M. Vaziri

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.

Type-2 fuzzy multiagent traffic signal control

This paper proposes a controller design for urban traffic networks. The growing demand for faster transportation has led to heavy congestion in road traffic networks, necessitating the need for traffic-responsive intelligent signal control systems. The developed signal control system based on uncertain information of the environment must be capable of determining the green time that minimizes the overall delay. The proposed traffic controller is based on distributed multi-agent approach which is very efficient considering the uncertainties and parameter variations. The effectiveness of the proposed control method is verified by comparing the obtained result with that of a fixed time controller.

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.

Complex power optimization of photovoltaic systems

Interconnection of Photovoltaic (PV) systems as Distributed Generation (DG) sources to the distribution circuits are rapidly increasing due to their benefits and low maintenance. However, massive penetration of these systems will result in issues which can impact the operation, controls, and protection of the grids. One of these issues is related to extra injection of power during daytime with high irradiation, which results in the backflow of power and system overvoltages. Current regulations do not allow photovoltaic inverters to participate in voltage or reactive power control. Hence, photovoltaic inverters are only allowed to inject active power to ensure maximum profits for investors. From the systems perspective, however, this type of operation may not result in the best practice. The goal of this paper is to show that coordinated active/reactive power control of the PV inverters can resolve the issues associated with voltage profile, while reducing the total demand of the system from the Utilitys perspective. For this purpose, a nonlinear optimization problem has been defined in which total demand of the system is minimized, considering system constraints such as voltage profile and line flows. Simulations on the IEEE 34 bus test system show that the proposed practice can significantly improve the system behavior.

A novel state estimation formulation for distribution grids with Renewable Energy Sources

Interconnection of Distributed Generation (DG) using renewable resources to the distribution networks in on the rise. Distribution grids having DG interconnections at higher penetration levels are challenged for more accurate monitoring and controls. In this paper a novel approach and a theoretical formulation of state estimation is proposed for distribution grids with Renewable Energy Sources (RES). The recommended formulation pertains to an optimization algorithm with variable weighting factor for a more precise estimation of the system states. The formulation can serve as as a general framework for a self-adapting dynamic estimator for improved states forecasting and thus preventive control of the distribution grid. Precisely estimated system states can also serve beneficial in; optimal scheduling, security assessment, and real time transactions.

Higher I 2 t stress on equipment due to increased penetration of Distributed Generation

Increased penetration of Distributed Generation (DG) raises the total I2t levels on the power distribution network. Increased level of I2t is directly related to the stress levels impressed on the equipment during short circuit faults. In this paper, the definition and significance of I2t as it relates to increased stress level of equipment are explained. It is reconfirmed through simulations that increased penetration of DG leads to higher levels of total I2t at every fault location. It is shown that I2t supplied by the DG rises with higher penetration levels, confirming previous findings. The results also indicate that I2t supplied by the substation decreases which contradicts previous research. Four types of short circuit faults, including 3Phase, Line to Line(L-L), Line to Line to Ground(L-L-G) and Single Line to Ground(1L-G) faults are simulated on the IEEE 34-node test feeder, modified with 24 buses using two different programs known as Electrical Transient and Analysis Program (ETAP®) and Advanced Systems for Power Engineering (ASPEN®). Simulation data from both programs indicating higher confidence in accuracy due to close agreement between the results has been presented.

A heuristic power optimization method for photovoltaic systems

California is striving to increase penetration of Distributed Generation (DG) to 33% by 2020. This effort is to promote energy independence of the state of California and to lead the country to be more environmentally conscious. However, integrating DG and increasing penetration to high levels will negatively impact the grid. One issue that has been discussed is that DG may supply more power than is demanded by the load. This may cause overvoltage issues at the buses where the DG is connected and also may cause power to flow from the distribution to the transmission system. Current legislation dictates DG to operate at unity power factor and prohibits DG to inject or absorb reactive power. This is to ensure that the Utilities can control system voltage and that the customers do not regulate voltage at the interconnection points. However, when considering system performance, this legislation is not ideal. The mission of this paper is to provide convincing data that will demonstrate the benefits of controlling reactive power for better system performance. Furthermore, it will provide a heuristic method that calculates near-optimum dispatch of DG in the distribution system in a fast approach which could potentially be implemented in practical, real-time applications.