power operation. To address this issue, this paper investigates the transient synchronization stability of multiple WFs during LVRT from the perspective of active power imbalance caused by network impedance and synchronous equilibrium point existence. First, a dynamic grid-connected model of multiple WFs is established by considering the coupling effect of the common transmission line impedance, and its influence on q-axis terminal voltage dynamics is revealed. Then, based on the equilibrium point existence condition and PLL transient synchronization behavior, the impacts of line parameters and fault severity on synchronization stability are analyzed. Furthermore, a coordinated active power control strategy is proposed to regulate the d-axis active current reference of each WF, compensate for network power losses, and maintain stable synchronous equilibrium points during LVRT. The proposed strategy can significantly enhance the transient synchronization stability of multiple WFs under severe grid faults. Finally, the validity and physical feasibility of the proposed control strategy are verified through both MATLAB/Simulink and hardware-in-the-loop (HIL) experiments.
