Min Xiong

Electromagnetic transient simulation plays a crucial role in power system transient stability analysis, but traditional numerical integration methods such as the trapezoidal rule method and the Euler method are time-consuming due to the small and fixed time steps. To improve efficiency, this paper proposes a novel generalized high-order nodal formulation for electromagnetic transient simulations. The method generalizes and extends the traditional companion circuit method to achieve any high-order accuracy. By utilizing a multi-stage diagonally implicit Runge-Kutta method, the corresponding companion circuits of network components are derived. Then, a recursive computation process is proposed to solve the network equation without rebuilding the conductance matrix with multi-stages in a time step. The high-order nodal method allows for larger time steps without sacrificing accuracy. Case studies on a four-bus and an 1170-node system compare the computational efficiency of the proposed method with different orders.

As inverter-based resources (IBRs) penetrate power systems, the dynamics become more complex, exhibiting multiple timescales, including electromagnetic transient (EMT) dynamics of power electronic controllers and electromechanical dynamics of synchronous generators. Consequently, the power system model becomes highly stiff, posing a challenge for efficient simulation using existing methods that focus on dynamics within a single timescale. This paper proposes a Heterogeneous Multiscale Method for highly efficient multi-timescale simulation of a power system represented by its EMT model. The new method alternates between the microscopic EMT model of the system and an automatically reduced macroscopic model, varying the step size accordingly to achieve significant acceleration while maintaining accuracy in both fast and slow dynamics of interests. It also incorporates a semi-analytical solution method to enable a more adaptive variable-step mechanism. The new simulation method is illustrated using a two-area system and is then tested on a detailed EMT model of the IEEE 39-bus system.

The increasing penetration of inverter-based resources (IBRs) introduces new challenges to power system simulations, particularly with the emergence of fast electromagnetic transient (EMT) dynamics and sub-synchronous oscillations (SSO) that require time-consuming EMT simulations. To reduce the time cost for simulating a large-scale power grid with IBRs, this paper proposes a novel participation factor-based approach for defining a critical zone for detailed EMT modeling and simulations, which includes the IBRs, synchronous generators, and the network components participating significantly in simulated contingencies. Both model-based and response-based methods are introduced for the estimation of participation factors (PFs). The case study on the 240-bus Western Electricity Coordinating Council (WECC) system demonstrates that the EMT zone determined by the proposed approach can effectively capture power system dynamics involving IBRs.

The escalating integration of inverter-based resources (IBRs) poses new challenges to power systems by introducing fast dynamics with higher frequencies, which may need to be simulated by an electromagnetic transient (EMT) program. As an alternative to conducting EMT simulations for the entire system, which is typically time consuming, hybrid simulation between EMT and phasor-domain transient stability (TS) can greatly reduce the computational burden while preserving the detailed fast dynamics in the EMT zone. This paper establishes an EMT-TS hybrid simulation platform using open-source tools, specifically ParaEMT, GridPACK, and HELICS, which are the EMT simulator, TS simulator, and interface framework, respectively. Case studies on the 240-bus Western Electricity Coordinating Council (WECC) system demonstrate that the developed ParaEMT-HELICS-GridPACK hybrid simulator can accurately capture both slow electromechanical and fast IBR-driven dynamics with a 2.4× speedup.

Power engineers rely on computer-based simulation tools to assess grid performance and ensure security. At the core of these tools are solvers for sparse linear equations. When transformed into a bordered block-diagonal (BBD) structure, part of the sparse linear equation solving can be parallelized. This work focuses on using the Schur-complement-based method for LU factorization on BBD matrices, specifically, Jacobian matrices from large-scale systems. Our findings show that the natural ordering method outperforms the default ordering method in computational performance for each block of the BBD matrix. This observation is validated using synthetic 25k-bus and 70k-bus cases, showing a speedup of up to 38% when using natural ordering without permutation. Additionally, the impact of the number of partitions is studied, and the result shows that computational performance improves with more, smaller partitions in the BBD matrices.

This paper proposes a semi-analytical approach for efficient and accurate electromagnetic transient (EMT) simulation of a power grid. The approach first derives a high-order semi-analytical solution (SAS) of the grid’s state-space EMT model using the differential transformation (DT), and then evaluates the solution over enlarged, variable time steps to significantly accelerate the simulations while maintaining its high accuracy on detailed fast EMT dynamics. The approach also addresses switches during large time steps by using a limit violation detection algorithm with a binary search-enhanced quadratic interpolation. Case studies are conducted on EMT models of the IEEE 39-bus system and large-scale systems to demonstrate the merits of the new simulation approach against traditional numerical methods.

The electromagnetic transient (EMT) simulation is an essential tool for studying power grids dominated by inverter-based resources (IBRs). However, due to small simulation time steps and increasing problem sizes , performing EMT simulations for large-scale power grids becomes computational-intensive, and often impractical. To address this challenge, we developed ParaEMT, an open-source Python-based EMT simulator that is parallelizable and compatible with high-performance computing (HPC) systems for simulating large-scale power grids with a significant presence of IBRs. Its key features include: 1) utilizing parallel computation for network solution by decomposing the network conductance matrix into the bordered block diagonal form; 2) enabling parallel updates of device states and network historical currents; 3) leveraging HPC to further accelerate simulation through a developed generic interface. The accuracy of ParaEMT has been validated on the reduced 240-bus (720-node) Western Electricity Coordinating Council system by benchmarking the EMT dynamics against PSCAD. Furthermore, ParaEMT achieves a notable speedup of approximately 25 to 36 times on a synthetic 10,080-bus (30240-node) system by leveraging the HPC resource named Eagle at the National Renewable Energy Laboratory. A regional 100% renewable case of the reduced 240-bus system has been developed for simulating system-wide IBRs’ interactions in large-scale power grids using ParaEMT.

Traditional dynamic security assessment faces challenges as power systems are experiencing a transformation to inverter-based-resource (IBR) dominated systems, for which electromagnetic transient (EMT) dynamics have to be considered. However, EMT simulation is time-consuming especially for a large power grid because the mathematical model based on detailed component modeling is highly stiff and needs to be integrated at tiny time steps due to numerical stability. This paper proposes a heterogeneous multiscale method (HMM) to address the simulation of a power system considering EMT dynamics as a multiscale problem. The method aims to accurately simulate the macroscopic dynamics of the system even when EMT dynamics are dominating. By force estimation using a kernel function, the proposed method automatically generates a macro model on the fly of simulation based on the micro model of EMT dynamics. It can flexibly switch between the micro-and macro-models to capture important EMT dynamics during some time intervals while skipping over other time intervals of less interest to achieve a superior simulation speed. The method is illustrated by a case study on a two-machine EMT model to demonstrate its potential for power system simulation.

This paper proposes a data-driven approach for estimating participation factors for a power system using only simulation results on selected disturbances. The approach is purely response-based and does not need a linearized system model for eigen-analysis, which makes it applicable to systems whose detailed, complete mathematical models are not available. Considering the unavoidable nonlinearity as exhibited in the transient period of a system response, the Synchrosqueezed Wavelet Transform is applied to simulated responses for modal analysis to obtain participation factors. Based on simulations of Kundur’s two-area system using both the electromagnetic transient model and phasor model, the participation factors estimated by the proposed approach are compared with two other signal processing tools, the Prony analysis and continuous wavelet transform, and are also benchmarked with conventional model-based participation factors.