Dharmendra Kumar Dheer

Transient analysis of an inverter based source operating in microgrids

Traditional microgrids have sources whose transient response is limited by process or mechanical time constants depending on the technology used. Inverter based sources provide the flexibility in designing and tuning the controller parameters so as to operate microgrid within specified constraint in voltage and frequency. For this it is imperative to investigate the effect of controller parameters and different operating conditions on inverter response and define the response in terms of standard transient parameters such as damping, natural frequency and inertia. In this work a methodology has been defined to model the inverter based source as voltage magnitude and phase transfer function. Effect of controller and filter parameters as well as different operating conditions on low, medium and high frequency inverter transients is then obtained and analyzed. Simulation of an inverter based source, is done using Simulink/MATLAB software to validate the analysis.

Small signal stability in microgrids with high penetration of power electronics interfaced sources

In this paper, effect of power electronics interfaced sources on small signal stability in the presence conventional sources (synchronous generators) in a microgrid is studied. A detailed mathematical model for small signal analysis is presented. The models are linearised around operating point and state space matrix is used to find the eigenvalues at that point. Eigen value analysis is done to study the effect of placement of inverter and/or synchronous generator in a system on its stability. The effect of droop system response is also studied. Steady state stability of microgrid with different combinations of inverters and synchronous generators is presented and maximum allowable droop gain and damping factor for these cases is determined. From the analysis it is found that inverters at some locations tend to make system critical. It is also found that replacing these inverters with synchronous generators increase the stability margin. The results is validated by simulation (eigen value analysis) in MATLAB.

Small signal modeling and stability analysis of a droop based hybrid AC/DC microgrid

This paper presents dynamic model and stability analysis of droop based AC/DC Hybrid microgrid. The power electronic interface on ac side of the microgrid consist of voltage source inverters and the dc side constitute of dc/dc converters. The developed model is linearised at an operating point to investigate the stability analysis of this hybrid system. Effect of stability margin with droop gain is investigated in detail using eigenvalue analysis. This analysis is subsequently verified through time domain simulation in MATLAB/SIMULINK.

Stability and fault analysis of a hybrid AC/DC fighter Aircraft

The aerospace industry is growing rapidly with the technological advancement in the field. The aircraft equipped with legacy technology is known as conventional aircraft, moving towards More Electric Aircraft (MEA) and All Electric Aircraft (AEA). In the present scenario AEA is more popular among the aircraft manufacturers and undergoing advanced developments on technological platform. In his research, study has been stared with conventional aircraft and i is extended to the proposed aircraft in which rotary inverter and silver zinc battery have been replaced by static inverter and lithium ion battery respectively. Advantage of static inverter over rotary inverter and lithium ion battery over silver zinc battery have been discussed in detail. Fault analysis has been carried out to compare the transient behaviour of proposed aircraft with respect to the conventional aircraft in time domain simulation in MATLAB. Dynamic model of aircraft has been obtained to investigate the stability study using eigenvalue analysis.

Effect of reconfiguration and mesh on small signal stability margin of a droop-based islanded microgrid

This paper investigates the effect of reconfiguration and network type (mesh/radial) on small signal stability margin of a droop-based islanded microgrid. A low voltage microgrid and standard IEEE 33 bus system (with three and five sources) are considered for study. From eigenvalue analysis and root locus plot, it is found that the reconfiguration and network type has significant effect on small signal stability. Results are verified through time domain simulation using MATLAB/SIMULINK for the systems considered.