Deepak Pullaguram

Non-linear fractional order controllers for autonomous microgrid system

This paper describes a design of a non-linear fractional order PID controller for voltage source inverters (VSI) in autonomous microgrid system. The gains of the fractional order controllers are tuned using particle swarm optimization technique (PSO). The performance of the tuned controllers is tested for different perturbations like switching of inductive loads, switching of non linear loads and single line to ground faults. The paper encompasses a comparative study of the performance of the conventional PI controllers and the non linear fractional order controllers for autonomous microgrid system. Simulation results clearly indicate the improvement in the performance of the microgrid due to the use of fractional order PID (FOPID) controllers.

Coordinated single-phase control scheme for voltage unbalance reduction in low voltage network

Low voltage (LV) distribution systems are typically unbalanced in nature due to unbalanced loading and unsymmetrical line configuration. This situation is further aggravated by single-phase power injections. A coordinated control scheme is proposed for single-phase sources, to reduce voltage unbalance. A consensus-based coordination is achieved using a multi-agent system, where each agent estimates the averaged global voltage and current magnitudes of individual phases in the LV network. These estimated values are used to modify the reference power of individual single-phase sources, to ensure system-wide balanced voltages and proper power sharing among sources connected to the same phase. Further, the high X/R ratio of the filter, used in the inverter of the single-phase source, enables control of reactive power, to minimize voltage unbalance locally. The proposed scheme is validated by simulating a LV distribution network with multiple single-phase sources subjected to various perturbations. This article is part of the themed issue ‘Energy management: flexibility, risk and optimization’.

Dynamic droop based inverter control for autonomous microgrid

Developments in the renewable generation along with the power electronic converters gave huge scope of research in microgrid through which there can be little chance of meeting the load demand. Integration of microgrids into the existing system leads to lots of changes in the power system. So detail analysis is required for the microgrid level to achieve better performance in the existing system. In this paper the systematic small signal modeling of an islanded AC microgrid operating under various kinds of loading conditions is discussed. From the small-signal dynamic analysis of the microgrid, it can be observed as the loading condition changes, the low-frequency modes of the power sharing dynamics drifts to new locations and the damping of the system varies according to the real power load which affects relative stability of the system, and eventually may lead to instability. To avoid this instability a dynamic droop settings is proposed in this work which modifies its droop in accord to the inverter output current.

Standalone BLDC based solar air cooler with MPPT tracking for improved efficiency

This paper proposes the idea of using Solar Energy as a source of power for designing and developing standalone air cooling system with longer life, less maintenance and better performance, particularly useful for rural areas that have a considerable amount of solar radiation and have no access to grid systems. This system comprises of a photovoltaic (PV) array along with DC-DC boost converter that ensures maximum power point (MPP) operation. Two Permanent Magnet Brushless Direct Current (BLDC) motors are employed to drive a centrifugal water pump and an air blower coupled to their individual shafts. The proposed air cooling system is designed to obtain satisfactory system performance even under dynamic conditions. Suitability of the proposed system for various perturbations is evaluated by simulating the proposed system using MATLAB/Simulink.

A consensus priority algorithm based V2G charging framework for frequency response

This paper presents a novel consensus priority algorithm based V2G charging framework to combat fluctuating loads as well as generation shortage on a large scale consequently resulting into frequency deviation. A consumer input database has been maintained whilst charging so that frequency response is coordinated from the plug-in electric vehicles as per the battery longevity requirements within a participating V2G range for various state-of-charge (SoC) levels. To ensure battery longevity, an adaptive droop based charge seizing control scheme has also been implemented. It has been implemented in MATLAB/SIMULINK under various scenarios to demonstrate the effectiveness of the control algorithm. Furthermore, it has been validated experimentally in a 1 kVA setup.

Lyapunov based frequency independent current controller for grid connected single phase PV systems

This paper proposes a control scheme for single phase inverter based systems. The inverter controller consists of two loops; the inner current control loop which is the faster one while the outer voltage / active and reactive power control loop is the slower one. A Lyapunov based inner (current) control is presented in this work which robustly tracks the reference current independent of the system frequency. The proposed controller is used in a grid connected single phase Photo Voltaic (PV) system and is compared with a Proportional Resonant (PR) and sliding mode controller which are generally used in AC systems. While the PR controller is tuned to operate at a particular frequency, the proposed controller performs much better in terms of tracking the reference current at any frequency. The controller is derived using the system differential equation and obtaining asymptotical stability using Lyapunovs stability criteria.