The coexistence of ac and dc subgrids in a hybrid microgrid is likely given that modern distributed sources can either be ac or dc. Linking these subgrids is a power converter, whose topology should preferably be not too unconventional. This is to avoid unnecessary compromises to reliability, simplicity, and industry relevance of the converter. The desired operating features of the hybrid microgrid can then be added through this interlinking converter. To demonstrate, an appropriate control scheme is now developed for controlling the interlinking converter. The objective is to keep the hybrid microgrid in autonomous operation with active power proportionally shared among its distributed sources. Power sharing here should depend only on the source ratings and not their placements within the hybrid microgrid. The proposed scheme can also be extended to include energy storage within the interlinking converter, as already proven in simulation and experiment. These findings have not been previously discussed in the literature, where existing schemes are mostly for an ac or a dc microgrid, but not both in coexistence.

Autonomous Control of Interlinking Converters with Energy Storages in Hybrid AC-DC Microgrids

Flexible AC transmission systems, so-called FACTS devices, can help reduce power flow on overloaded lines, which would result in an increased loadability of the power system, fewer transmission line losses, improved stability and security and, ultimately, a more energy-efficient transmission system. In order to find suitable FACTS locations more easily and with more flexibility, this paper presents a graphical user interface (GUI) based on a genetic algorithm (GA) which is shown able to find the optimal locations and sizing parameters of multi-type FACTS devices in large power systems. This user-friendly tool, called the FACTS Placement Toolbox, allows the user to pick a power system network, determine the GA settings and select the number and types of FACTS devices to be allocated in the network. The GA-based optimization process is then applied to obtain optimal locations and ratings of the selected FACTS to maximize the system static loadability. Five different FACTS devices are implemented: SVC, TCSC, TCVR, TCPST and UPFC. The simulation results on IEEE test networks with up to 300 buses show that the FACTS placement toolbox is effective and flexible enough for analyzing a large number of scenarios with mixed types of FACTS to be optimally sited at multiple locations simultaneously.

Optimal placement of multiple-type FACTS devices to maximize power system loadability using a generic graphical user interface

Optimal location and control of a unified power flow controller (UPFC) along with transformer taps are tuned with a view to simultaneously optimize the real power losses and voltage stability limit (VSL) of a mesh power network. This issue is formulated as a nonlinear equality and inequality constrained optimization problem with an objective function incorporating both the real power loss and VSL. A new evolutionary algorithm known as bacteria foraging is applied for solving the multiobjective multivariable problem, with the UPFC location, its series injected voltage, and the transformer tap positions as the variables. For a single objective of only real power loss, the same problem is also solved with interior point successive linearization program (IPSLP) technique using the LINPROG command of MATLAB. A comparison between the two suggests the superiority of the proposed algorithm. A cost effectiveness analysis of UPFC installation vis-agrave-vis loss reduction is carried out to establish the benefit of investment in a UPFC

Bacteria Foraging-Based Solution to Optimize Both Real Power Loss and Voltage Stability Limit

Optimal location and sizing of DSTATCOM in distribution systems by immune algorithm

Congestion management in power systems – A review

Application of particle swarm optimization technique for optimal location of FACTS devices considering cost of installation and system loadability

This paper presents the application of particle swarm optimization (PSO) technique to find optimal location of flexible AC transmission system (FACTS) devices to achieve maximum system loadability with minimum cost of installation of FACTS devices While finding the optimal location, thermal limit for the lines and voltage limit for the buses are taken as constraints Three types of FACTS devices, thyristor controlled series compensator (TCSC), static VAr compensator (SVC), and unified power flow controller (UPFC) are considered The optimizations are performed on four parameters namely the location of FACTS devices, their setting, their type, and installation cost of FACTS devices Two cases namely, single type devices (same type of FACTS devices) and multi type devices (combination of TCSC, SVC, and UPFC) are considered Simulations are performed on IEEE 6 and 30 bus systems for optimal location of FACTS devices and the results obtained are encouraging and will be useful in electrical restructuring

Application of PSO technique for optimal location of FACTS devices considering system loadability and cost of installation

In the present work, stir casting route is used to fabricate the duplex (α–β) brass plate. The machineabilty behavior of the (α–β) brass is analyzed during Electrical Discharge Machining (EDM) using Taguchi method. Experiments were conducted with three machining variables such as current, pulse-on time and voltage. Material removal rates (MRR), Electrode wear rate (EWR) and surface roughness (SR) are chosen as the output parameters. Results of SN ratio analysis showed that peak current was significant factor to affect the all the responses. Analysis of variance (ANOVA) was used to identify the contribution of each parameter.

Parametric optimization of EDM process on α–β brass using Taguchi approach

Multilevel inverters have been widely used for high-voltage and high-power applications. Their performance is greatly superior to that of conventional two-level inverters due to their reduced total harmonic distortion (THD), lower switch ratings, lower electromagnetic interference, and higher dc link voltages. However, they have some disadvantages such as an increased number of components, a complex pulse width modulation control method, and a voltage-balancing problem. In this paper, a novel nine-level reduced switch cascaded multilevel inverter based on a multilevel DC link (MLDCL) inverter topology with reduced switching components is proposed to improve the multilevel inverter performance by compensating the above mentioned disadvantages. This topology requires fewer components when compared to diode clamped, flying capacitor and cascaded inverters and it requires fewer carrier signals and gate drives. Therefore, the overall cost and circuit complexity are greatly reduced. This paper presents modulation methods by a novel reference and multicarrier based PWM schemes for reduced switch cascaded multilevel inverters (RSCMLI). It also compares the performance of the proposed scheme with that of conventional cascaded multilevel inverters (CCMLI). Simulation results from MATLAB/SIMULINK are presented to verify the performance of the nine-level RSCMLI. Finally, a prototype of the nine-level RSCMLI topology is built and tested to show the performance of the inverter through experimental results.

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Performance Analysis of a Novel Reduced Switch Cascaded Multilevel Inverter

This paper describes the application of particle swarm optimization (PSO) technique to find the optimal setting of thyristor-controlled series capacitors (TCSCs) in order to eliminate or minimize line overloads under single contingency or critical double contingency and to minimize the installation cost of TCSCs. The proposed approach uses Contingency Sensitivity Index (CSI) to rank the system branches according to their suitability for installing a TCSC. Once the locations are determined, PSO technique is used to find the best settings for the installed TCSCs to eliminate or minimize the line overloads in case of all the possible single contingencies or critical double contingencies and to minimize the installation cost of TCSCs. The voltage magnitude at each bus and the line flow through each branch for all the buses and branches respectively, have been considered as inequality and equality constraints. The proposed approach enhances the static security of the power system with minimum installation cost of TCSC. The IEEE 6-bus and 30-bus systems are used to validate the proposed approach

M. Saravanan

Papers

Application of particle swarm optimization technique for optimal location of FACTS devices considering cost of installation and system loadability

Application of PSO technique for optimal location of FACTS devices considering system loadability and cost of installation

Parametric optimization of EDM process on α–β brass using Taguchi approach

Performance Analysis of a Novel Reduced Switch Cascaded Multilevel Inverter

Application of PSO technique to find optimal settings of TCSC for static security enhancement considering installation cost