Srikanthan Sridharan

This paper analyzes the low-frequency stability challenges that exist in a complex DC microgrid (MG) system. The converters that belong to a DC MG are categorized into different groups based on their control approach. The small-signal model of the DC MG is presented, and the conditions for system stability are derived. In some DC MG applications, there is the possibility of installing off-the-shelf converters with little flexibility and access for controller auto-tuning. To tackle this, a hardware-based active voltage stabilizer solution is proposed to stabilize the DC MG. The active stabilizer's functionality, based on an isolated bidirectional DC-DC converter, is elucidated, and a suitable control strategy is proposed. The active stabilizer and its associated control configuration involve only local voltage sensing and are non-intrusive. A dual active bridge (DAB) converter-based active stabilizer is implemented, and hardware-based steady-state and transient experimental results from a DC MG test-bench are provided to validate the functionality and effectiveness of the proposed active stabilizer.

A novel current control strategy for a three-phase three-leg distribution static compensator is propounded in this paper. Improvement is achieved in terms of constancy and reduction in switching frequencies of all the switches of the voltage source inverter. The switching commands for one of the three inverter legs are given directly from a square pulse of a user-defined frequency. The other two legs are operated in hysteresis current tracking mode. The proposed controller unlike the other controllers allows the user to directly set the switching frequency of all the inverter switches and is devoid of any transformation, modulation, look-up table or complexity to achieve the objectives. The proposed scheme is validated through extensive simulation results in a three-phase three-wire distribution system with non-linear unbalanced load. © 2008 IEEE.

The need for vehicle electrification is growing across the world. However, increased cost and packaging volume considerations arising out of electrification, pose a major barrier to the adoption of electrified vehicles. One of the ways to alleviate cost and packaging volume concerns is through appropriate rating and sizing of the electric powertrain, which is influenced by several factors including power flow magnitude, energy storage capability, thermal limits, voltage and current limits, and packaging requirements. This paper presents practical powerflow considerations in the electric powertrain, associated challenges and potential directions towards reducing the cost and packaging volume of the e-drive system. The target vehicle segment considered for electrification in this study are twowheeled and three-wheeled road vehicles, which are dominant segments of India's vehicle population. Electrification of this segment is expected to result in significant benefits, both for market penetration as well as the environment. The vehicle considered in the study consists of an e-drive system using a 48 V battery pack, connected to a three-phase power electronic inverter supplying a single electric machine for traction. Limits on e-drive system efficiency under these practical conditions for a range of torque-speed operating points are also discussed.