Rick Meeker

Dynamic interactions between distribution network voltage regulators for large and distributed PV plants

This paper summarizes the initial investigation of dynamic interactions of voltage regulating equipment when allowed to act together with one or more large voltage-controlled solar photovoltaic (PV) generation plants. The study results are based on an existing large PV plant and distribution circuit in the service area of a major electric utility. The existing feeder does not have any voltage regulating equipment and the PV plant is not allowed to control voltage, hence injects real power only. However, in light of the growing interest in allowing PV plants to control voltage, several scenarios are considered by allowing PV plants to control the voltage at the Point of Common Coupling (PCC) along with the traditional voltage regulators. Further case studies are performed by distributing the large PV plant into six PV plants of equal power rating connected at different feeder locations. This configuration has been investigated to determine possible differences in interactions of voltage regulators between a large plant and distributed plants. The voltage regulating equipment considered are On-Load Tap-Changing Transformers (OLTC), Switched Capacitor Banks (SCB) and also PV plant inverters capable of controlling the voltage at the PCC. The 12.6 MW (peak a.c.) PV plant and its controls, the regulating equipment, and the distribution network are modeled using a Real Time Digital Simulator (RTDS). Initial study suggests that allowing PV plants to actively participate in the voltage control process requires a coordinated control to minimize the number of operations of traditional voltage regulators.

Impact of PV on distribution protection system

This paper investigates the impacts of PV interconnection on the protection systems of a distribution network, especially when power flow is reversed in high penetration scenarios. A Florida based substation and its six-feeders were selected for the study. The system was slightly modified to make it a notional system that still closely represents the actual system behavior from the point of view of system protection. The main modification is in the representations of loads, where all the loads were represented by fewer aggregated loads on each feeder. One of the feeders is 9 miles long and has a 12.6 MW (AC) PV plant connected to the primary side of the feeder at a distance of 4.8 miles from the substation. The feeder has an average load of approximately 11 MVA that makes it a contender for a high penetration (more than 100%) feeder when PV reaches its peak generation. The model of the entire substation, its feeders and protection system has been built using a high fidelity transient simulation tool RSCAD. Initial simulation results indicate that if protection devices are coordinated properly, a reverse power flow does not create any nuisance trip or malfunction of the protection system. However, based on the location of the PV plant with respect to the fault, slight change in the trip time of the time-overcurrent relays was observed.

Research Perspectives on High-Fidelity Modeling, Simulation and Hardware-in-the-Loop for Electric Grid Infrastructure Hardening

This panel paper discusses the roles of high- fidelity modeling and simulation in electricity grid infrastructure hardening research initiatives. The concept of hardware- in-the-loop based research for electric power systems is revisited, with particular focus on controller-hardware-in-the-loop (CHIL) and power- hardware-in-the-loop (PHIL). Some examples of current and future research activities in CHIL and PHIL relating to electricity grid infrastructure development are described in detail.

Voltage Sensitivity to Capacitor Switching on an Existing Fixed Speed Induction Generator Wind Farm

Switched capacitors at wind farms employing fixed speed induction generators are intended to provide reactive power support to control and maintain the voltage at the point of common coupling (PCC) within acceptable operational values. Malfunction of the capacitor switching control may lead to voltage depression and, subsequently, to tripping of turbines which could create additional transient power quality disturbances. This paper presents results of simulations of voltage regulation problems of an existing wind farm on the Bonneville power administration (BPA) system where voltage regulation problems have led to the study of possible dynamic voltage compensation schemes to minimize the problem. SCADA data for real and reactive powers and voltage have been analyzed against results from simulation models to verify the behavior and confirm the mechanisms associated with the voltage regulation problems. Other aspects associated with the high fidelity modeling of the wind farm and issues about the sizing of a possible dynamic voltage controller are investigated.

Testing the “smarts” in the smart T & D grid

The growing sophistication and complexity of power system control apparatus and systems plus the addition of new topological features such as distributed generation at the distribution level requires new test environments which can evaluate and optimise these systems prior to deployment in the real system. One such environment is described in this paper along with examples of its use in evaluating application scenarios involving both real and simulated parts of a controlled power system. Future developments in the capability of such environments is briefly described.

Impacts and interactions of voltage regulators on distribution networks with high PV penetration

This paper discusses the impacts and interactions of voltage regulation devices on systems with high PV penetration under different solar conditions and voltage control algorithms. The study is done using a tool that was developed under a Department of Energy (DOE) funded project, Sunshine State Grid Initiative (SUNGRIN). The tool is composed of Matlab scripts and functions that use a Component Object Model (COM) interface to communicate with the Open Distribution System Simulator (OpenDSS) developed by EPRI. The tool is applied in this paper to analyze and study the dynamic interaction between voltage regulation devices in a distribution network, and the impacts that photovoltaic (PV) systems have on the operation of these devices in the network. A real feeder from a Florida-based utility has been used to perform this study with different incident solar radiation (insolation) scenarios. Case studies show the difference in the activity of the voltage regulating devices with the variation of PV power injection to the grid. The case studies also investigate the impacts of allowing PV systems to participate in voltage regulation using different algorithms.

Projected load and generation data in support of an open access notional dynamic model of the Florida grid

In support of work to assess and ensure the reliability and resiliency of Floridas power generation, transmission, and distribution system as load and generation evolve in future years, groundwork is presented for the development of an open, dynamic model of the Florida grid and geographically distributed projections for growth in load and generation within the state. Using load forecasts provided by the states major utilities, in conjunction with geographical population projections, load projections are developed for each of the states counties. Projected load information is to be combined with both planned generation and information regarding the potential for renewable energy resources that may be brought to bear, in order to provide a probabilistic view of the future loads and insight into potential generation growth within the state for assessing the suitability and potential needs of Floridas power grid in an open research context. The framework for a flexible and representative model of Floridas electric power system is subsequently presented, and initial efforts toward construction of the model are discussed.

High Penetration Solar PV Deployment Sunshine State Solar Grid Initiative (SUNGRIN)

Disclaimer: This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. Acknowledgments The work described herein was made possible by the dedication and commitment of the SUNGRIN projects electric utility partners and industry suppliers who provided information on high penetration PV circuits for analysis, valuable input and perspective on real-world issues and challenges, review of project activities and results, and in-kind cost share contributions to completion of the total effort: University partners also played a vital role, particularly in completing the research and analytical work. (UCF) made major contributions in data collection and studies of the solar resource throughout the course of the project, and

Modeling and validation of a utility feeder for study of voltage regulation in the presence of high PV penetration

A Florida utility feeder with a high penetration level of solar photovoltaic (PV) generation was modeled in RTDS/RSCAD. The feeder model was validated by comparing the results in different simulation tools, and using field measurements and short circuit data provided by the utility. The feeder has 2.6 MW of PV which is approximately 30% penetration (comparing with peak load). The feeder has a step voltage regulator (SVR) and 4 switched capacitor banks (SCBs) installed to regulate voltage. Studies were conducted to analyze feeder voltage characteristic for the existing circuit configuration and operating scenarios. Additional studies were conducted to determine the potential impact of additional PV penetration that might happen in the future. Validation results show full agreement with the software based validation and a reasonably acceptable match with the field data collected from different locations on the feeder.

Characterizing Solar PV Output Variability and Effects on the Electric System in Florida, Initial Results

This paper shares initial results from a major collaborative project in Florida underway to study and address effects of high penetration levels of solar photovoltaic (PV) generation on the electric power system. The effort includes characterizing the variability of the solar resource in Florida, where a number of new multi-megawatt solar projects have either recently come online or are in the planning or construction stages (including the largest solar PV generating station in N. America at the time of this writing). Until now, most work on characterizing solar variability has focused on the Southwestern U.S. This paper shares initial results and insights on the variability of Solar PV generation output in Florida on different timescales and provides some preliminary insights into the implications and effects of the variability on the successful integration of increasingly higher penetration levels of solar PV, with respect to the integration technology, control systems, and the electric power system.Copyright