Increased availability of controllable devices and overall visibility means that distribution systems can now be planned and operated in a more optimal way. However, to achieve this, it is crucial to have the underlying tools for determining these optimal decisions and settings. The work in this study discusses the formulation for a three-phase unbalanced distribution optimal power flow. The metho...

The distributed energy resource (DER) hosting capacity of distribution feeders is commonly analyzed with scenario-based methods considering assumed worst-case scenarios such as minimum and maximum load conditions. For distribution feeders with load-tap changers, line voltage regulators, or capacitor banks, it can be challenging to accurately identify the realistic worst-case conditions that limit the hosting capacity. In particular, considering only minimum and maximum load conditions may not correspond to the feeder worst-case scenarios and may lead to under or over estimating the hosting capacity. This paper proposes a scenario-selection method for hosting capacity analysis, which identifies the feeder key load conditions and the corresponding voltage regulation equipment states for accurate determination of hosting capacity.

This paper investigates the influence of a mix of smart inverter functions of photovoltaic (PV) systems in different operating conditions of a real distribution feeder. The analysis considers the connection of three PV systems and three smart inverter functions to be combined: volt-var, volt-watt and fixed power factor. For instance, a combination can be formed by selecting one PV system with its inverter operating in volt-var mode, another one operating in volt-watt mode and the last one in fixed power factor mode. The benefits and impacts of each mix of smart inverter functions is measured by considering different operating conditions. For this purporse, three penetration levels, two load levels and two solar irradiance profiles are considered. The influence of each combination of functionalities is investigated through several metrics that have been created to reflect the overall system performance. Some metrics are, for example, maximum feeder voltage, number of traditional voltage regulation equipment operations, reactive energy demanded by the inverters and many others.

Distribution power systems are evolving due to the incorporation of emerging technologies such as intelligent electronic devices, smart inverters and distributed energy resources requiring distribution engineers to have access to power system analysis tools that support the changing design and time-based features of such systems. The power system analysis tools should harmonize the new technologies in a way that autonomous and interconnected systems can be automated, simultaneously operated and visualized for maximum grid benefit by distribution engineers.Classic analysis based on static snapshots of loading is an inadequate practice for scheduling future investments in distribution systems and distribution management systems. This is a common practice that has been used for decades to maintain power systems over time. However, the needs of future systems require the integration of modern computing technologies and interfaces with advanced distribution system analysis. This accelerates the analysis and providing to the distribution engineer the information to make the right choice.In this paper, we discuss the needs mentioned above, and propose a flexible framework to support the development of distribution systems analysis. This multidisciplinary framework is supported by a set of open source tools developed by EPRI and other parties for presenting a modular approach to enable the next generation of distribution system analysis tools. These tools have been developed to advance the capabilities EPRI’s Open Source Distribution System Simulator OpenDSS to guide the industry on the distribution power system analysis tools and techniques.

Distributed energy resource (DER) hosting capacity of distribution feeders is commonly analyzed with scenario-based methods assuming specific load conditions. For feeders with existing DER, additional processing is necessary to capture conditions of these DERs, that can impact hosting capacity indicators. Only modeling min/max scenarios for the load and DER may not represent realistic worst-case scenarios and may lead to under- or over-estimating the hosting capacity. This paper proposes a method based on historical data that determines a set of scenarios which captures worst-case conditions and enables accurate determination of hosting capacity values. This paper also proposes a probabilistic hosting capacity analysis method that provides valuable information for robust system planner decisions.

The power system is currently undergoing a major transition, with increasing levels of renewable resources being connected to the grid and displacing conventional generation. Many of these resources are connecting not to the transmission system, as had been the convention in the past, but directly to the distribution system in the form of distributed energy resources (DERs). With the introduction ...

Owing to the energy policies and the consequent transition to renewable energy sources, the amount of photovoltaic (PV) installations is continuously increasing in many countries. As PV inverters utilise power electronics, its impact on power quality is an important concern for manufacturers, planners, solar power operators and utilities/network operators. The International council on large electric systems (CIGRE) working group C4/C6.29 has studied many aspects related to PV installations and its impact on power quality. To incorporate the existing experiences with power quality issues related to solar power, an international survey has been conducted by the working group. The survey has found that there is a significant lack of information among utilities/network operators with respect to the possible impact of PV installations on power quality. It is recommended to intensify the monitoring of PV installations in order to obtain sufficient information for a reliable assessment of its impact on power quality.

As residential customers continue to connect distributed energy resources (DERs) with smart inverters unto distribution systems, distribution engineers face new challenges of accurately modelling residential smart inverters for distribution system optimisation. Depending on the coordination strategy, the impact of these DERs can represent a positive contribution to the system operation. However, if the coordination strategy does not consider the interaction between DERs and the distribution system for clustering them, the distribution system integrity can be compromised. This study describes an approach to group smart inverter photovoltaics (PVs) deployed within a secondary circuit (low-voltage system) to enable the correct monitoring and control of these smart inverters. It further explains the process used to coordinate clustered smart inverter PVs to enhance distribution operation optimisation.

The ability to establish the limits of distribution feeders is crucial from a distribution planning perspective. Particularly when the recent emergence of distributed energy resources is considered. Planners need to ensure that the addition of these resources to distribution systems will not result in violations of feeder limits, and be aware of the point at which system upgrades or management schemes need to be considered. The work in this paper employs a three-phase optimal power flow formulation to determine generic feeder hosting capacities for load and generation. Various hosting capacities are assessed, with the purpose of providing distribution system planners with critical information regarding the limits of their feeders. The formulation detects locations that may be troublesome, and defines the limiting factors of the feeder.

Combined installations of solar photovoltaics (PV) and energy storage devices are increasingly being considered, both to combat the intermittent nature of PV and to provide additional services to the grid. This work details the integration of one such system. The impacts of installing a distributed PV and storage system under various feeder conditions, locations and control strategies are examined. The results provide an indication of where best to locate the system, how to control it and what additional services it can provide to the local feeder.

The Role and operation of the U.S. electric power system is changing as a result of policy incentives, technological improvements, and consumer choices in technology and service. Consumers have increasing choice and control over their electricity service. The range of choice is diverse: owning or leasing on-premises generating systems [such as solar photovoltaic (PV), wind, and combined heat and power systems], subscribing to services with dynamic pricing and undertaking energy efficiency measures to save money by controlling electricity use, and using storage devices to manage when and how they consume grid-supplied electricity. Collectively, these demand-altering measures are referred to as distributed energy resources (DERs).

The increasing use of solar power connected to the public grid and the associated concern for deteriorating power quality triggered the formation of a joint working group with the aim to describe and quantify this impact. The WG formed in 2012 as a joint C4/C6 effort, formed to examine the power quality aspects of solar power, specifically addressing a number of phenomena, all which will be discussed in this study.

Nowadays, planning studies for distribution power systems require the inclusion of non-conventional loads. These loads refer to devices that converts energy integrating multiple functionalities not included in traditional simulation tools. These technologies are continuously changing and adding new functionalities that need to be tested before being implemented by utilities. However, most available simulation tools cannot respond to the rate of these changes because of either inadequate information on the power system equipment, several release of various versions of power system equipment, and some of these newly developed power system equipment/devices are too specialized; hence difficult to interface with the existing power system, among other issues. This paper presents a methodology for modeling new power system equipment technologies using Open Source Simulation Tools. The simulation tool proposed in this paper is EPRI Open Source Distribution System Simulator OpenDSS. By using OpenDSS, we discuss the implementation of a new energy storage device, which has smart inverter capabilities, and how to model it for a fast implementation in detailed daily simulations. The proposed methodology is a simple co-simulation technique to incorporate recent technologies on an existing distribution system; within existing simulation packages.

To support distribution planning and operations engineers, this paper describes an optimal methodology for specifying smart inverter settings that will improve photovoltaic (PV) integration into distribution systems. The dynamic nature of the distribution system requires that a range of load and solar conditions be considered for this purpose. Time-series analysis was performed using Open-source Distribution System Simulator modeling environment to determine the overall impact on the distribution feeder. For the feeder investigated, the use of smart inverters was evaluated for mitigating potential voltage-related issues by reducing the magnitude and/or number of American National Standards Institute (ANSI) voltage violations, as well as meeting other objectives like increasing in substation power factor and reducing distribution system losses.

Distribution planners are being faced with a new reality — the vast majority of change to the distribution system is occurring due to the addition of distributed energy resources (DER). The result is a new set of challenges when planning and integrating DER. Just as capacity planning studies are performed for accommodating new load, hosting capacity planning studies are needed for accommodating new DER. To meet this challenge, the industry needs a system-wide method to plan for and integrate DER into the distribution system. This paper will describe the Distribution Resource Integration and Value Estimation (DRIVE) module developed by EPRI, the implementation of that module in distribution planning software, and the data needed to successfully use this module to determine distribution-wide hosting capacity.

This paper examines the grid impacts of utility-scale solar photovoltaic (PV) systems when they are installed on both the transmission/subtransmission and distribution systems simultaneously. A baseline analysis is performed to characterize grid performance using actual data from an operating 32 MW solar PV system installed at the subtransmission system, and a 1MW solar PV system installed on a neighboring distribution system. The analysis is performed by developing computer models of the combined systems using an OpenDSS software platform. Various penetration levels of solar PV are then examined by adding "virtual" solar PV generation to the system to examine the grid impacts of different penetration levels of solar PV. The use of smart grid inverters to provide ancillary grid services is also examined as a means of mitigating grid impacts caused by the solar PV systems.

The fourth solicitation of the California Solar Initiative (CSI) Research, Development, Demonstration and Deployment (RD&D) Program established by the California Public Utilities Commission (CPUC) supported the Electric Power Research Institute (EPRI), National Renewable Energy Laboratory (NREL), and Sandia National Laboratories (SNL) with data provided from Pacific Gas and Electric (PG&E), Southern California Edison (SCE), and San Diego Gas and Electric (SDG&E) conducted research to determine optimal default settings for distributed energy resource advanced inverter controls. The inverter functions studied are aligned with those developed by the California Smart Inverter Working Group (SIWG) and those being considered by the IEEE 1547 Working Group. The advanced inverter controls examined to improve the distribution system response included power factor, volt-var, and volt-watt. The advanced inverter controls examined to improve the transmission system response included frequency and voltage ride-through as well as Dynamic Voltage Support. This CSI RD&D project accomplished the task of developing methods to derive distribution focused advanced inverter control settings, selecting a diverse set of feeders to evaluate the methods through detailed analysis, and evaluating the effectiveness of each method developed. Inverter settings focused on the transmission system performance were also evaluated and verified. Based on the findings of this work, the suggested advanced inverter settings and methods to determine settings can be used to improve the accommodation of distributed energy resources (PV specifically). The voltage impact from PV can be mitigated using power factor, volt-var, or volt-watt control, while the bulk system impact can be improved with frequency/voltage ride-through.

This paper describes methods that a distribution engineer could use to determine advanced inverter settings to improve distribution system performance. These settings are for fixed power factor, volt-var, and volt-watt functionality. Depending on the level of detail that is desired, different methods are proposed to determine single settings applicable for all advanced inverters on a feeder or unique settings for each individual inverter. Seven distinctly different utility distribution feeders are analyzed to simulate the potential benefit in terms of hosting capacity, system losses, and reactive power attained with each method to determine the advanced inverter settings.