Utility Distribution System Research Articles

Construction of Utility Tunnel power supply and distribution system

As an underground structure that can accommodate multiple municipal pipelines, the utility tunnel can not only coordinate the planning, construction, and management of various municipal pipelines, but also achieve intensive development of urban underground space. In theory, any municipal pipeline can be included in the utility tunnel, thereby eradicating phenomena such as "road zippers" and "aerial spider webs" in the urban construction process. As a massive underground structure, the utility tunnel has its own electricity demand. Only by constructing a safe and stable power supply and distribution system inside the pipe gallery can it effectively ensure personal safety and the reliability of pipeline operation.

Weathering the Storm: Planning and Building Smarter

The importance and challenge of utility distribution system strategy and planning cannot be overstated in light of climate change and the increasing frequency of extreme storms. Independent power producers, distributed energy resource (DER) providers, and retail energy providers similarly face the same challenges. The United States witnessed a record‐breaking hurricane season in 2020, resulting in staggering damages of approximately $95 billion. The most recent report from the Intergovernmental Panel on Climate Change (IPCC) highlights the urgency of reducing greenhouse gas (GHG) emissions to limit global warming to mitigate the disastrous and costly effects of climate change. The report indicated that these events are likely to become the norm and will worsen if mitigation and adaptation measures aren't established. These events are becoming more frequent and severe, making it imperative to establish effective mitigation and adaptation measures.

Coordinated Use of Smart Inverters With Legacy Voltage Regulating Devices in Distribution Systems With High Distributed PV Penetration—Increase CVR Energy Savings

This paper studies the coordinated use of smart inverters with legacy voltage regulating devices to help increase the energy savings from conservation voltage reduction (CVR) in distribution systems with high photovoltaic penetration. Two voltage optimization algorithms are developed to evaluate the CVR benefit by considering two types of smart inverter functions: aggregated reactive power control and autonomous volt/VAR control. In each algorithm, smart inverters are coordinately controlled with the operation of legacy voltage regulating devices including load tap changers and capacitor banks. Both algorithms are tested on representative utility distribution system models. Simulation results demonstrate that the proposed algorithms can achieve around 1.8-3.6% energy savings when only using legacy voltage regulating devices and an additional 0.3-0.9% when adding smart inverters.

Enhanced Situational Awareness for DER-Rich Distribution Systems Under Pre- and Post-Outage

Situational awareness (SA) is critical to properly operating active power distribution systems during normal and outage conditions. Appropriate SA tools should provide an accurate estimate of system voltage and current variables, the operational network topology, and the power injections from distributed energy sources (DERs), including behind-the-meter (BTM) photovoltaics (PVs). Obtaining an accurate SA, especially by estimating network topology and gross load demand, is increasingly challenging with the proliferation of BTM DERs with intermittent power generation. Moreover, the SA required for distribution system restoration is even more challenging after a medium to a prolonged outage due to inaccurate estimates of cold load pickup (CLPU) and switch statuses. This paper proposes an integrated real-time model update (RTMU) module for SA enhancement to help distribution system operators (DSOs) understand the power system conditions in dynamic and DER-rich environments. The proposed RTMU consists of several modules to obtain the required level of SA for operational decision-making. It includes estimators for a) BTM PV power, b) network topology, and c) CLPU. The proposed approaches leverage multiple data resources, deep learning approaches, and domain knowledge of the power system to provide the required level of SA to DSOs. The dependencies among these modules are actively leveraged to enhance SA under normal conditions and during power outages. We demonstrate and analyze the performance of the proposed RTMU on a modified IEEE 123-node feeder and a utility distribution system from the Western United States.

Grid Value Analysis of Medium-Voltage Back-to-Back Converter on DER Hosting Enhancement

This paper presents an analysis of the value that can be realized by medium-voltage back-to-back (MVB2B) converters in terms of the increased utilization rate of distributed energy resources (DERs) and the improvement in operational conditions. A systematic, transferrable, and scalable methodology has been designed to analyze and quantify the increased DER value from three perspectives: 1) curtailment reduction of the DER generation, 2) size reduction of the energy storage needed to otherwise realize DER hosting levels, and 3) hosting capacity improvement of the DERs compared to the base distribution circuit capability. In the case study, the proposed methodology is applied to two utility distribution systems for analysis and quantification of the grid value of the MVB2B converter, installed in the distribution circuit, and provided to the solar photovoltaic (PV) DERs. The analysis results demonstrate that the MVB2B converter can deliver significant value to the PV hosting enhancement of two adjacent distribution systems when they are connected by the MVB2B converter. Based on this case study, this paper analyzes and summarizes the approximate realized grid value of the MVB2B converter for distribution systems dominated by different shares of customer classes.

MPC‐based DC microgrid integrated series active power filter for voltage quality improvement in distribution system

SummaryThis paper presents a DC microgrid integrated series active power filter (Se‐APF) to improve the voltage profile of the utility distribution system under sag, swell, and harmonics scenario. The DC microgrid encompasses a solar photovoltaic generation unit and a composite energy storage unit (CESU). A lithium‐ion battery and supercapacitor as a CESU are envisioned in this work. Compared to conventional Se‐APF supported by the capacitor/battery storage, the integrated DC microgrid prolonged the operational features of the Se‐APF for voltage quality improvement and feeding the localized dc loads or charging the CESU occasionally from the PV generation system. Further, a power management algorithm is implemented to coordinate the operations of the sources in the DC microgrid to accomplish the above‐mentioned features. The Se‐APF and associated power converters in the DC microgrid are regulated by a nonlinear controller based on optimal switching vector‐model predictive control algorithm. The proposed control method can be used to help distribution networks with voltage fluctuations by offering much faster and more precise voltage regulation. The feasibility and effectiveness of the proposed control strategy are verified in MATLAB/Simulink platform and then validated in a real‐time simulation platform using Opal‐RT Lab real‐time simulator OP4510.

Power quality improvement by PV integrated UPQC using multi-level inverter with resilient back propagation neural network approach

To increase the life and efficiency of power electronics equipment in a utility distribution system, the power quality improvement is essential part. In this work, to improve power quality by using Robust Resilient Back Propagation Neural Network (RBPNN) scheme for a Photovoltaic (PV)-Integrated Unified Power Quality Conditioner (UPQC) with cascaded multi-level inverter configurations are described. Among the proposed methods, there is no need to use a transformer and filter when multilevel UPQC is applied, and it is one of the great advantages. The proposed UQPC offers a PV array composition with a power converter connected to a DC-link capacitor that can compensate for voltage sag, swell, voltage interruption, harmonics and reactive power. The Robust Resilient Back Propagation Neural Network controller is generate gating pulses to the UPQC. The reference currents and voltages for the controller are estimated using Synchronous Reference Frame (SRF) theory. The proposed cascaded multi-level inverter-based UPQC is designed using Matlab/Simulink Software. The simulation results confirm that the proposed method gives good results compared with existing Adaptive neural Fuzzy Inference System (ANFIS) and fuzzy logic methods. A real-time hardware system is also established to validate the simulation results. The effectiveness of the proposed system RBPN-UPQC approach is compared for both simulation and experimental results gives better low THD level 1.22%.

Impact of Site Conditions and Requirements on Microgrid Design, Control, and Performance

The paper presents the protection design, stability, and control challenges associated with and insights drawn from two real-world microgrids. The presented microgrids were built within the electric utility distribution systems with the existing interconnected electrical loads and Distributed Energy Resources (DERs). Detailed analysis of the observed site protection and stability challenges, supported by an extensive set of site measurements and simulations, along with a systematic approach to troubleshooting the identified issues, is presented. The efficacy of the proposed and or implemented solutions is also discussed.

CVR Study and Active Power Loss Estimation Based on Analytical and ANN Method

Conservation through voltage reduction (CVR) aims to reduce the peak load and energy savings in electric power systems and is being deployed at various utilities. The effectiveness of the CVR program depends on the load characteristics, i.e., the sensitivity of the load to voltage variation, and voltage regulation device settings. In the current literature, there is a lack of discussion on the CVR factor calculation using different measurements, and there is a lack of method for active power loss estimation using substation measurements. This paper provides insights into CVR factor calculation based on the measurements captured at the substation and those at the load location. This paper also proposes a new method based on curve fitting and artificial neural network to estimate the active power loss using input active power, input reactive power and input voltage at the substation. The CVR comparison study conducted in this paper helps in understanding the factors affecting CVR factor and may provide guidance in CVR implementation and impact assessment. The proposed loss estimation method sheds light on the impacts of CVR in terms of load and loss reduction. The results based on simulation studies using the IEEE 13-bus and 34-bus systems are reported in this paper, noting that the proposed methods are applicable to larger systems, as long as the required measurements at the substation are available. Future research includes testing and refining the methods using large IEEE and utility distribution systems and considering the stochastic nature of the CVR factor with changing load and voltage regulator control schemes.

Photovoltaic distributed generation integrated electrical distribution system for development of sustainable energy using reliability assessment indices and levelized cost of electricity

AbstractReliability assessment index is one of the main performance indicator for analyzing the impact of distributed energy generation system in the utility distribution system and minimize the costs associated with energy interruptions. In this study, sustainable energy development by using integrated photovoltaic distributed generation (DG) system considering reliability assessment indices and levelized cost of energy are presented. Electrical transient and analysis program simulation software are used for evaluation and assessment of the reliability indices based on the failure rate, average annual power interruption/outage time and repair time. The analytical method are used to evaluate the expected interruption cost (ECOST) of the system. HelioScope software is a photovoltaic simulation tool are used to design and calculate the energy generation (kWh) as well as global horizontal irradiation (kWh/m2) of the photovoltaic system. Experimental test system is a radial distribution network consisting of an 11.0 kV feeder emanating from 132.0 kV distribution grid station Satiana. According to the reliability evaluation and assessment of experimental test system before integration of photovoltaic distributed energy generation, the average service availability index (ASAI) is 0.9648 per unit. Then, the expected energy not supplied (EENS) is 772.0308 MWh per year and ECOST is 386,652,468.18 PKR per year. After integration of Photovoltaic DG, ASAI is 0.9741 per unit, then the EENS is 563.8584 MWh per year and integration ECOST is 227,087,143.39 PKR per year. The results showed that integrated PV DG system improve the reliability of conventional energy distribution systems.

Forensic Identification and Root Causes of Hot Socket Problems Found in Electrical Meters

Electric meters play a critical role in electric utility distribution systems, especially for residential customers. Because it occurs so infrequently, forensic engineers may not recognize a dangerous condition within these meters known as a “hot socket.” This condition exists where the meter blades make insufficient electrical contact with the socket jaws. This paper reviews methods for forensically examining, diagnosing, and explaining the hot socket phenomenon while exploring smart meters’ incident trends.

A framework to measure the technical, economic, and rate impacts of distributed solar, electric vehicles, and storage

This study explores the joint impacts across the power system of distributed energy resources (DER) that could be deployed in utility distribution systems through an analysis of generation, transmission, and distribution expansion and costs driven by DER adoption. We identify six adoption scenarios that combine deployment levels of rooftop solar photovoltaic modules (PV), electric vehicle charging (EV), and battery storage in residential and commercial customers connected to representative feeders in Indiana by 2025 and 2040. Indiana is a good proxy for many U.S. states with low current DER adoption but potentially high future growth. The economic value of DER is assessed by developing capacity expansion and power flow analysis of the generation and distribution segments, respectively, under future hourly demand assumptions based on each adoption scenarios. Results for the distribution system power flow simulations show that voltage violations are relatively rare. Voltage violations can be mitigated at a very low cost using a combination of smart inverters in future rooftop PV systems and voltage adjustments in the feeder heads. Line loading issues are minimal, with only 0.2% of simulation hours showing loading levels above 100% of capacity. Generation capacity impacts are driven by unmanaged EV charging and could be mitigated with charging management. We estimate that the incremental rate impact from power system investment and operation of increased DER adoption in Indiana will be between −1.6% to + 2% in 2025 and + 0.2% to + 15% in 2040 relative to the base case.

Electric Vehicle Charging System

Electric vehicles are a new and upcoming technology in the transportation and power sector that have many benefits in terms of economic and environmental. This study presents a comprehensive review and evaluation of various types of electric vehicles and its associated equipment in particular battery charger and charging station. A comparison is made on the commercial and prototype electric vehicles in terms of electric range, battery size, charger power and charging time. The various types of charging stations and standards used for charging electric vehicles have been outlined and the impact of electric vehicle charging on utility distribution systems is also discussed. The methodology presented here was time-and cost-effective, as well as scalable to other organizations that own charging stations. Electric vehicles (EVs) are becoming increasingly popular in many countries of the world. EVs are proving more energy efficient and environmental friendly. But the lack of charging stations restricts the wide adoption of EVs in the world. As EV usage grows, more public spaces are installing EV charging stations.

Power factor correction and power quality improvement of supply grid with self-supported transformer-less DSTATCOM for different control strategies

This paper investigates the performance of transformer-less distribution static compensator (DSTATCOM) integrated at the side of the utility distribution system for four different control strategies, viz., unit template (UT) theory, synchronous reference frame (SRF) theory, instantaneous reactive power theory (IRPT) and power balance theory (PBT). The simulation models for the three-phase three-wire power system have been designed to achieve unity power factor with different loading conditions (balanced and unbalanced linear and nonlinear loads). The DC-link is self-supported, i.e., no energy storage element is used but a DC-link capacitor is used only. DSTATCOM fulfils almost all the objectives related to the current related power quality problems created by different types of load. Here, it eliminates the harmonics, compensates reactive power which reduces the burden on the grid, makes the grid power factor unity and eliminates the load unbalances. Here, steady-state and dynamic state analysis has been discussed and comparative results have been presented.

Power factor correction and power quality improvement of supply grid with self-supported transformer-less DSTATCOM for different control strategies

This paper investigates the performance of transformer-less distribution static compensator (DSTATCOM) integrated at the side of the utility distribution system for four different control strategies, viz., unit template (UT) theory, synchronous reference frame (SRF) theory, instantaneous reactive power theory (IRPT) and power balance theory (PBT). The simulation models for the three-phase three-wire power system have been designed to achieve unity power factor with different loading conditions (balanced and unbalanced linear and nonlinear loads). The DC-link is self-supported, i.e., no energy storage element is used but a DC-link capacitor is used only. DSTATCOM fulfils almost all the objectives related to the current related power quality problems created by different types of load. Here, it eliminates the harmonics, compensates reactive power which reduces the burden on the grid, makes the grid power factor unity and eliminates the load unbalances. Here, steady-state and dynamic state analysis has been discussed and comparative results have been presented.

Development of an edutainment shaft garden for integrated waste management in the UGM green campus

Biomass productivity and organic cycles in tropical regions are the highest in the world because of increased temperature, rainfall, humidity, and sunlight year-round. Organic waste not only comes from the agricultural sector (agriculture, horticulture, plantation, forest, livestock, and fisheries), but also from non-agricultural entities (cities, market, offices, households, campuses, industries, and other sectors). Organic waste volume from the integrated campus UGM yard reached 30 tons/day, requiring the support of adequate self-managed waste management facilities. Various experimental approaches were used in designing the Waste Management Centre at UGM as part of an edutainment (education and recreation) program. The problems at the Waste Management Centre included (1) an integrated system of recreational functions in biogas and compost processing; (2) high operational costs; and (3) space efficiency for productivity and processing. Development of a ‘Shaft Garden’ was chosen a solution for (1) creating visual attraction and space experiences from biogas and compost management; (2) utilizing gravitational force as a utility distribution system; and (3) creating a sequence of spaces according to the function. Integrated organic-cycle management by empowering the 9R (Reuse, Reduce, Recycle, Refill, Replace, Repair, Replant, Rebuild, Reward) framework with a multi-function and multi-product approach has provided higher value-addition to environmental, economic, socio-cultural, and health aspects.

An efficient and fast fault recovery algorithm for a resilient grid under extreme events

ABSTRACTFast restoration of power systems is a major concern following a severe outage. Power utilities around the globe aimed at providing reliable and resilient electricity at the consumer end. This paper proposes an efficient and fast fault recovery algorithm for power systems affected by a severe weather condition. The algorithm is developed based on the concept of a proposed recovery index obtained from the resilience curve of the system. The value of the index gives the slope of the resilience curve, which accounts for load restored after the impact of an extreme event. A case study on a typical utility distribution system is conducted to validate the effectiveness of the developed approach. The obtained results are compared with the existing methods reported in the literature. The comparison shows that the performance parameters, viz. computational time and number of switching operations, are least for the proposed algorithm compared to other reported works. The total restoration time for the considered case study has been reduced to 165 h for the proposed optimal fault recovery algorithm from 232 h for the conventional utility approach to completely restore the system back to steady state.

A Three-Level Universal Electric Vehicle Charger Based on Voltage-Oriented Control and Pulse-Width Modulation

Electric vehicles (EVs) could be used to address the issues of environmental pollution and the depletion of non-renewable energy resources. EVs, which are energized by a battery storage system, are becoming attractive because they keep the environment clean. Furthermore, the cost of EVs is becoming cheaper. Thus, EVs will become a significant load on utility distribution system in the future. EV chargers play a significant role in the expansion of EVs. The input current of an EV charger with a high total harmonic distortion (THD) and a high ripple distortion of the output voltage can impact battery life and battery charging time. Furthermore, the high cost and large size of the chargers are considered other issues in EV development. This work presents the complete design process of a universal EV charger with a special focus on its control algorithms. In this regard, a novel control algorithm based on the integration of voltage-oriented control (VOC) and the sinusoidal pulse-width modulation (SPWM) technique is proposed to ensure effective Levels 1, 2, and 3 battery charging. A simulation of the universal EV charger was conducted and assessed in MATLAB–Simulink. Moreover, a laboratory prototype was constructed with a TMS320F28335 digital signal processor (DSP) programmed as the controller to validate its operation and performance. The findings show that the proposed charger is able to provide a controllable and constant charging voltage for a variety of EVs, with an input current of low total harmonic distortion (THD) and an almost unity power factor.

The Relationship Between Leaks, Breaks, and Infiltration

An analysis of leak and break history in a New York utility's distribution system indicates that there most likely is a relationship between water loss from breaks and infiltration into the collection system.

An analysis of enhanced tree trimming effectiveness on reducing power outages

We evaluated the effectiveness of an enhanced tree trimming (ETT) program for its ability to reduce tree-related power outages, and thereby improve resilience, on an electric utility distribution system during storm events. Evaluations encompassed thirteen years of trimming (i.e. 2005–2017) data and were performed for both backbone and lateral utility lines. Backbones included all three phase lines between a substation and a faultable device whereas all other lines were considered laterals. The study site spanned the entire state of Connecticut, where the dominant vegetation is temperate deciduous forest. We controlled for variations in weather, tree cover, and wire type, by pairing ETT-treated zones with nearby untreated zones. ETT-treated conductors had storm outage rates that were 0.07–0.36 outages/km/year lower than untreated conductors or 35–180% lower than the service-area's average annual outage rate for untreated conductors. ETT-treatment was associated with lower outage rates for “minor” outage types (i.e., blown fuse, tripped recloser, etc.) but the treatment effect was not statistically significant for “major” outage types (damaged poles or wires). System-wide ETT application, for the approximately 27,000 km of conductors in the study area, was predicted to reduce annual storm-related outages by an average of 81–104 and 318–759 outages/year for backbone and lateral lines, respectively. Our study provided a robust empirical evaluation of ETT and also proposes a geospatial methodology that controls for variations in weather and environment.