Conventional Distribution Network Research Articles

Analysis of voltage rise phenomena in electrical power network with high concentration of renewable distributed generations

The increasing penetration levels of renewable distributed generation (RDG) into a power system have proven to bring both positive and negative impacts. The occurrence of under voltage at the far end of a conventional electrical distribution network (DN) may not raise concern anymore with RDGs integration into a power system. However, a penetration of RDGs into power system may cause problems such as voltage rise or over-voltage and reverse power flows at the Point of Common Coupling (PCC) between RDG and DN. This research paper presents the impact of voltage rise effect and reverse power flow constraint in power system with high concentration of RDG. The analysis is conducted on a sample DN, i.e., IEEE 13-bus test system, with RDG penetration by considering the most critical scenario such as low power demand in DN and a peak power injection by RDG. For studying the impact of voltage rise and reverse power flow, a mathematical model of a DN integrating RDG is developed. Furthermore, a controller incorporating an advance control-algorithm is proposed to be installed at PCC between DN and RDG to regulate the voltage rise effects and to mitigate the reverse power flow when operating at a worst critical scenario of minimum load and maximum generation from RDG. The proposed control strategy also mitigates the voltage–current harmonic distortions, improves the power factor, and maintain the voltage stability at PCC. The simulations are carried out using MATLAB/Simulink software. Finally, recommendations are provided for the power producers to counteract the effects of voltage rise at PCC. The study has demonstrated that, voltage at PCC can be sustained with a high concentration of RDG during a worst-case scenario without a reverse power flow and voltage rise beyond grid code limits.

Voltage Profile Enhancement and Power Loss Reduction with Economic Feasibility Using Small Capacity Distribution Transformers

Usually, rural areas can be electrified via three-phase distribution transformers with relatively large capacities. In such areas, low voltage lines are used for long distances, which cause power losses and voltage drop for different types of consumers. Reducing losses and improving voltage profiles in rural distribution networks are significant challenges for electricity distribution companies. However different solutions were proposed in the literature to overcome these challenges, most of them face difficulties when applied in the conventional distribution network. To address the above issues, an applicable solution is proposed in this paper by installing a number of small-capacity distribution transformers instead of every single large-capacity transformer in rural areas. The proposed approach is implemented in the branch network of Al-Hoqool village, which belongs to the Nineveh distribution network. The network has been inspected on-site, drawn, and analyzed using the electrical systems analysis program (ETAP). The analysis showed that using the single-phase pole-mounted transformers can improve the voltage in the network’s end by 29% and enhance the voltage profile for all consumers. The analysis has also demonstrated that the modification can reduce the total power losses by 78% compared to the existing network. Concerning the economic aspect, the payback period for the proposed network is assigned to be 20 months.

A Qualitative Comparison of Distance-Based Protection Approaches for Active Distribution Networks

Objective: This paper presents a qualitative comparison of different recently proposed network protection schemes that are based on the distance function. From this comparison, possible opportunities are identified to develop strategies oriented towards protecting active distribution systems. Methodology: This research is carried out in two parts: the first is to identify the fundamental theoretical aspects of distance protection, its main problems, and a description of the most important aspects of the relevant strategies proposed in recent years. The second part consists of selecting aspects and elaborating a qualitative comparison of the different protection schemes analyzed. This comparison makes it possible to establish the advantages and disadvantages of each of the relevant proposals used in conventional electrical networks or active distribution networks. Results: As a result of this research, the most important aspects to consider in the protection design are identified, which therefore strongly affect its performance. These are summarized in a comparative table, which supports future research related to distance protection in active distribution networks. Conclusions: From this research, it can be stated that the solutions analyzed, despite being relevant within the scope of distance protection applied to active distribution networks, have problems to solve. None of these strategies protects the network for all types of failures in a selective, sensitive, reliable, and cost-effective way while guaranteeing minimum supply interruption to consumers. Funding: This paper is a result from projects 6-20-6 funded by Universidad Tecnológica de Pereira and contract 774-2020 (Integra2023) funded by Minciencias, Colombia.

A survey of fault prediction and location methods in electrical energy distribution networks

One of the main factors that disrupt reliability and stop energy provision is the fault occurrence in distribution networks. Thus, accurate and fast fault prediction and location in distribution networks are essential for increasing reliability, fast restoration, optimal electrical energy consumption, and customer satisfaction. This study reviews and investigates fault prediction and fault location topics. To this end, the existing methods and views in the context of fault prediction are reviewed first; then, fault location is investigated. This paper investigates various methods, their advantages, disadvantages, technical reports, and patents in conventional distribution networks, smart-grids, and micro-grids. Comparison of this study with other surveys indicates that it is more comprehensive and despite others covers fault prediction. In addition, it includes an up to date review of the methods for distance measurement and fault location considering different network types (AC/DC), presence of DG, communication and automation standards, synchronous and unsynchronous measurement, magnetic measurement, and state estimation-based fault location methods.

Optimal Allocation and Planning of Distributed Power Generation Resources in a Smart Distribution Network Using the Manta Ray Foraging Optimization Algorithm

In this study, optimal allocation and planning of power generation resources as distributed generation with scheduling capability (DGSC) is presented in a smart environment with the objective of reducing losses and considering enhancing the voltage profile is performed using the manta ray foraging optimization (MRFO) algorithm. The DGSC refers to resources that can be scheduled and their generation can be determined based on network requirements. The main purpose of this study is to schedule and intelligent distribution of the DGSCs in the smart and conventional distribution network to enhance its operation. First, allocation of the DGSCs is done based on weighted coefficient method and then the scheduling of the DGSCs is implemented in the 69-bus distribution network. In this study, the effect of smart network by providing real load in minimizing daily energy losses is compared with the network includes conventional load (estimated load as three-level load). The simulation results cleared that optimal allocation and planning of the DGSCs can be improved the distribution network operation with reducing the power losses and also enhancing the voltage profile. The obtained results confirmed superiority of the MRFO compared with well-known particle swarm optimization (PSO) in the DGSCs allocation. The results also showed that increasing the number of DGSCs reduces more losses and improves more the network voltage profile. The achieved results demonstrated that the energy loss in smart network is less than the network with conventional load. In other words, any error in forecasting load demand leads to non-optimal operating point and more energy losses.

Development of an Industrial IoT Based Monitoring System for Voltage Regulators

The increase in electronic loads connected to electrical network became relevant requirements of the quality of supply. Among the equipment used in the power distribution system stands out regulators medium voltage installed over the grid to maintain voltage levels within indifferent operating range of the oscillations. Therefore, the quality of supply has become a priority and the implementation of technologies that allow transforming conventional electrical distribution networks into intelligent ones is strategic for Distribution Operation Centers (COD) to perform remote interaction with the equipment, in this case, with a power regulator. medium voltage. In this context, this article demonstrates an IoT (Internet of Things) solution for monitoring and controlling medium voltage regulators, through the use of LPWA (Low Power Wide Area) networks, integrating this equipment with the concepts of Smart Grid (SG). The complete development of the project is presented, including the study of the communication protocol DNP3 (Distributed Network Protocol 3), responsible for the exchange of information, between the hardware system and the voltage regulator, the communication system being through the Sigfox and GPRS (General Packet Radio Service), transmitting the regulator data to supervision software. Validation of communication hardware and software with the medium voltage regulator, occurred with bench tests in expressive periods and, after installation in the field, the experiment was validated by reading and recording parameters, such as number of maneuvers, voltage and mains current, obtained directly from the voltage regulator.

An adaptive fault-component-based current differential protection scheme for distribution networks with inverter-based distributed generators

The high penetration of inverter-based distributed generators (IBDGs) T-connected into distribution networks has changed their structure from single-source networks to multi-source multi-branch networks; therefore, conventional distribution network protection schemes are difficult to apply. To this end, a mathematical model of IBDG fault component current considering the control strategy of IBDG is established, and then, a method for estimating the IBDG fault component current using only electrical information at both terminals of the protected line is proposed. On this basis, an adaptive fault-component-based current differential protection scheme suitable for distribution networks with IBDGs is proposed. The proposed scheme only needs to exchange the electrical information at both terminals of the protected line; that is, it can adapt to multiple IBDGs that are T-connected into the distribution networks, reducing the requirements of multi-terminal protection for communication channels and thus lowering costs. Finally, the effectiveness of the proposed protection scheme is demonstrated in the PSCAD/EMTDC software. The results show that the proposed protection scheme is not affected by the location, capacity of the IBDGs, or the fault type and has a high sensitivity.

A novel regression method in forecasting short-term grid electricity load in buildings that were connected to the smart grid

The short- and long-term forecasting of the grid electrical energy of a province or region is important for the management of the conventional electricity transmission and distribution network. Nowadays, the amount of electrical energy, which each residential building has taken from the grid, has gained importance within the scope of smart grids. Residential buildings that take electricity from the smart grid can generate electricity with alternative energy sources such as solar energy. Besides generating its energy these buildings can also take electricity from the electricity grid. In other words, they can use both the energy that they generate and the energy that they receive from the electricity grid. This bi-directional energy flow increases system complexity, and the grid system become more dynamic. Therefore, estimating the electrical load of such a system is also more difficult than the conventional grid system. In this study, the recurrent linear regression method (R-LR), which is based on the linear regression, was proposed. In order to test and validate the proposed approach, the Sundance dataset, which is shared in the U mass trace repository according to smart project was used. To confirm the success of the proposed method, the linear regression (LR), and the extreme learning machine (ELM) methods were used in each of the 59 different datasets. Obtained results, which were applied to 59 different residential buildings smart meter datasets, showed that lower root means square error and corrected symmetric mean absolute percentage error, which was proposed in this paper in order to eliminate zero dividing errors, values were achieved by R-LR compared to LR and ELM. It was found that the proposed R-LR provides better results in modeling dynamic systems and gives good results in forecasting analysis with a time-series dataset.

Advantages and recent advances of smart energy grid

Smart grid is widely recognized technology used to improve the stability and losses of the electric power system. It is encouraging reliability, efficiency, and effective control of the supply of electrical energy. However, it is a hot topic for recent publications and still has a limited understanding among researchers. This review work is to provide insight and support to the beginner researchers since this topic needs a multidisciplinary background knowledge. The conventional electric transmission system and distribution networks struggle to provide resilient performance and reliable service and real-time data. Also, smart grid id a promising network maneuver to stabilize the system once any disturbances break out by using the distributed renewable energy generators, while the conventional networks lack for flexibility to integrate with renewable energy generators or microgrids. This comprehensive work is conducted to map previous controbution in a coherent manar, including the specifications, features, and fundamentals that are presented to benefit the interested readers interested in smart grid development.

Advantages and advances of smart energy grid: A technology review

Smart grid is widely recognized technology used to improve the stability and losses of the electric power system. It is encouraging reliability, efficiency, and effective control of the supply of electrical energy. However, it is a hot topic for recent publications and still has a limited understanding among researchers. This review work is to provide insight and support to the beginner researchers since this topic needs a multidisciplinary background knowledge. The conventional electric transmission system and distribution networks struggle to provide resilient performance and reliable service and real-time data. Also, smart grid id a promising network maneuver to stabilize the system once any disturbances break out by using the distributed renewable energy generators, while the conventional networks lack for flexibility to integrate with renewable energy generators or microgrids. This comprehensive work is conducted to map previous controbution in a coherent manar, including the specifications, features, and fundamentals that are presented to benefit the interested readers interested in smart grid development.

Topology Identification and Line Parameter Estimation for Non-PMU Distribution Network: A Numerical Method

The energy management system becomes increasingly indispensable with the extensive penetration of new players in the distribution networks, such as renewable energy, storage, and controllable load. Also, the operation optimization of the active distribution system requires information on operation state monitoring. Smart measuring equipment enables the topology identification and branch line parameters estimation from a data-driven perspective. Nevertheless, many current methods require the nodal voltage angles measured by phasor measurement units (PMUs), which might be unrealistic for conventional distribution networks. This paper proposes a numerical method to identify the topology and estimate line parameters without the information of voltage angles. We propose a two-step framework: the first step applies a data-driven regression method to provide a preliminary estimation on the topology and line parameter; the second step utilizes a joint data-and-model-driven method, i.e., a specialized Newton-Raphson iteration and power flow equations, to calculate the line parameter, recover voltage angle and further correct the topology. We test the method on IEEE 33 and 123-bus looped networks with load data from 1000 users in Ireland. The results demonstrate that the proposed method can provide an accurate estimation of the topology and line parameters based on limited samples of measurement without voltage angles.

Optimal Chance-Constrained Scheduling of Reconfigurable Microgrids Considering Islanding Operation Constraints

Microgrid concept is one of the suitable strategies for increasing resilience and preventing load curtailment, especially in emergency conditions. Operation in islanded mode is one of the unique features of microgrids that can provide numerous benefits for both consumers and energy producers. Unlike the conventional distribution networks, reconfigurable microgrids enable the reconfiguration process to achieve optimal structure. In this article, a new optimal strategy for scheduling of reconfigurable microgrids considering islanding capability constraints is presented. To demonstrate the successful islanding operation, the islanding capability is considered as a probability of islanding operation (PIO) index which shows the probability, that the microgrid has adequate level of spinning reserve to meet the local load. Taking into account the forecast errors of generated power by renewable energy resources (PV and wind) as well as load demand, the 13-interval approximation is used for the simplification of nonlinearity of PIO. The scheduling of reconfigurable microgrid with islanding operation constraints is formulated as a chance-constrained goal optimization problem, where the objective is defined as minimizing the total operation cost of microgrid in terms of fuel cost, reliability cost, cost of purchasing power from the mains, and switching cost. The proposed method is implemented on a 10-bus radial reconfigurable microgrid test system with photovoltaic (PV) panels, wind turbines, battery, and microturbines, with different levels of PIO. The numerical results show the effectiveness of the proposed scheduling method.

Upgrading Conventional Distribution Networks by Actively Planning Distributed Generation Based on Virtual Microgrids

In addition to active energy management, this article proposes active planning as another critical feature of active distribution networks (ADNs). To develop this set of tasks, this article introduces a three-layer active planning framework consisting of a physical layer, cyber layer, and socioeconomic layer. Furthermore, a three-step developing strategy for ADNs based on a virtual microgrid (VM) is put forward. Then, according to this framework, this article focuses on a specific and fundamental issue that often arises: the optimal allocation of distributed generation (DG). A two-stage scheme based on VMs is a proposed solution. In the first stage, VM boundaries are determined based on the characteristics of a network structure. Using the identified VM boundaries as constraints, a bilevel hierarchical optimization method is applied to determine the optimal DG allocation in the second stage. The proposed method is verified in the popular PG&E 69-bus distribution network.

Impacts of Placement of Wind Turbine Generators on IEEE 13 Node Radial Test Feeder In-Line Transformer Fuse-Fuse Protection Coordination

The ever increasing global demand on the electrical energy has lead to the integration of Distributed Generators (DGs) onto the distribution power systems networks to supplement on the deficiencies on the electrical energy generation capacities. The high penetration levels of DGs on the electrical distribution networks experienced over the past decade calls for the grid operators to periodically and critically asses the impacts brought by the DGs on the distribution network operations. The assessment on the impacts brought by the DGs on the distribution network operations is done by simulating the dynamic response of the network to major disturbances occurring on the network like the faults once the DGs have been connected into it. Connection of Wind Turbine Generators (WTGs) into a conventional electrical energy distribution network has great impacts on the short circuit current levels experienced during a fault and also on the protective devices used in protecting the distribution network equipment namely; the transformers, the overhead distribution lines, the underground cables and the line compensators and the shunt capacitors commonly used/found on the relatively long rural distribution feeders. The main factors which contribute to the impacts brought by the WTGs integration onto a conventional distribution network are: The location of interconnecting the WTG/s into the distribution feeder; The size/s of the WTG/s in terms of their electrical wattage penetrating the distribution network; And the type of the WTG interfacing technology used labeled/classified as, Type I, Type II, Type III and Type IV WTGs. Even though transformers are the simplest and the most reliable devices in an electrical power system, transformer failures can occur due to internal or external conditions that make the transformer incapable of performing its proper functions. Appropriate transformer protection should be used with the objectives of protecting the electrical power system in case of a transformer failure and also to protect the transformer itself from the power system disturbances like the faults. This paper was to investigate the effects of integrating WTGs on a distribution transformer Fuse-Fuse conventional protection coordination scheme. The radial distribution feeder studied was the IEEE 13 node radial test feeder and it was simulated using the Electrical Transient Analysis Program (ETAP) software for distribution transformer Fuse-Fuse protection coordination analysis. The IEEE 13 Node radial test feeder In-line transformer studied is a three-phase step down transformer having a star solidly grounded primary winding supplied at and a star solidly grounded secondary winding feeding power at a voltage of . The increase on the short circuit currents at the In-line transformer nodes due to the WTG integration continuously reduces the time coordination margins between the upstream fuse F633 and the downstream fuse F634 used to protect the transformer.

Impacts of Placement of Wind Turbine Generators on IEEE 13 Node Radial Test Feeder In-Line Transformer Fuse-Fuse Protection Coordination

The ever increasing global demand on the electrical energy has lead to the integration of Distributed Generators (DGs) onto the distribution power systems networks to supplement on the deficiencies on the electrical energy generation capacities. The high penetration levels of DGs on the electrical distribution networks experienced over the past decade calls for the grid operators to periodically and critically asses the impacts brought by the DGs on the distribution network operations. The assessment on the impacts brought by the DGs on the distribution network operations is done by simulating the dynamic response of the network to major disturbances occurring on the network like the faults once the DGs have been connected into it. Connection of Wind Turbine Generators (WTGs) into a conventional electrical energy distribution network has great impacts on the short circuit current levels experienced during a fault and also on the protective devices used in protecting the distribution network equipment namely; the transformers, the overhead distribution lines, the underground cables and the line compensators and the shunt capacitors commonly used/found on the relatively long rural distribution feeders. The main factors which contribute to the impacts brought by the WTGs integration onto a conventional distribution network are: The location of interconnecting the WTG/s into the distribution feeder; The size/s of the WTG/s in terms of their electrical wattage penetrating the distribution network; And the type of the WTG interfacing technology used labeled/classified as, Type I, Type II, Type III and Type IV WTGs. Even though transformers are the simplest and the most reliable devices in an electrical power system, transformer failures can occur due to internal or external conditions that make the transformer incapable of performing its proper functions. Appropriate transformer protection should be used with the objectives of protecting the electrical power system in case of a transformer failure and also to protect the transformer itself from the power system disturbances like the faults. This paper was to investigate the effects of integrating WTGs on a distribution transformer Fuse-Fuse conventional protection coordination scheme. The radial distribution feeder studied was the IEEE 13 node radial test feeder and it was simulated using the Electrical Transient Analysis Program (ETAP) software for distribution transformer Fuse-Fuse protection coordination analysis. The IEEE 13 Node radial test feeder In-line transformer studied is a three-phase step down transformer having a star solidly grounded primary winding supplied at and a star solidly grounded secondary winding feeding power at a voltage of . The increase on the short circuit currents at the In-line transformer nodes due to the WTG integration continuously reduces the time coordination margins between the upstream fuse F633 and the downstream fuse F634 used to protect the transformer.

Planning optimization and stochastic analysis of RE-DGs for techno-economic benefit maximization in distribution networks

In practical distribution networks of long-distance feeders, load's expansion and seasonal load variations seriously affect the system performance. In the context of the present advancements in D.G.s, especially generating from the renewable energy (RE) sources along with the recent support of policy-makers, it is smart consideration to transform the long-distance conventional distribution networks into the optimal DG-integrated systems for the augmentation of the technical and economic benefits jointly. In this article, a novel methodology, namely Hybrid-PPSO-GSA, is proposed and applied to maximize the techno-economic benefits via an optimal RE-DG integrated system. The proposed methodology focused on the optimal placement and sizing of RE-DG into the distribution system, considering the stochastic analysis of RE-DGs such as W.T. and P.V. with multiple objectives. The Hybrid PPSO-GSA was tested on standard 69-bus systems and particularly implemented on 94-bus long-distance practical distribution feeder located in Portuguese; for power loss reduction, voltage profile, and stability enhancement. Apart from the reduction in the power loss and voltage improvement, the energy loss can be improved jointly, resulting in the coupled techno-economic contribution of the DG-integrated system. Simulations are conducted for various scenarios, and the obtained results demonstrate the merits of the proposed scheme.

Multi‐slack power flow for islanded microgrids with radial and meshed topologies

This study proposes a new power flow formulation for islanded microgrids. The proposed power flow is based on the effect of the superposition principle and the solution of a small non-linear subproblem to determine the frequency of the microgrid and the voltage magnitude in the angular reference node in each iteration. These variables are determined by considering the following equations in the non-linear subproblem: active and reactive power balance equations and specified phase at the angular reference node. The application of the superposition principle allowed to obtain two versions of the proposed technique: one for radial networks - based on the current summation method - and another for meshed networks - based on the Gauss-Zbus method. Therefore, the iterative framework prosed in this study expands in a simple and integrated way the two most commonly used power flow methods in conventional distribution networks for islanded microgrids. The tests in microgrids with 33, 310 and 1438 nodes showed that the proposed approach has the same accuracy as Newton-Raphson algorithm, but with significantly lower computational cost in large scale microgrids. In addition, the proposed method for island microgrid showed good accuracy and convergence for the most common load models applied in power flow studies of islanded microgrids.

Model-Free Energy Management System for Hybrid Alternating Current/Direct Current Microgrids

A hybrid ac/dc microgrid combines the benefits of ac and dc power systems. It provides high efficiency and is compatible with conventional ac distribution network. This article proposes a centralized energy management approach to perform coordinated control on a hybrid ac/dc microgrid as a single-controllable entity. The central controller relies on low-bandwidth communication channels and is aimed at achieving 1) proportional power sharing among energy storage units located in both dc and ac sides of the microgrid, 2) state-of-charge equalization of the energy storage units, 3) grid power flow control, 4) plug-and-play capability, and 5) operation in grid-connected and islanded modes through an interlinking utility interface converter. The state-of-charge equalization method guarantees uniform operation of the energy storage units during both charge and discharge modes considering typical operational transients. Finally, the proposed model-free approach is evaluated experimentally through a laboratory-scale hybrid ac/dc microgrid in different operational conditions in both grid-connected and islanded operating modes.

Active distribution system state estimation incorporating photovoltaic generation system model

The inherently intermittent and varying power generation of distributed energy resources (DER) makes the situational awareness of active distribution systems (ADS) a challenging issue. Considering the detailed photovoltaic (PV) system model and environmental influencing factors including solar irradiance and temperature, this paper develops a state estimation model for the ADS with integrated PV power generation systems. Firstly, in order to achieve high computational efficiency, an explicit function fitting model of PV arrays is proposed and used to accurately approximate the conventional five-parameter model. Then, the state variables of a PV generation system are selected, and the measurement equations and the Jocobian matrix are derived. Finally, combined with the conventional distribution network model, state estimation and bad data processing of an ADS with PV systems are realized. A generalized per unit system is also developed for unified standardization of electrical and non-electrical quantities. Simulation results in the IEEE 33-bus system show that the proposed model significantly expands the scopes and capabilities of state estimation and bad data processing in ADSs, which facilitates comprehensive and reliable monitoring of ADSs.

Probabilistic framework for transient stability contingency ranking of power grids with active distribution networks: application in post disturbance security assessment

The conventional distribution network is becoming an active grid due to widespread integration of distributed energy resources (DERs). This integration raises great concerns about security of the power system considering the growing interactions between the transmission and active distribution systems. One way to ensure stability of the integrated power system is prediction of critical contingencies which can jeopardize the power system security. Therefore, this paper aims to investigate transient stability contingency ranking in power grids considering the uncertainties raised by DERs of active distribution networks. To this end, probabilistic transient stability prediction framework is provided, in which the probability density function of transient stability condition is calculated based on the normalized stability indicators. The normalized stability indicators are based on the rotor angle and rotor speed. The normalized stability indicators are only utilized in the case of using fault data for prediction. Based on the proposed scheme, the instability of generators is anticipated through the proposed probabilistic transient stability prediction framework. Also, the effects of the probable topology changes on the line overload and also the voltage profile are investigated. Finally, the performance of the proposed method is validated and compared with the time domain simulation under various operating conditions.