Radial Feeder Research Articles

Performance analysis of unbalanced radial feeder for integrating energy storage system with wind generator using inherited competitive swarm optimization algorithm

In recent years, the battery energy storage system (BESS) has been considered as a promising solution for mitigating wind turbine generator intermittencies. In this paper, optimal location and capacity of the BESS with wind power penetrations, and charging/discharging dispatches of BESS are determined using inherited competitive swarm optimization (ICSO) algorithm while improving the performance of the unbalanced distribution network subject to technical constraints. The strategy uses the average load of the feeder as the deciding criterion for charging or discharging the battery. The sustainable average load (SAL) charging method is utilized to charge the battery. The free-running and conservative discharging methods of the battery are studied. The proposed methodology is investigated on IEEE 37 bus unbalanced radial distribution system. The application results show that the proposed methodology enhances various performance objectives of distribution system by optimally coordinating the dispatches of BESS.

Energy Storage Planning for Profitability Maximization by Power Trading and Ancillary Services Participation

One of the main applications of energy storage systems (ESSs) is transmission and distribution systems cost deferral. Further, ESSs are efficient tools for localized reactive power support, peak shaving, and energy arbitrage. This article proposes an ESSs planning algorithm that includes all previous services. The proposed algorithm increases the distribution company profit and minimizes its future system upgrade cost. For a comprehensive planning algorithm, other options, such as including static VAR compensators (SVCs), feeders upgrade, or adding distributed generators, are considered along with ESSs. Different scenarios are utilized to model the load variation, the renewable resources’ intermittency, and the market price fluctuation. The problem constraints include an ESS dynamic model that reflects the capacity and lifetime limitations. Different battery technologies with different costs and dynamic characteristics are compared. The network power flow model is added to account for the voltage level and feeders’ capacity. Power limits constraints are included for the DGs and SVCs as well. The optimization problem is formulated as a mixed-integer quadratic programming problem. To validate the proposed technique, a case study is conducted on a real 41-bus radial feeder in Ontario, Canada using real data for renewable sources, loads, and market prices.

Optimal Design of Grid-Connected Solar Photovoltaic System Using Selective Particle Swarm Optimization

The electricity distribution network in Ethiopia has the radial nature of network configuration. The interruption of power is due to overloading and failure of distribution lines due to external forces, like trees, animals, and wind. The failure of the radial distribution network brings blackout in the whole power system network as there is no alternative electricity supply. The renewable energy potential of Bahir Dar, Ethiopia, especially solar power is abundant and needs a mechanism to give a response for electricity demand in the country and city other than expecting from the national grid. The solar photovoltaic system interconnection in radial feeders may bring a solution for power interruption and network performance. The sizing and siting of the solar photovoltaic system in the Ethiopian radial distribution system required an optimization tool to obtain better distribution network parameter. The power loss minimization and voltage profile enhancement of the radial distribution network are the key objectives of this research. Selective particle swarm optimization (SPSO) is used to fix the size and site of installation for network capacity enhancement. A multiobjective optimization problem is formulated so as to meet different constraints to be optimized by the SPSO. Finally, the SPSO enables determining proper size and site of solar power installation and bringing better performance in the radial distribution network of Ethiopia.

Efficient Operative Cost Reduction in Distribution Grids Considering the Optimal Placement and Sizing of D-STATCOMs Using a Discrete-Continuous VSA

The problem of reactive power compensation in electric distribution networks is addressed in this research paper from the point of view of the combinatorial optimization using a new discrete-continuous version of the vortex search algorithm (DCVSA). To explore and exploit the solution space, a discrete-continuous codification of the solution vector is proposed, where the discrete part determines the nodes where the distribution static compensator (D-STATCOM) will be installed, and the continuous part of the codification determines the optimal sizes of the D-STATCOMs. The main advantage of such codification is that the mixed-integer nonlinear programming model (MINLP) that represents the problem of optimal placement and sizing of the D-STATCOMs in distribution networks only requires a classical power flow method to evaluate the objective function, which implies that it can be implemented in any programming language. The objective function is the total costs of the grid power losses and the annualized investment costs in D-STATCOMs. In addition, to include the impact of the daily load variations, the active and reactive power demand curves are included in the optimization model. Numerical results in two radial test feeders with 33 and 69 buses demonstrate that the proposed DCVSA can solve the MINLP model with best results when compared with the MINLP solvers available in the GAMS software. All the simulations are implemented in MATLAB software using its programming environment.

Power Loss Reduction via Distributed Generation System Injected in a Radial Feeder

The energy demand all over the world is increasing rapidly day by day. In traditional power systems, power plants are located far away from the consumer’s premises. This in turn causes a substantial amount of power loss both in transmission and distribution. In general, distribution system has more losses than the losses occurred on the transmission side. It employs that there will be a significant difference between the generated power and the energy consumers that are (physically) far away from the generating stations. Therefore, the electric utilities always remain under stress due to such non negligible amount of losses which has a direct impact on financial management and efficiency of the power system as well. To address this issue different technique have been introduced to reduce line losses and to improve the efficiency. The best among these techniques is line loss reduction through Distributed Generation (DG) which is more effective than the other techniques. In this paper we have taken three 11kV feeders (located at Bannu) as a case study and for the prescribed technique an attempt has been made to increase the efficiency of a system by integrating different capacity of DG into a radial distribution feeder. The results have been analyzed mathematically, however Electrical Transient Analyzer Program (ETAP) simulator is used as a test bed. Finally, the obtained results are presented in tabular and graphical form in terms of clearly defined parameters.

Power-Flow-Based Secondary Control for Autonomous Droop-Controlled AC Nanogrids With Peer-to-Peer Energy Trading

Regarding the control of micro- and nanogrids, LC- or LCL-filtered power inverters (acting as interfaces with distributed energy resources such as photovoltaic or wind) commonly perform as grid-forming or grid-supporting units to maintain both the frequency and voltage within pre-set standards. Nevertheless, these power inverters are assumed to be connected at the same point of common coupling directly or via radial feeders; thus, the voltage references are the same for each parallel power inverter, thus requiring a virtual impedance loop. In addition, classic power sharing techniques comply with their individual power rates, and circulating currents among distributed generators are not considered. Under these circumstances, energy trading among prosumers and peer-to-peer contracts is not feasible in autonomous AC micro- and nanogrid operations. This paper proposes a reformulated power flow problem, adapted to autonomous droop-controlled AC microgrids, to be used as a secondary control layer. The entire hierarchical control is implemented and experimentally validated in a laboratory-scale nanogrid with energy storage systems, photovoltaic generators and power converters. The obtained results demonstrate the proper performance of the proposed approach, with successful operation of primary and inner controllers.

Photovoltaic Generation Integration with Radial Feeders Using GA and GIS

The electric power generated from different electricity sources are not used efficiently by end users in the world. This is due to the loss of power supplied in the case of electricity transmission and distribution to residential, commercial, and industrial loads. Even if the loss of power in the power system cannot be avoided 100%, it should be reduced to the minimum optimal value. The loss of power in the radial feeders can be minimized using an optimally allocated photovoltaic (PV) generation system by considering the information of geography, solar irradiance of the site, and space availability, which should not have shadow from large buildings and trees. The PV generation system eliminates the problem of power demand by enhancing the capacity of the power network as well as by reducing the depletion and consumption of fossil fuel resources. To reduce power loss and improve system loading capacity for demand response, the integration and finding the optimal place of photovoltaic generation take high concern from power system operators and technicians. The optimal allocation of PV has been done using the Genetic Algorithm (GA) for optimization of a multiobjective function with different constraints. The main objective of this paper is to minimize the power loss of the radial distribution networks by maintaining the phase voltage of the load in balance and improving the drop in voltage along the phase. So, GA is used to determine the best location and capacity of PV generation that can reduce the loss of power in the system. The IEEE-33 bus system is used to test the proposed method. Generally, using the GA and GIS methods results in a high accuracy for optimal placement of PV generation in the IEEE-33 bus radial feeder and enables to reduce the loss of power during transmission and distribution by maintaining the power quality for consumers.

An efficient method to include the effect of radial feeders on optimal coordination of directional overcurrent protections

This short article shows an efficient way to include the effect of coordination with radial feeders on the optimal coordination of directional overcurrent protections. This effect can be important, but it has been seldom considered. The proposed method is based on the inclusion of constraints related to coordination with radial feeders as simple increments of lower limits of the time multiplier settings of upstream directional protections. Although the overcurrent protections of radial feeders usually have inverse-type curves, the fault currents for the coordination are known and, consequently, their operation times can be directly computed. Therefore, these known operation times can be simply summed to the time margin required for selectivity, in order to compute the lower limits of time multiplier settings of upstream directional protections. The main advantage of the proposed method is the avoiding of increments in the number of constraints of the optimization problem.

On the Fairness of PV Curtailment Schemes in Residential Distribution Networks

Active power curtailment of residential PV systems is an effective way to mitigate technical issues in distribution networks. However, existing curtailment schemes can treat households unfairly; e.g., Volt-Watt schemes increasingly being adopted worldwide inherently penalize PV systems at remote locations in radial feeders. Nonetheless, whether fairness is improved or not by alternative curtailment schemes depends on how the impacts on households are considered. In this context, household-centric metrics that quantify PV harvesting, energy export and financial benefit are used along with the Jain’s fairness index to assess fairness from different perspectives. To explore the trade-offs brought by schemes that consider fairness differently, four linearized, three-phase Optimal Power Flow (OPF)-based schemes are proposed to determine, periodically, short-term curtailment settings. Using a real Australian 22kV feeder and realistically modelled LV networks with 4,500+ households, a detailed comparison is carried out considering also a Volt-Watt scheme. Results demonstrate tha tall the schemes that consider fairness are effective in removing locational penalizations. However, in terms of fairness, their performance across the adopted metrics reveals noticeable trade-offs. This highlights the need for decision-makers to determine the metric from which fairness can be based upon in a way that aligns with their respective policies.

Coordinating Demand Response Aggregation With LV Network Operational Constraints

High shares of renewable energy resources are increasing the value of using demand response (DR) mechanisms to enhance the resiliency and efficiency of power system operation. In this context, residential DR is expected to become an increasingly important asset. In order to exploit this resource, DR aggregators are expected to combine the capabilities of a large group of householders and participate, as a single provider, in the electricity market. In doing so, it is imperative for aggregators to consider the operational constraints of the local network. Otherwise, the quality of the electricity service can be jeopardized and the true DR potential overestimated. This paper presents a novel methodology that integrates DR aggregators with distribution network operators for a secure and efficient scheduling and real-time operation of DR in residential radial feeders. The method is evaluated on a real unbalanced feeder where DR provision (from a mix of technologies) is coordinated with the network steady-state thermal and voltage limits. In this study, with the corresponding data seasonality and controllable devices, it is shown that complying with network operational constraints can impose, at certain times, a significant limit to the allocation of DR.

Improvement of the distribution network state estimation with increase of accurate information and using a two-step method

Distribution networks (DNs) are gradually changing and this makes their control and utilization complicated. State estimation (SE) plays a significant role in active distribution networks. The performance of the energy management center in modern distribution networks is highly dependent on the results obtained from the SE. In the present study, considering the shortage of measurements in the DN, a two-step state estimation method with a new network reduction process (NRP) is proposed. In the proposed method, a new NRP is used in a two-step state estimation method to improve the performance of SE in a DN. Obtaining accurate initial information on the network condition improves the performance of SE. The initial SE is performed using a new NRP process to obtain accurate initial data. This information is used as the measurement to improve the performance of secondary SE. This method resolves the shortage of accurate measurements and redundancy measurements, and it improves network SE accuracy without adding any real-time measurement. Moreover, the proposed method is economically affordable. Simulations are performed on the 18-bus UK radial feeder and the IEEE 69-bus distribution network in MATLAB software to guarantee valid operation of the proposed style.

A New Approach for the Setting of Directional Overcurrent Relays by Incorporating Cascading Outages

Directional overcurrent relays (DOCRs) are the essential protective devices in distribution networks which are usually set without considering any contingencies. However, the current challenge in power systems is the existence of uncertainty and its unfavorable consequences. It sometimes appears that some elements simultaneously fail which makes other parts to be overloaded to the extent that it leads to cascading outages. Therefore, DOCRs may have mal-operation which ends in unwanted trips when there is no fault, or they may not operate in the case the fault is located within their reach point. In such cases, the coordination setting will need complex programming with many related non-linear inequality constraints. In this paper, a novel hybrid method is proposed based on multi-objective optimization including new objective functions by using the genetic algorithm (GA). Also, the cascading outages are considered in the presented method based on network data analysis. This approach is performed on distribution part of the IEEE 14-bus meshed system, and a real industrial radial feeder named TOSEE, located in Iran. The simulations have been implemented in MATLAB and PowerFactory-DIgSILENT software packages in different models, and the results are evaluated.

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.

Enhancing radial distribution system performance by optimal placement of DSTATCOM

In this paper, A novel modified optimization method was used to find 
 the optimal location and size for placing distribution Static Compensator in the radial distribution test feeder in order to improve its performance by minimizing the total power losses of the test feeder, enhancing the voltage profile and reducing the costs. The modified grey wolf optimization algorithm is used for the first time to solve this kind of optimization problem. An objective function was developed to study the radial distribution system included total power loss of the system and costs due to power loss in system. The proposed method is applied to two different test distribution feeders (33 bus and 69 bus test systems) using different Dstatcom sizes and the acquired results were analyzed and compared to other recent optimization methods applied to the same test feeders to ensure the effectiveness of 
 the used method and its superiority over other recent optimization mehods. The major findings from obtained results that the applied technique found 
 the most minimized total power loss in system ,the best improved voltage profile and most reduction in costs due power loss compared to other methods
 .

A New Approach for PV Nodes Using an Efficient Backward/Forward Sweep Power Flow Technique

Most of the distribution networks may contain reactive power sources such as distributed generators with reactive support, static VARs compensators or even switching capacitors. In this sense, it is necessary to have an appropriate and convenient model for controlled-voltage (PV) nodes to be applied in power flow distribution networks. On the other hand, the conventional power flow analysis has been an important tool for all power systems engineers. The nonlinear methods based on the Newton- Raphson method and its decoupled forms and the Gauss-Seidel with Ybus factorized method have been popular to nowadays. However, these methods have presented some convergence problems when are applied to distribution networks analysis. The reasons are the inherent characteristics of distribution networks, such as high r/x ratios, very low branch impedances, radial feeder configurations, among others. In this sense, the techniques based on Backward/Forward Sweep (BFS) methods for power flows have been widely applied in distribution systems. However, as above mentioned for controlled-voltage (PV) nodes some challenges in BFS power flow algorithms are presented, some authors have proposed hybrid methods, iterative methods, sensitivities matrix- based methods, among others. Unfortunately, those methods usually require complex formulations and long execution times. In this paper a new approach and easily controlled-voltage (PV) formulation joint with a simple power flows methodology, called LRSV method, is presented. The results show that this no-complex methodology permits to obtain better execution times, responses in a better way for different load, generation and configurations and some tests cases to demonstrate the effectiveness of the proposed methodology.

Use of fitted polynomials for the decentralised estimation of network variables in unbalanced radial LV feeders

The lack of comprehensive monitoring equipment in low voltage (LV) residential feeders, impedes a near-term deployment of centralized schemes for the integration of domestic-scale distributed generation (DG). In this context, this paper introduces a technique that generates a set of fitted polynomials, derived from offline simulations and regression analysis, that characterise the magnitude of representative network variables (i.e. key for network operation) as a direct analytical expression of the controllable local conditions of any DG unit (i.e. active and reactive power injections). Crucially, the coefficients of these polynomials can be estimated, autonomously at the location of each DG unit, without the need for remote monitoring (i.e. using only locally available measurements). During online implementation, the method consists only of direct calculations (i.e. non-iterative), facilitating real-time operation. The accuracy of the polynomials to estimate the magnitude of the network variables is assessed under multiple scenarios on a representative radial LV feeder. Furthermore, the robustness of the method is demonstrated under the presence of new generation and electric vehicles.

Centralized radial feeder protection in electric power distribution using artificial neural networks

Abstract The paper deals with a new way of determining a fault location in an electric power distribution radial feeder using an artificial neural network (ANN) and presents a new centralized protection method based on ANN. The aim of the devised algorithm is to detect the presence of a fault in a radial feeder and to disconnect faulted laterals from the distribution network. The protection schemes that are currently in use cannot leave the whole feeder energized by disconnecting faulted laterals only without even short de-energization of the healthy part of the feeder. A simulation model is also made for training the ANN and for testing the results. Current values for faulty and healthy states are generated by the simulation model and are used as training and testing data for the algorithm. The purpose of the algorithm is to make a decision which feeder circuit breakers should trip. The simulation model and the ANN are modeled by using MATLAB tools. The results show that the tripping of circuit breakers initiated by the algorithm is correct for all states.

Network reconfiguration and optimal allocation of distributed generations for Mayangone distribution system

This paper focuses on reconfiguration of radial distribution system incorporated with optimal allocation of Distributed Generation units (DGs). The network reconfiguration is to optimize the structure of radial feeders by changing the status of normally closed sectionalizing and normally open tie switches. The optimal allocation of DGs in distribution system has to determine the DGs location and their correspondent sizing for enhancing the system effectively. There are many investigations with both two researches either separately or incorporated simultaneously. But network reconfiguration by using Particle Swarm Optimization (PSO) incorporated with optimal allocation of DGs based on Voltage Stability Index (VSI) and analytical approach of Forward Backward Sweep (FBS) method in radial power flow is the novelty of this research. The main objective is to achieve the minimum losses and improvement of voltage profile while all distribution constraints are satisfied. In proposed algorithm, optimal allocation is determined by finding the best sizing and location of DGs based on VSI and FBS load flow, and then PSO reconfiguration finds out the optimal location of tie and sectionalizing switches simultaneously. The study of test system is carried out on Mayangone Distribution System (MDS) and the obtained results are inefficient for this research.

Capacity Enhancement of a Radial Distribution Grid Using Smart Transformer

Distributed generation (DG) and electric vehicle (EV) are increasingly installed in the modern microgrids (MGs). This demands for an improvement in the power handling capacity of the existing distribution feeders. The power handling capacity of a feeder is limited by the voltage magnitude violation caused by overloading. The smart transformer (ST) is proposed as an effective solution for improving the performance of modern MG. This paper utilizes the power management capabilities of the ST with an integrated battery energy storage system (BESS) for improving the power handling capacity of a medium voltage (MV) 5-bus radial feeder. The proposed method demonstrates the ST's capability to control the active and/or reactive power flow at the MV grid for maintaining the steady-state voltage magnitude within the grid-specified limit. A sensitivity analysis based design study is proposed to determine the power rating requirements for different ST and BESS converters during distinct power control scenarios. The analysis shows the capability of ST in injecting/absorbing active and reactive powers in flexible combinations for achieving the desired voltage magnitudes. The findings are verified through simulation and experimental results.