This report summarizes several research activities developed by the power faculty and graduate students at Clemson University. Smart grid and renewable energy introduced new subjects to the research program such as: power system modeling and simulation, microgrid, distributed generation, wind power, photovoltaic systems, and application of synchro-phasors in power system operation and control.
Power System Simulation, Protection and Control
Parallel Transient Simulator Based Optimal Control
The goal of this research is to build a parallel transient simulator (par-TS) that is capable of simulating large scale electric grid in faster than real-time. The simulator would enable the real-time adaptive tuning of primary controllers such as power system stabilizer (PSS), governors and excitation systems. Stability and hence security of the grid is enhanced by adaptively tuning the controllers for different operating points.
Water Tree Fault Detection in Underground Cables
Water tree fault is a phenomenon typically associated with aged underground cables. It is characterized by extreme high fault impedance. It is difficult to detect, especially in long cable segments under steady state conditions. In this research the water tree is modelled in COMSOL Multiphysics. Its lumped parameters (resistance and capacitance) are calculated, and then it is integrated in a distribution system to determine how to detect water trees and monitor the health of the feeder.
A Special Protection Scheme Using Synchrophasor Measurements and Sensitivity Analysis
New measurement techniques, primarily phasor measurement units (PMUs) have provided opportunities to improve the power system observability, control and protection. This research includes the formulation and design of a special protection scheme based on a novel utilization of trajectory sensitivity techniques with inputs designed to be provided by PMUs.
A small power system consisting multiple distributed generators (DGs), (Renewable energy sources e.g. Solar, Wind, Diesel Generator etc. ) which can ensure independent operation islanded from bulk power grid and also can be connected to national power grid, is defined as Microgrid. With suitably designed DG control technology consisting power electronics based energy interface, Microgrid can ensure more stable operation of power system with acceptable or high power quality.
The topic of this research is on micro-grid with PV sources. The micro-grid is supposed to be designed for two running modes, which are islanding mode and grid mode. The focus of this research is on the following three points: PV model connected with energy storage devices, testing different running modes with different weather conditions, and effective ways to solve power quality problems in this type of microgrids.
Dynamic Modelling and Stability Analysis of Microgrid
Mathematical model of inverter based distributed energy resources (DERs) are important for quasi-static stability analysis of the microgrid and analyze interaction of controller state variables on the low frequency electromechanical dynamic of the rest of the systems. Modeling research includes model validation, perturbation responses and impact of DERs on system stability using mathematical models as well as EMTP software.
Plug-In Electric Vehicle
Single Phase Plug-In Electric Vehicle Chargers
For the purpose of this research, two types of Plug-In Electric Vehicle (PEV) chargers are implemented. Each of them has an AC/DC and a DC/DC converter stage. Both types of chargers have the same topology and differ only in their control methodologies for the AC/DC stage. The actual current flowing into the charger is compared with the reference to generate the required gating signals for the AC/DC stage.
Fault Analysis on an Unbalanced Distribution System in the Presence of PEVs
Increasing penetration of PEVs may lead to unexpected impacts on distribution power systems. This research investigates the impacts on faults in a distribution system with the addition of PEVs. The focus is to examine the impact of a smart car park during faults in an unbalanced distribution system. It is desired to mitigate the negative impacts observed with some of the PEV chargers in order to protect the system.
The large scale integration of renewable energy sources has resulted in intermittency and complex power flows in the system. Wind energy has been one of the popular renewable sources connected to the grid. With integration levels reaching several hundred megawatts, their impact on power system stability has to be studied, which includes building the dynamic model of a Doubly fed induction generator (DFIG), studying the small signal stability or the impact of large scale integration on the eigenvalues of the system.
Series Compensated Lines
The focus of this research is analysis of faulted power systems with MOV-Protected series capacitors with renewable integration using phase coordinate approach.
This research concentrates on contingency analysis of power system with large scale integration of renewable energy sources. With increased levels of renewable energy generation, the contingency set must be augmented to include those extreme ramp events which are due to renewable energy and outages of renewable energy power plants.
Photovoltaic (PV) System
As the need for renewable is increasing, high PV penetration level is expected. Grid control and operation become more difficult as the level of PV increases; these difficulties can result in system failure. This research focus is to address the impact of large scale PV penetration on the transmission system.
Energy Storage Systems and Market Model
There is a variety of Energy Storage Systems (ESS). Each one has its own advantages, disadvantages and special features. Studying and analyzing the systems behavior can lead to the suitable choice for a given application. This study focused on Battery Energy Storage Systems (BESS). The financial impact of a BESS was studied. Upon obtaining the total cost of the BESS and given the profit from the operation of the system we can calculate the financial impact of the ESS on the grid.