Kai Sun 孙凯

Reserach Highlights

This page lists and categorizes major research results of journal publications.

Understanding and Control of Power System Oscillations

The traditional classification and methods on power system stability that has been practiced for decades will no longer be adequate to real-life dynamics and instability events in power grids with high penetration of renewable distributed energy resources (DERs). Our goal is to acquire an in-depth understanding in nonlinear modal dynamics of a power grid as a nonlinear multi-oscillator system and establish a new methodology named Nonlinear Modal Decoupling for improving power system stability by wide-area measurements and coordination control of DERs.

• Forced, Subsynchronous or Nonlinear Power System Oscillations
  
  - Location and Mechanism Analysis of Oscillation Source in Power Plant (IEEE ACCESS '20)
  - Understanding a Type of Forced Oscillation Caused by Steam-turbine Governors (IEEE TEC '20)
  - Characterization of Subsynchronous Oscillation with Wind Farms Using Describing Function and Generalized Nyquist Criterion (IEEE TPWRS '20)
  - Understanding Subsynchronous Oscillations in DFIG-based Wind Farms without Series Compensation (IEEE ACCESS '19)
  - Location Methods of Oscillation Sources in Power Systems: A Survey (MPCE '17)
  - Second-order oscillation mode study of hydropower system based on linear elastic model and modal series method (ITEES '17)
  - Properties of the Frequency-Amplitude Curve (IEEE TPWRS '17)
  - Formulation and Characterization of Power System Electromechanical Oscillations (IEEE TPWRS '16)
  - A Phase Locked Loop-based Approach to Real-time Modal Analysis on Synchrophasor Measurements (IEEE TSG '14)
  
  
• Nonlinear Modal Decoupling
  
  - Nonlinear Modal Decoupling Based Power System Transient Stability Analysis (IEEE TPWRS '19)
  - Nonlinear Modal Decoupling of Multi-Oscillator Systems with Applications to Power Systems (IEEE ACCESS '18)
  
  
• Oscillation Damping Control
  
  -Real-time Damping Estimation on Nonlinear Electromechanical Oscillation (IEEE TPWRS '21)
  -A Hybrid Energy and Mode Decomposition-based Method for Evaluating Generators Damping in Multi-Machine Power Systems (IEEE Access '21) - Optimization of Battery Energy Storage to Improve Power System Oscillation Damping (IEEE TSTE'19)
  - Damping Control for a Target Oscillation Mode Using Battery Energy Storage (MPCE '18)
  - Design and Implementation of a Measurement-based Adaptive Wide-Area Damping Controller Considering Time Delays (EPSR '16)
  
  

Faster-Than-Real-Time Power System Simulation

Real-time simulation is crutial to ensure power grid resilience against major disturbances. However, there is not much room for traditional numerical simulation to improve time performance. Leveraged by high-performance supercomputers, we are estabilising a new, semi-analytical approach for faster power system simulation in deterministic and stochastic manners to address increasing uncertainties in grid operations brought by renewables.

• Semi-Analytical Approaches
  
  - Contingency Analysis Based on Partitioned and Parallel Holomorphic Embedding (IEEE TPWRS '21)
  - A Semi-Analytical Solution Approach for Solving Constant-Coefficient First-Order Partial Differential Equations (IEEE L-CSS '21)
  - Examination of Semi-Analytical Solution Methods in the Coarse Operator of Parareal Algorithm for Power System Simulation (IEEE TPWRS '21)
  - A Dynamized Power Flow Method based on Differential Transformation (IEEE Access '20)
  - Solving Power System Differential Algebraic Equations Using Differential Transformation (IEEE TPWRS '19)
  - Efficient and Robust Dynamic Simulation of Power Systems with Holomorphic Embedding (IEEE TPWRS '19)
  - Vectorized Efficient Computation of Pade Approximation for Semi-Analytical Simulation of Large-Scale Power Systems (IEEE TPWRS '19)
  - Power System Time Domain Simulation Using a Differential Transformation Method (IEEE TPWRS '19)
  - Voltage Stability Analysis of Power Systems with Induction Motors Based on Holomorphic Embedding (IEEE TPWRS '19)
  - A Time-Power Series Based Semi-Analytical Approach for Power System Simulation (IEEE TPWRS '19)
  - Fast Power System Dynamic Simulation Using Continued Fractions (IEEE ACCESS '18)
  - Power System Simulation Using the Multistage Adomian Decomposition Method (IEEE TPWRS '17)
  
  
• Nonlinear Model Reduction
  
  - Adaptive Nonlinear Model Reduction for Fast Power System Simulation (IEEE TPWRS '18)
  
  

Cascading Failures

These efforts develop new models, simulation tools and control strategies to understand, prevent and mitigate cascading failures in interconnected power grids.

• Simulation of Cascading Failures
  
  - Towards Simulation and Risk Assessment of Weather-Related Outages (IEEE TSG '18)
  - Simulation of Cascading Outages Using a Power Flow Model Considering Frequency (IEEE ACCESS '18)
  - Efficient Simulation of Temperature Evolution of Overhead Transmission Lines Based on Analytical Solution and NWP (IEEE TPWRD '18)
  - A Multi-timescale Quasi-Dynamic Model for Simulation of Cascading Outages (IEEE TPWRS '16)
  
  
• Modeling of Cascading Failures
  
  - An Online Search Method for Representative Risky Fault Chains Based on Reinforcement Learning and Knowledge Transfer (IEEE TPWRS '20)
  - Mitigation of Cascading Outages Using a Dynamic Interaction Graph-Based Optimal Power Flow Model (IEEE ACCESS '19)
  - Efficient Estimation of Component Interactions for Cascading Failure Analysis by EM Algorithm (IEEE TPWRS '18)
  - Multi-Layer Interaction Graph for Analysis and Mitigation of Cascading Outages (IEEE JETCAS '17)
  - An Interaction Model for Simulation and Mitigation of Cascading Failures (IEEE TPWRS '15)
  - Management of Cascading Outage Risk Based on Risk Gradient and Markovian Tree Search (IEEE TPWRS '17)
  - Risk Assessment of Multi-timescale Cascading Outages based on Markovian Tree Search (IEEE TPWRS '16)
  - Estimating the Propagation of Interdependent Cascading Outages with Multi-Type Branching Processes (IEEE TPWRS '17)
  
  
• System Islanding and Restoration
  
  - Identifying the Timing of Controlled Islanding Using a Controlling UEP Based Method (IEEE TPWRS ' 18)
  - Real-Time Optimized Load Recovery Considering Frequency Constraints (IEEE TPWRS '19)
  - An advanced power system partitioning method for fast and reliable restoration: towards a self-healing power grid (IET-GTD '18)
  - Mixed-Integer Linear Programming-Based Splitting Strategies for Power System Islanding Operation Considering Network Connectivity (IEEE SJ '18)
  - Mixed Integer Second Order Cone Relaxation With Dynamic Simulation for Proper Power System Islanding Operations (IEEE JETCAS '17)
  
  

Voltage Stability and Control

A major concern in grid operations is voltage instability, which will become more critical with the increasing penetration of intermittent DERs. Our research in this field develops new methods to improve online voltage stability assessment (VSA) and VAR control.

• Holomorphic Embedding Methods
  
  - Remote Voltage Control Using the Holomorphic Embedding Load Flow Method (IEEE TSG '19)
  - Voltage Stability Analysis of Power Systems with Induction Motors Based on Holomorphic Embedding (IEEE TPWRS '18)
  - Probabilistic Power Flow Analysis Using Multi-Dimensional Holomorphic Embedding and Generalized Cumulants (IEEE TPWRS '18)
  - Multi-Stage Holomorphic Embedding Method for Calculating the Power-Voltage Curve (IEEE TPWRS '18)
  - A Multi-Dimensional Holomorphic Embedding Method to Solve AC Power Flows (IEEE ACCESS '17)
  - Online Voltage Stability Assessment for Load Areas Based on the Holomorphic Embedding Method (IEEE TPWRS '17)
  
  
• Measurement-based Methods
  
  - Measurement-Based Voltage Stability Assessment Considering Generator VAR Limits (IEEE TSG '19)
  - Measurement-based Voltage Stability Assessment for Load Areas Addressing n-1 Contingencies (IET-GTD '17)
  - Measurement-Based Real-Time Voltage Stability Monitoring for Load Areas (IEEE TPWRS '16)
  
  
• Reactive Power Management and Control
  
  - Optimization of SVC settings to improve post-fault voltage recovery and angular stability (MPCE '18)
  - Optimal Allocation of Dynamic Var Sources Using the Voronoi Diagram Method Integrating Linear Programing (IEEE TPWRS '17)
  - Optimal Placement of Dynamic Var Sources by Using Empirical Controllability Covariance (IEEE TPWRS '17)
  
  

Other Topics

• Dynamic State Estimation
  
  - Dynamic State Estimation for Multi-Machine Power System by Unscented Kalman Filter with Enhanced Numerical Stability (IEEE TSG '18)
  - Power System Observability and Dynamic State Estimation for Stability Monitoring Using Synchrophasor Measurements (CEP '16)
  - Optimal PMU Placement for Power System Dynamic State Estimation by Using Empirical Observability Gramian (IEEE TPWRS '15)
  
  
• Microgrid
  
  - Optimized Autonomous Operation Control to Maintain the Frequency, Voltage and Accurate Power Sharing for DGs in Islanded Systems (IEEE TSG '20)
  - Optimal Distributed Generator Placement in Utility-Based Microgrids during a Large-Scale Grid Disturbance (IEEE ACCESS '20)