M. Venkata Kirthiga

Computational Techniques for Autonomous Microgrid Load Flow Analysis

This paper attempts at developing simple, efficient, and fast converging load flow analysis techniques tailored to autonomous microgrids. Two modified backward forward sweep techniques have been developed in this work where the largest generator is chosen as slack generator, in the first method and all generator buses are modeled as slack buses in the second method. The second method incorporates the concept of distributed slack bus to update the real and reactive power generations in the microgrid. This paper has details on the development of these two methodologies and the efficacy of these methods is compared with the conventional Newton Raphson load flow method. The standard 33-bus distribution system has been transformed into an autonomous microgrid and used for evaluation of the proposed load flow methodologies. Matlab coding has been developed for validating the results.

Optimal sizing of hybrid generators for autonomous operation of a micro-grid

As a matter of fact, there is an ever increasing need for augmenting renewable resources to the existing power system in order to meet its increasing demand. These resources are generally connected to the distribution network, thereby alleviating the stress on the network and also providing the necessary reliability. A distribution network with renewable and fossil-based resources is a micro-grid. Such a micro-grid may be operated either in Autonomous (isolated from the utility grid) or Non-Autonomous (connected to the grid) mode of operation. This paper attempts to develop an algorithm to determine the sizes of the renewable resources for autonomous operation of the micro-grid using Particle Swarm Optimization and Modified Genetic Algorithm based optimization techniques. MATLAB code has been developed and sizing of generators for a standard 33 bus distribution system has been presented to demonstrate the utility of the methodology.

Optimal siting & sizing of distributed generators in micro-grids

In view of bridging the gap between increasing power demand and limited generation, augmentation of renewable resources into existing power systems is gaining importance. Distribution network which includes these small generating sources and loads are called micro-grids which can work either in non-autonomous or autonomous mode. In this regard, this paper attempts at determining the optimal location for placing the Distributed Generators based on Loss Sensitivity Factor and also proposes Successive sizing based algorithm for determining their optimal sizes, both in autonomous and non-autonomous microgrids. The results obtained by the proposed algorithm are compared with that obtained by implementing Particle Swarm Optimization for the same. MATLAB coding has been developed and the standard 33 bus radial distribution system has been transformed to micro-grid to verify the proposed methodology.

Investigations on a Modern Self-Defined Extinction Advance Angle Controller for HVDC Systems

This paper proposes a modern self-defined extinction advance angle controller and also investigates in detail its performance analysis under different operating conditions. The self-defined controller suggests a new method of measuring extinction advance angle a which helps to maintain the preferred value of a constant. The proposed controller is dedicated for the inverter end converter and hence the rectifier end converter is provided with the standard CIGRE controller. The performance of the proposed controller has been investigated under different operating conditions including post fault recovery capability and compared with the standard CIGRE controller. Also a fault mitigation technique has been attempted for a link to ground fault and the robustness of the controller has been investigated along with the fault mitigation technique. It has been found that the proposed controller has an outstanding performance particularly at post fault operating conditions. PSCAD/EMTDC simulation software has been utilized for the investigations of the proposed controller and the standard CIGRE benchmark system has been used for analysis in this paper.

Investigations on modern self-defined controller for hybrid HVDC systems

This paper proposes a modern self-defined extinction advance angle controller and investigates its suitability for Hybrid HVDC systems. The self-defined controller suggests a new method of measuring extinction advance angle γ which helps to maintain the preferred value. The proposed controller is dedicated for the receiving end converter operated in inverter mode and hence a Hybrid HVDC system with VSC at the rectifier and LCC at the inverter have been adopted in this paper. The performance of the proposed controller has been investigated under different operating conditions including post fault recovery. Also a fault mitigation technique has been attempted for a link to ground fault and the robustness of the controller has been confirmed in conjunction with the fault mitigation technique. PSCAD/EMTDC simulation software has been used for validating the proposed controller and the standard CIGRE benchmark system has been used for evaluating the proposed controller in this paper.

Adaptive re-configuration and islanding of micro-grids based on frequency deviations

Adaptive re-configuration and islanding of micro-grids, based on the frequency deviations are attempted in this paper. The proposed technique improves the reliability of autonomous micro-grid under contingencies through adaptive control. Also concept of domains and commons of the distributed generators present in the micro-grids have been used in the proposed methodology. This algorithm is found to be effective for autonomous micro-grids under various operating conditions and also verifies the stability of the islanded portions. The algorithm has been validated for the standard 33 bus distribution system in this paper.

Stability analysis of islanded micro-grids

Islanding of micro-grids is inevitable to improve the reliability of the system and hence this paper proposes a new methodology for adaptive re-configuration and islanding of micro-grids based on the knowledge of domains and commons of the distributed generators (DGs). The DGs are modeled with Automatic Generation Control (AGC) and Automatic Voltage Regulator (AVR) loop so as to regulate the frequency and voltage of the system during disturbances. The stability of the system has been analyzed while adopting the proposed islanding method by considering different contingency cases. The efficacy of the proposed method is verified by performing case studies on the standard 33 bus distribution system transformed into an autonomous micro-grid.

Noval topology for reliable PMSG based wind Energy Conversion system

A robust and reliable wind power evacuation scheme through a Permanent-Magnet Synchronous Generator (PMSG) is proposed in this paper. In this topology, a generatorside passive bridge rectifier and a grid-side Buck Boost Inverter (BBI) is employed to facilitate an efficient and economical Wind Energy Conversion system. In BBI, the peak value of the alternating output voltage is independent on the direct input voltage and also filters are not needed since a pure sinusoidal output voltage is obtained. The Double Loop Control Strategy (DLCS) is implemented for the BBI, as it incorporates two feed-forward loops intended to increase the robustness of the inverter to external disturbances and fluctuations in voltage due to wind velocity variations. The primary merit of the proposed configuration is that it does not require active front-end converter. The performance and significance of the proposed topology has been verified by PSCAD simulations.

A case study for controlled islanding based on line contingency ranking in autonomous micro-grids

Micro-grids are formed on introduction of Distributed Generator(DG) units in conventional distribution systems. These micro-grids operate in either autonomous mode or non-autonomous mode. When line contingencies occur in micro-grids, there are chances for formation of accidental islands. This paper proposes an algorithm for forming controlled islands on occurrence of line contingencies in micro-grids, using the information about accidentally formed islands and line contingency ranking. Identification of such accidental islands has been attempted in this work, by tracing the change in the configuration of the autonomous micro-grids. Ranking of line contingencies is done with the database of the detected accidental islands. The proposed algorithm is also attempted for radial and weakly meshed structures based on the voltage profile, performance indices, line losses and transient stability of the DGs. MATLAB coding is developed to validate the proposed algorithm & the standard 33-node radial distribution system is used for validation of the proposed algorithm.

A modern self-defined extinction advance angle controller for CCC based Hybrid HVDC systems

HVDC systems are attractive alternatives to increase the transmittable power. Hybrid HVDC systems are being suggested in particular for wind power evacuation applications. This paper recommends the modern self-defined extinction advance angle controller for Hybrid HVDC systems and also investigates its suitability under various operating conditions. The proposed controller employs a simple device level measurement of extinction advance angle (γ). A Hybrid HVDC system with Voltage Source Converter (VSC) at the rectifier and Capacitor Commutated Converter (CCC) at the inverter end is adopted for analysis in this paper. The proposed controller is dedicated to the receiving end converter operated in inverter mode and the sending end converter operated in rectifier mode is supplemented with the standard CIGRE controller. The performance of the proposed controller has been investigated under different operating conditions including post fault recovery. Also a fault mitigation technique is attempted for a DC link to ground fault and the robustness of the controller has been validated. PSCAD/EMTDC simulation software has been used.