Mohammad Vaziri

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.

An estimative approach for CVR effectiveness using aggregated load modeling

In order to develop an estimate of the benefits of Conservation Voltage Reduction (CVR) in the distribution system, composite characteristics of system loads based on ZIP modeling has been extracted from measurements of electrical quantities at the main substation. This knowledge is further used in finding a quantitative estimation approach for predicting the effectiveness of substation transformer tap changes in reducing total power demand in different load conditions. The proposed algorithm is implemented on the IEEE 34 bus test system and the results are demonstrated. It is shown that the method can predict the effectiveness of CVR with acceptable accuracy.

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.

A state-space model for integration of battery energy storage systems in bulk power grids

Applications of Battery Energy Storage Systems (BESS) in the power grids will be expanded in the coming years due to factors such as decreasing costs of such systems. In a modern power network, BESS systems can be optimally controlled for peak-load shaving and other ancillary services such as volt-var control, system balancing and loss reduction. However, all these “system-level” controls will depend on the capability of each individual BESS to independently control the active and reactive power injection/absorption at its connected bus, and to maintain the voltage of the DC link between its AC/DC and DC/DC converters. As a result, understanding the behavior and control requirements for the operation of the BESS is necessary. In this paper, an active AC/DC rectifier and a bidirectional DC/DC converter have been modeled and analyzed for charging and discharging of the batteries in a BESS system. The models used in these analyses have been developed based on an integrated state-space equation set for the converters and the battery. This type of modeling is proper for demonstration of the effects of massively integrated storage systems in the bulk power grids.

Fault detection and isolation in a DC microgrid using a central processing unit

The goal of this paper is to design a protection system capable of detecting, isolating and locating high and low impedance ground faults in a DC multi-terminal system using a Digital Signal Processing (DSP) based control unit. Due to low current fluctuations during faults, it becomes difficult to detect high impedance faults using conventional methods. In order to locate faults, the DC ring bus will be divided into different zones and an algorithm will be developed to monitor currents in each zone. The proposed method has been tested through examples and is seen to be cost effective and easy to implement.

Fuzzy type-2 electrode position controls for an Electric Arc Furnace

This paper presents an approach to fuzzy type-2 Proportional-Integral-Derivative (PID) controls for the electrode positions in an Electric Arc Furnace (EAF). Due to the fluctuating power requirements and associated uncertainties of the EAF during operations, use of an accurate membership function is unreasonable. Therefore, fuzzy type-2 sets is applied for EAF controls. In this paper it is also proved that by fuzzy type-2 logic, the performance characteristics of the system will be improved using the proposed method.

Kalman-Particle Filter Used for Particle Swarm Optimization of Economic Dispatch Problem

This paper presents an effective evolutionary method to solve the Economic Dispatch (ED) problem with units having prohibited operating zones. The Kalman filter is an efficient recursive filter that estimates the state of a dynamic system from a series of noisy measurements in the Total Power Generation (TPG). ED is an example of a dynamic system algorithm that has been widely used for determination most economical generation profile to optimize the overall electricity prices. ED is a non-smooth problem when valve-point effects of generation units are considered. This paper applies Kalman - Particle filter (KF-PF) to the ED state estimation problem that has been optimized with Particle Swarm Optimization (PSO), with the emphasis to avoid the solution being trapped in local optimas [1], [2]. Kalman and particle filter are used to estimate TPG as state of ED problem. The performance of the KF-PF has been tested on a typical system and compared with others proposed in the literatures. The comparison results show that the efficiency of proposed approach can reach higher quality solutions.