Renke Huang

Smart Grid Technologies for Autonomous Operation and Control

This paper presents a new smart grid infrastructure for active distribution systems that will allow continuous and accurate monitoring of distribution system operations and customer utilization of electric power. The infrastructure allows a complete array of applications. The paper discusses four specific applications: a) protection against downed conductors; b) load levelization; c) loss minimization; and d) reliability enhancement.

Advanced Distribution Management System

This paper proposes an advanced distribution management system (DMS) that a) monitors each component and performs protection functions using a dynamic state estimation, b) the estimated states are transmitted to the DMS where the real time model of the entire feeder is synthesized, c) uses the real time model to perform upper level optimization (operations planning) and lower level optimization (real time control) via a hierarchical optimization procedure; and d) applies proper controls to operate the system at optimal points. The proposed approach for protection, operations planning, and real time control of the system provides the infrastructure for additional important applications. As an example, the paper presents a novel application for monitoring available reserves from all resources in the system. We propose the concept of Reserve-O-Meter that monitors in real time the available reserves from all resources (utility and customer owned).

Wide area dynamic monitoring and stability controls

This paper presents a new approach for wide area dynamic monitoring of the system with many possible applications. One such application is discussed to provide real time stability controls. The new approach utilizes a substation based dynamic state estimation. The substation based dynamic state estimation uses data from relays, PMUs, meters, FDRs etc in the substation only thus avoiding all issues associated with transmission of data and associated time latencies. The substation based dynamic state estimator provides accurate representation of the dynamic state of the system. The dynamic state estimator runs at rates comparable to the suggested rates in the synchrophasors standard C37.118. Presently it has been implemented to execute 10 times per second thus providing the dynamic state of the substation 10 times per second. The results of the substation based dynamic state estimator are transmitted to a central location for monitoring the dynamic state of the system. A major advantage is the fact that only the dynamic state of the substation is transmitted instead of the raw PMU data that typical wide area monitoring implementations use. Note that the data describing the dynamic state is much less that the raw data of the PMUs. This fact facilitates the speedier transmission of the data in addition to the advantage of a more accurate dynamic state as opposed to the raw data. This infrastructure can be used for a number of applications. The paper focuses on transient stability monitoring, identification of out of step conditions and control. We propose an approach that is based on accurate evaluation of the system energy function (Lyapunov indirect method) and extraction of stability properties from the energy function. Specifically, we provide a methodology for determining the required data accuracy for the reliable real time estimation of the energy function. When the data meet these requirements, the estimated energy function can be visualized and animated providing a powerful visual tool for observing the transient stability or instability of the system. The infrastructure of the substation based dynamic state estimator provides the required accuracy and the ability to predict instabilities before they occur.

A predictive out of step protection scheme based on PMU enabled dynamic state estimation

This paper presents a predictive energy based Out of Step Protection scheme. It is based on real time dynamic monitoring of the system achieved through the implementation of a distributed, substation based dynamic state estimator. The estimator utilizes only local measurements and requires PMU synchronized measurements; additional measurements from non-GPS synchronized relays are also utilized and increase the redundancy of the system. The dynamic state estimator provides the evolution of the dynamic state of the system (real time dynamic model) at rates of 60 times per second. The real time dynamic model of the system is then utilized to evaluate the systems energy function based on Lyapunovs direct method and extract stability properties from the energy function. Comparison of the proposed approach to conventional Out of Step protection schemes (based on impedance relays) is demonstrated through illustrative examples. The proposed method detects out of step conditions much earlier than conventional methods.

Object-oriented 3-Phase distributed dynamic state estimator

This paper presents a suite of two distributed dynamic state estimators (QSE and DSE) that are performed at the substation level. The algorithm uses local GPS-synchronized and conventional non-synchronized measurements in the substation of interest for estimating the states of the substation as well as the states at the other ends of the transmission lines at the adjacent substations. The estimation algorithm provides the true dynamic (transient) states of the system. As such it provides the basic infrastructure for highly accurate real time dynamic monitoring and control at speeds that are not presently available. Numerical experiments on the NYPA Gilboa-Blenheim substation are presented in this paper for the purpose of evaluating the performance of the proposed algorithms. It is shown that the proposed algorithm is reliable and feasible for practical implementation.

Substation based dynamic state estimator - numerical experiment

This paper presents a distributed dynamic state estimation algorithm that operates on the substation level. The algorithm uses local GPS-synchronized and conventional non synchronized measurements in the substation of interest and can estimate the states of the local substation as well as the states at the other ends of the transmission lines at the neighboring substations. The estimation algorithm provides the true dynamic (transient) states of the system. As such it provides the basic infrastructure for high accuracy real time dynamic monitoring and control at speeds that are not presently available. Numerical experiments are presented in this paper for the purpose of evaluating the performance of the proposed algorithm. It is shown that the proposed algorithm is reliable and feasible for practical implementation.

Self-powered smart meter with synchronized data

In this article, a notably advanced meter with real-time data detection capability, high reliability, self-powered and low fabrication cost is presented. It is intended for use in smart grid applications. Compared with the old local grid, knowing the system status in real time is achieved as a first step to control a smart grid reliably. Our framework provides insights about an energy harvesting sensor network to monitor the smart grids power distribution. This provides the information needed to make a compromise between efficiency and reliability of the whole grid system. The meter design shown in this paper operates automatically and is considered with installation difficulties and environmental effects such as position displacement due to weather, electrical and magnetic field interaction and so on. Each meter collects current, voltage and associated phase angles and proceed to carry a two-way communication to form a sensors net using XBee-PRO DigiMesh 2.4 which is a RF commercial communication module.

Implementation of a 3-phase state estimation tool suitable for advanced distribution management systems

A state estimation tool is presented which is suitable for distribution system real time monitoring. The tool is considered to be a critical component of a smart grid infrastructure that will enable modernization of the distribution grid. The proposed estimator is advantageous compared to currently available estimators for two reasons. First, it is based on a three phase physical model of the distribution system. Moreover, it utilizes synchronized measurements available from a novel proposed device (UGPSSM). The synchronized measurement set combined with conventional non-synchronized measurements from SCADA systems results in improved solution and convergence speed. Reporting and visualization tools are also developed in order to make it a user friendly tool for the operators in the DMS. The state estimator provides the operator with a highly accurate real time model of the distribution system that can be used in various applications including Volt/Var control, load levelization and reliability enhancement.

Integrated Smart Grid Hierarchical Control

A previous paper presented a new smart grid infrastructure for active distribution systems that will allow continuous and accurate monitoring of distribution system operations and customer utilization of electric power. This paper presents the utilization of this system for the purpose of optimizing the operation of the system over a rolling planning horizon. Specifically, we propose the use of a hierarchical optimization method that optimizes the operation of the system by scheduling the operation of various resources with storage capability. The hierarchical method has three levels: (a) distribution feeder optimization, (b) substation level optimization, and (c) system optimization. At the lowest level (feeder optimization) the problem is formulated as a quadratic optimization problem that is solved via barrier methods. At the higher levels the problem is formulated as a stochastic dynamic programming problem. The proposed method captures the uncertainty associated with many resources in the system resulting from the integration of renewables. Finally, a method is proposed for the business case analysis of the benefits of the proposed scheme and results for a hypothetical system are presented.

Smart Grid Infrastructure for Distribution Systems and Applications

This paper presents a new smart grid infrastructure for active distribution systems that will allow continuous and accurate monitoring of distribution system operations and customer utilization of electric power. The infrastructure allows a complete array of applications. The paper discusses four specific applications: (a) protection against downed conductors, (b) load levelization, (c) loss minimization and (d) reliability enhancement.