Suresh Vadhva

A simple and effective approach for peak load shaving using Battery Storage Systems

This paper discusses a simple method to perform peak load shaving through the means of energy storage systems owned by a utility. Peak load shaving, also referred to as load leveling or peak shifting, consists of the schemes used to eliminate the peaks and valleys in the load profile. This practice offers direct and indirect benefits to utilities in generation costs, line loss reduction, and volt support. Prior work in peak load shaving has been mainly focused on optimization approaches implemented through methods such as non-linear and dynamic programming, or heuristic approaches such as particle-swarm optimization. The proposed algorithm for peak load shaving in this paper is based on a simple approach which compares the aggregated load profile with its average in a certain utilization period and shares the charge/discharge amongst energy storage devices based on the definition of energy bars and weighting factors. In particular, the paper focuses on the usage of Battery Energy Storage Systems (BESS) to accomplish this task. Results show that the proposed algorithm offers a simple, fast and effective way for peak-load shaving without heavy computational burdens often needed in other methods. As a result, it can be easily implemented in a utility main substation for controlling the charge/discharge of storage devices throughout the distribution system.

Smart grid, Distributed Generation, and standards

The purpose of this paper is to gather and document the most pertinent information about the “Smart Grid, ” explore its many components, and propose some suitable attributes while considering Distributed Generation (DG) interconnection as a major integral part. Effects of various Smart Grid components on Generation, Transmission, Substation and other sections of the power systems are identified and discussed. Latest DG interconnection rules and standards are reviewed and presented. Major technical concerns due to interconnection of DG at higher penetrations are investigated and explored by simulations using a utility grade computer program. Simulation results verifying the technical issues are presented. Some of the main limitations of the current rules and standards are pointed out. Some solutions and further research to overcome these limitations are proposed.

Distributed generation issues, and standards

The purpose of this paper is to investigate Distributed Generation (DG) standards and interconnection issues at higher penetration levels. A clear concise definition of “Smart Grid” is presented to illustrate the importance of distributed generation along with the other important aspects of the Smart Grid vision. Specific standards are reviewed with particular focus on frequency and voltage. Major grid protection concerns due to interconnection of high penetration DG are investigated and explored and presented using a utility grade computer program to verify the validity of the concerns. Updates and changes to current standards are desirable to alleviate specific limitations. Viable solutions to overcome these limitations are proposed and further research needs are identified.

Review of ferroresonance in power distribution grids

Ferroresonance is a special case of resonance, which can occur when a non-linear inductive reactance is connected in series with a capacitive reactance. In instances of ferroresonance involving electric power distribution facilities, the inductive reactance will be the magnetizing reactance of a single-phase or three-phase transformer. The capacitive reactance will be due ordinarily to the conductor-to-sheath capacitance of primary cable supplying the transformer under favorable conditions. Ferroresonance may be accompanied by abnormally high or low voltages as a result of single pole switching of one or two phases of the source supply to the transformer. Ferroresonance is capable of producing sustained overvoltages with peak magnitudes approaching, or exceeding twice the rated peak voltage, which is harmful and unsafe for the operation of most equipment. In this paper, the various conditions giving rise to occurrence of ferroresonance will be identified. The most prevalent resonance resulting in undesirable voltage conditions will be addressed and analyzed. Also some possible means of preventing occurrence of unsafe ferroresonance in power transformers will be proposed.

Standards, rules, and issues for integration of renewable resources

The purpose of this paper is to gather and document the existing criteria, rules, and practices used by the Investor Owned Utilities (IOUs) in California for physical interconnection of Distributed Resources (DR). The criteria set by the National Standard IEEE 1547, State of California Public Utilities Commission (CPUC) Rule 21, and the standard practices used by a sample major IOUs will be presented and compared. Adequacy, practicality, and controversial implementation problems associated with the presently used rules and criteria will be documented and discussed. Suggestions and recommendations for future research and studies in the interest of practicality and implementation uniformity will be identified.

Review of Concepts to Increase Distributed Generation into the Distribution Network

Distributed Generation (DG) level of penetration is expected to be increasing due to the state and federal governments mandates for utilization of renewable resources. The current Distribution Network (DN) was not originally designed for integration of DG at high penetration levels. Improvements will need to be made to DN to facilitate safe and reliable interconnection of DG at higher penetration levels. This paper gathers and documents the major concerns such as, voltage, protection, and power quality related to DG interconnections as well as the issues with the existing design standards and criteria. Several different DN changes have been proposed to help resolve these issues. The focus of this paper is about the existing DN topology and DG integration issues, as well as documentation and discussion of the proposed solutions. Additional areas of research are identified for further consideration.

Federated ensemble Kalman filter in no reset mode design

The main contribution of this paper is to design a more accurate optimal/suboptimal fault tolerant state estimator. Federated filters compose of a set of local filters and a master filter, the local filters work in parallel and their solutions are periodically fused by the master filter yielding a global solution. Federated ensemble Kalman filter no reset configuration is developed for multi-sensor data fusion. Ensemble Kalman filter(ENKF) estimation is widely used, where the models are of extremely high order and nonlinear, the initial states are highly uncertain, and a large number of measurements are available. ENKF is used as local filters in federated filter no reset mode design. Fault detection and isolation (FDI) algorithms is applied to local filters outputs. Faulty local filters are isolated and not fused by master filter to get a fault tolerant filter. Simulation results demonstrate the validity of the proposed filter formation.

Volt/VAr regulation and issues with high penetration of renewables on distribution systems

Penetration levels of renewable resources on distribution systems are increasing due to the mandated programs and associated economic incentives. Therefore the effects of these interconnections on the systems will need to be studied and evaluated. This papers concentration will be on voltage profile of a distribution system subject to high penetration levels of different renewable sources such as; photovoltaic and wind generation plants. The study will take into account different generation patterns for Photo Voltaic (PV) and wind generations. The model will consist of wind and PV units connected to three distinct loads. Simulation results addressing irregularities in wind patterns and various energy absorption levels of PV farms are presented. Functionality of suitable Volt-VAr options and possibility of controls using multi-objective optimization techniques have been proposed.

Modeling and controlling 3D formations and flocking behavior of unmanned air vehicles

This paper deals with the problem of modeling and controlling dynamic formations and flocking behavior of unmanned air vehicles. Dynamic formations are modeled using 3D kinematic models combined with dynamic graph structures. The leader-follower and co-leader interconnections are described by time-varying matrices that consist of a binary connectivity matrix and shape matrices. The control laws allowing to maintain the formation with stable motion are decentralized and reactive. They consist of linear navigation laws with deviation terms. These laws are used to generate trajectories to reach the goal and/or switch from one configuration to another. All geometric shapes are obtained from a basic shape that consists of a triangle. Thus any formation is a collection of triangles. To simplify the modeling and control tasks, a cylindric coordinate system is used and the three dimensional workspace is resolved into horizontal and vertical planes. The vehicles are then controlled in the horizontal and vertical planes separately.

Solar energy in a volume and efficiency in solar power generation

Solar power received on the surface of any object on the earth could be considered as the power absorbed in the entire volume of that object and hence measured in Watts per unit volume. In this paper, effectiveness of measuring power and energy per unit volume and the impact of height in system efficiency is analyzed. Variations in solar radiation intensity based on the angles of the Sun during the day and the year is briefly reviewed. It is shown how the wide ranges of these variations can affect efficiency of a solar power generating system and its energy delivery. Module of Irradiance and Collectivity Factors are introduced as parameters to estimate power/energy entering a volume and the efficiency of the system. Cost efficiency of the system is discussed considering all high cost items such as land, collector equipment and the supporting structure. A solar power-tracking concept is analyzed and shown how it would significantly increase the efficiency of the system. Feasibility of tracker in solar power generation is studied based on Tracking factor as defined here.