Volume 15, Issue 6 -

Transmission lines are essential components of electric power grids. Diverse power system applications and simulation based studies require transmission line parameters including series resistance, reactance, and shunt susceptance, and accurate parameters are pivotal in ensuring the accuracy of analyses and reliable system operation. Commercial software packages for performing power system studies usually have their own databases that store the power system model including line parameters. When there is a physical system model change, the corresponding component in the database of the software packages will need to be modified. Manually updating line parameters are tedious and error-prone. This paper proposes a solution for streamlining the calculation of line parameters and updating of their values in respective software databases. The algorithms used for calculating the values of line parameters are described. The software developed for implementing the solution is described, and typical results are presented. The proposed solution is developed for a utility and has a potential to be put into use by other utilities.

To assess and prevent the smart grid information security risks more effectively, this paper provides risk index quantitative calculation method based on absorbing Markov chain to overcome the deficiencies that links between system components were not taken into consideration and studies mostly were limited to static evaluation. The method avoids the shortcomings of traditional Expert Score with significant subjective factors and also considers the links between information system components, which make the risk index system closer to the reality. Then, a smart grid information security risk assessment model on the basis of set pair analysis improved by Markov chain was established. Using the identity, discrepancy, and contradiction of connection degree to dynamically reflect the trend of smart grid information security risk and combining with the Markov chain to calculate connection degree of the next period, the model implemented the smart grid information security risk assessment comprehensively and dynamically. Finally, this paper proves that the established model is scientific, effective, and feasible to dynamically evaluate the smart grid information security risks.

Computer power supplies are required to have multiple isolated regulated dc voltages with low ripple content and high input power factor at the utility interface. A dc–dc converter is used for obtaining these isolated multi-output dc voltages with excellent regulation. In this paper, a non-isolated ac–dc converter is proposed as the first stage converter to obtain a regulated dc output rather than using a simple uncontrolled diode bridge rectifier at the front end. A dc–dc converter is used at the second stage that has a high frequency transformer with multiple secondary windings to obtain different dc voltage levels at the output. The proposed bridgeless converter based power supply is designed using fundamental design equations, and different component values are calculated. Extensive simulations are carried out to demonstrate the improved performance of the proposed bridgeless converter based multi-output computer power supply at varying source voltages and load conditions. Experimental validation of the power supply is carried on a developed hardware prototype, and the test results are compared with the simulated performance for design verification.

The paper’s aim is to explore both active and reactive power losses minimization and voltage stability by a decentralized strategy. The approach assumes that the grid is split into sub-systems; each sub-system is in charge of its own optimal solution using equivalents for the neighbors, so that information exchange is not required. Schedule interchanges among sub-systems have been added as constraints into the optimal formulation. Once the individual solutions are available, the corresponding settings are allocated to the corresponding equipment and a full power flow study is carried out to assure the steady-state preservation. Results are exhibited on two test power systems.

Capacitors and series voltage regulators are used extensively in distribution systems to reduce power losses and improve the voltage profile along the feeders. This paper deals with the problem of contemporaneously choosing optimal locations and sizes for both capacitors and series voltage regulators in three-phase, unbalanced distribution systems. This is a mixed, non-linear, constrained, multi-objective optimization problem that usually is solved in deterministic scenarios. However, distribution systems are stochastic in nature, which can lead to inaccurate deterministic solutions. To take into account the unavoidable uncertainties that affect the input data related to the problem, in this paper, we have formulated and solved the multi-objective optimization problem in probabilistic scenarios. To address the multi-objective optimization problem, algorithms were used in which all the objective functions were combined to form a single function. These algorithms allow us to transform the original multi-objective optimization problem into an equivalent, single-objective, optimization problem, an approach that appeared to be particularly suitable since computational time was an important issue. To further reduce the computational efforts, a linearized form of the equality constraints of the optimization model was used, and a micro-genetic algorithm-based procedure was applied in the solution method.

This paper presents distribution static compensator (DSTATCOM) with dq 0 current controller and sine pulse width modulation (SPWM) switching for compensation of unbalanced nonlinear load in distribution system. DSTATCOM, connected in parallel to load at the point of common coupling (PCC), is used for supplying reactive and harmonic components of load current demand. This dq 0 current controller is implemented in synchronous reference frame (SRF) rotating at fundamental frequency and consists of harmonic compensation (HC) regulator along with proportional integrator (PI) regulator. HC regulator is realized by number of sinusoidal signal integrators (SSIs) in parallel. The SSI provides high gain for tuned harmonic frequency and helps in minimizing filter current tracking error while compensating for load harmonic currents. Zero-axis controller, which compensates load neutral current and helps in obtaining balanced utility currents, is provided along with d , q controllers. SPWM switching generates inverter gating pulses at constant frequency, which reduces stress levels on VSI switches and simplifies the design of interface filter. Simulation studies of DSTATCOM load compensation with dq 0 current controller are carried out in Matlab/Simulink and experimental verification is done using dSpace 1104 with Matlab real-time interface (RTI).

This paper investigates the application of microelectromechanical system (MEMS) switches for DC power distribution system. Traditional electromechanical switches, solid state switches and solid state switch array are studied and simulated to understand their characteristics. Performance and characteristics of MEMS switches are reviewed and identified that electrostatically actuated MEMS switches are suitable for DC power applications. Scalable total cross tied (TCT) array configuration using MEMS switches has been proposed. The proposed configuration is suitable for variable voltage/current rating. Arc-less behavior of the switch configuration is analyzed using modified Paschen’s curve. 400 V/6 A system is considered for the simulation and comparative study. The simulated result of the proposed MEMS switch array configuration is compared with the traditional switches. The comparative study shows that the proposed switch array configuration gives better performance in terms of voltage drop, leakage current, power loss, arc and size. This can be used in DC power system protection, circuit breaking, battery protection and smart grid load switching applications.

Distribution automation (DA) applications are limited to feeder level today and have zero visibility outside of the substation feeder and reaching down to the low-voltage distribution network level. This has become a major obstacle in realizing many automated functions and enhancing existing DA capabilities. Advanced metering infrastructure (AMI) systems are being widely deployed by utilities across the world creating system-wide communications access to every monitoring and service point, which collects data from smart meters and sensors in short time intervals, in response to utility needs. DA and AMI systems convergence provides unique opportunities and capabilities for distribution grid modernization with the DA system acting as a controller and AMI system acting as feedback to DA system, for which DA applications have to understand and use the AMI data selectively and effectively. In this paper, we propose a load segmentation method that helps the DA system to accurately understand and use the AMI data for various automation applications with a suitable case study on power restoration.

In this paper, parameter plane synthesis of a three-phase neutral-point clamped bidirectional rectifier has been performed. The converter involves one outer-loop PI voltage controller and two inner-loop PI current controllers for the closed-loop control. D -partition technique has been employed for the precise design of the voltage controller. An experimental prototype of the converter has been developed, and the experimental investigation of the converter performance in closed loop has been carried out. DSP DS1104 of dSPACE has been used for real-time implementation of the designed controller. The converter gives a very good performance in steady state and dynamic state (for rectification as well as inversion modes of operation) using the designed controller parameters.