Mallikarjuna R. Vallem

Siting and sizing of distributed generation for optimal microgrid architecture

This paper presents a method for optimally siting and sizing distributed generation (DG) units in a microgrid. The optimization is based on stipulated reliability criteria. Power system planning based on reliability gives rise to efficient architectures which can meet the consumer requirements with minimum system upgrade. This paper develops a technique for determining the optimal location and sizes of DG units in a microgrid, given the network configuration and the heat and power requirements at various load points. The method is based on simulated annealing. Thermal output and utilization of combined heat and power (CHP) units are considered. The paper presents the development and implementation of the method, and demonstrates its application on a six bus test system.

Determination of Storage Required to Meet Reliability Guarantees on Island-Capable Microgrids With Intermittent Sources

It is well known that the presence of energy storage ameliorates the reliability challenges posed by intermittent sources. However, a quantitative assessment of the exact amount of storage required to meet a reliability target or guarantee in the presence of intermittent sources is not trivial. This paper describes a practical approach to achieving this. First, an analytical approach is developed for determining the amount of storage required to meet a reliability target at a specific load point. Then the method is extended to a more complex island-capable microgrid system where initial reliability assessment and final verification of reliability guarantee are performed using sequential Monte Carlo simulation. The necessary component and system models are developed and described, and a mock military base is used to demonstrate the method. The work reported was performed under a contract from Sandia National Laboratory to determine storage need in order to provide reliability guarantee on an island-capable military microgrid, but the approach applies as well to civilian systems, both islanded and grid-connected. A method for determining an optimal storage mix is also developed.

Distributed Generation Placement for Optimal Microgrid Architecture

This paper describes a method for siting of distributed energy resources (DER) within the framework of an optimal microgrid architecture. An optimal microgrid architecture is characterized by minimum cost interconnection, sizing, and siting of DER subject to stipulated global and local reliability criteria. This paper addresses the siting aspect of optimal microgrid architecture. The siting problem considers factors like deployment costs and savings gained by the use of combined heat and power (CHP). The problem is formulated as one of nonlinear programming and simulated annealing optimization is applied. This paper presents the development and implementation of the method, and demonstrates it using a six bus test system

Optimal deployment of distributed generation using a reliability criterion

This paper presents an optimal planning approach toward the design of cost-efficient and reliable microgrids. The proposed approach uses simulated annealing (SA) to determine the optimal size and location of a mix of distributed generation (DG) candidate technologies to achieve stipulated reliability criteria. The deployment plan consists of adding suitable quantities of DG at appropriate locations, and is optimal in that the cost of expansion is minimized. The paper develops the models and the approach, and describes an SA-based implementation. The method is demonstrated on a standard test system, and the application of the method as a planning tool is illustrated by means of two case studies: 1) optimal expansion of an existing distribution system into a microgrid and 2) evaluation of the impact of projected prices on the deployment strategy. Relative penetration of different DG technologies is also analyzed.

Reliability Evaluation and Need Based Storage Assessment for Surety Microgrids

This paper presents a Monte Carlo simulation based approach to estimate the interruption duration distributions at the load buses in a micro grid for the determination of need based storage assessment. Energy limited nature of storage devices is considered for the reliability evaluation. Time variable load and generation profiles have also been incorporated in the method to obtain more practical distributions of interruption durations. The method is demonstrated on a ten bus test system and the results are explained.

GridPACK ™ : a framework for developing power grid simulations on high performance computing platforms

This paper describes the GridPACKTM framework, which is designed to help power grid engineers develop modeling software capable of running on high performance computers. The framework makes extensive use of software templates to provide high level functionality while at the same time allowing developers the freedom to express whatever models and algorithms they are using. GridPACKTM contains modules for setting up distributed power grid networks, assigning buses and branches with arbitrary behaviors to the network, creating distributed matrices and vectors and using parallel linear and non-linear solvers to solve algebraic equations. It also provides mappers to create matrices and vectors based on properties of the network and functionality to support IO and to manage errors. The goal of GridPACKTM is to substantially reduce the complexity of writing software for parallel computers while still providing efficient and scalable software solutions. The use of GridPACKTM is illustrated for a simple powerflow example and performance results for powerflow and dynamic simulation are discussed.

GridPACKTM: A framework for developing power grid simulations on high-performance computing platforms

This paper describes the GridPACKTM framework, which is designed to help power grid engineers develop software capable of running on high-performance computers. The framework makes extensive use of software templates to provide high-level functionality while still providing flexibility to easily implement a broad range of models and algorithms. GridPACKTM contains modules for setting up distributed power grid networks, supporting application-specific bus and branch models, creating distributed matrices and vectors and using parallel linear and non-linear solvers. It also provides mappers to create matrices and vectors based on properties of the network and functionality to support Input/Output (IO) and to manage errors. The goal of GridPACKTM is to substantially reduce the complexity of writing software for parallel computers while still providing efficient and scalable software solutions. The use of GridPACKTM is illustrated for a simple powerflow example and performance results for the powerflow and dynamic simulations are discussed.

Stochastic Operations and Planning

This document discusses PNNLs efforts to mitigate the changing patterns of electrical system behavior, how it is dispatched, and exchanges of energy.

Methods for reducing momentary interruptions in distribution systems

Momentary interruptions in the distribution system occur due to recloser operations and automated switching. With increasing use of reclosers and switching operations as part of distribution automation, momentary interruptions have become prominent causing concerns about reliability. This can affect the sensitive loads in the system. An innovative technique to reduce momentary interruptions and thus mitigate MAIFI in a distribution system is proposed in this paper. The proposed methods describe strategies with and without communication, for protection devices, to isolate the customers downstream of a fault before first reclosing operation of a recloser and thus reduce momentary blinks seen by customers on faulted feeder. The technique can be equally applied for topologies like radial, looped and meshed systems. The methods are demonstrated and results reported on a distribution backbone taken from Bus 2 of Roy Billinton Test System.

Hybrid cascading outage analysis of extreme events with optimized corrective actions

Power systems are vulnerable to extreme contingencies (like an outage of a major generating substation) that can cause significant generation and load loss and can lead to further cascading outages of other transmission facilities and generators in the system. Some cascading outages are seen within minutes following a major contingency, which may not be captured using only the dynamic simulation of the power system that are usually run for 30 or 40 seconds. The utilities plan for contingencies based on either dynamic or steady-state analysis separately, which may not accurately capture the effect of one process on the other. We addressed this gap in cascading outage analysis by developing the Dynamic Contingency Analysis Tool (DCAT), which can analyze the hybrid dynamic and steady-state behavior of power systems including protection system models in dynamic simulations, and by simulating corrective actions in post-transient steady-state conditions. One of the important implemented steady-state processes is to mimic operator corrective actions to mitigate aggravated states caused by dynamic cascading. This paper formulates an optimization model, called Optimal Power Flow with Corrective Actions (OPFCA), for selecting corrective actions that utility operators can take during major contingencies and thus automate hybrid dynamic/steady-state cascading outage mitigation. The improved DCAT framework with OPFCA is demonstrated on the 3120-bus Polish system.