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This paper presents the optimal scheduling of active distribution network (ADN) with linear and non‐linear loads in the presence of an integrated unit of electric spring and electric vehicle parking lot (IUEE). The proposed scheme is formulated in the form of three‐objective optimization, which minimizes the expected operating cost of the ADN, voltage deviation function (VDF), and the total harmonic distortion (THD) of the voltage in separate objective functions. Constraints include harmonic power flow (HPA) equations, operation and power quality limits, and operation model of the IUEE. This scheme has uncertainties of load, energy price, and energy demand of EVs, which are modelled here using stochastic programming. Next, the sum of the weighted functions method as a subset of the Pareto optimization technique is adopted to extract the integrated single‐objective problem. Then, Sine‐Cosine Combined Algorithm (SCA) and Gray Wolf Optimization (GWO) are used to achieve an optimal solution. In the end, by examining the numerical results obtained from the implementation of the proposed scheme on a 69‐bus ADN, the capability of the design in enhancing the economic situation, operation, and power quality of the ADN compared to network power flow studies obtained by optimal scheduling of the IUEE is confirmed. [ABSTRACT FROM AUTHOR]

An accurate inter‐circuit fault location algorithm for double‐circuit transmission lines compensated by a generalized unified power flow controller based on phasor analysis is presented. The proposed algorithm utilizes synchronous currents and voltages of the buses on both sides of the line to accurately calculate the fault location. Using the equations of sequence component circuits, the algorithm calculates voltage and current of the fault point on both circuits. Then, using boundary conditions equations for 98 types of inter‐circuit fault on the double‐circuit transmission lines, the accurate location of the fault is obtained. The number of boundary conditions equations varies depending on the type of faulty phases of the two circuits and the number of unknowns in the current and voltage equations of the fault point. The calculation of these boundary equations are also described. The results presented in the simulation section verify the validity and accurate performance of the proposed algorithm under different fault conditions. [ABSTRACT FROM AUTHOR]

Network reconfiguration (NR) has undergone new changes to adapt to smart grid evolution. Internet of things (IoT) has found its way to smart grids especially in the distribution systems. Demand‐side management can be more efficient in the presence of IoT. IoT‐based energy management systems can have bidirectional communication with smart grids and decide according to their preferences, time‐of‐use (TOU) pricing, and their flexible devices. Therefore, customers would consume electricity more interactively. Consequently, the total load profile will be changed and a new NR approach must be adopted to meet load demands. So, the selection of critical switches must be modified to achieve the most effective network resource utilisation. For this purpose, a mixed‐integer linear programming model for feeder reconfiguration is presented considering the customers' behaviours in the IoT environment. At first, the customer manner is investigated at different prices and preferences. Then the total load profile is calculated considering the normal distribution of uncertain customer preference factors. Finally, the identification of critical switches is obtained using the proposed method. The optimisation is done in YALMIP and MOSEK toolboxes. Results show the effectiveness of the proposed method to efficient utilisation of IoT potentials and renewable energy benefits. [ABSTRACT FROM AUTHOR]

In this paper, a bi‐level power management strategy is presented for an active distribution network (ADN) in the presence of virtual power plant (VPP). In the proposed strategy, VPP contains renewable energy source (RES), energy storage system (ESS) and electric vehicles (EVs) parking lot coordinated with VPP operator (VPPO), and there is a coordinated framework between VPPO and distribution system operator. The proposed power management strategy (PMS) is considered in the context of the bi‐level optimization problem. In the first level, the optimal harmonic power flow formulation of the ADN is considered by minimizing the summation of energy cost, voltage deviation function and voltage THD% as a normalized objective function. In the second level, the VPP is modeled according to the framework of day‐ahead energy and ancillary services markets. In the next step, the linear format of the proposed non‐linear original problem is obtained with an optimal solution and low calculation burden. Also, the Karush‐Kuhn‐Tucker condition is used to convert the proposed bi‐level PMS approach to a single‐level model, and the scenariobased stochastic programming models the uncertainty of load, energy price, RES power, and EVs demand. Finally, the proposed strategy is applied on the 33‐bus distribution network using GAMS software. [ABSTRACT FROM AUTHOR]

In this study, on the basis of a new agent‐based situational awareness platform, the amount of severity in closeness to voltage instability occurrence is determined. In the proposed platform (with the aid of the agents of the disturbance detection unit that are responsible for perception of environmental events and understanding the current situation and the agents of the early enough instability prediction unit that predicts instability occurrence), the novelty is in creating the agents of clustering units that are responsible for prediction of the future status, i.e. severity in closeness to voltage instability occurrence through determining the severity class. This clustering unit maps the reactive power‐based features obtained from unconstrained power flow analyses, to the instability time; without any need of post‐disturbance data, i.e. the method belongs to just‐after‐disturbance algorithms. Then, it estimates the severity of the closeness to instability for any test scenario according to its membership degree related to the pre‐defined severity clusters. The simulation results show acceptable overall accuracy (up to 99%) in performing early warning task for operators of power systems. [ABSTRACT FROM AUTHOR]

In this study, a simple, fast, and adaptive network reduction procedure is presented for long‐term voltage stability analyses, to speed up the simulation time. The proposed procedure consists of two parts including disturbance detection based on data from synchronised measurement devices; and the rest, up to the final estimated values, based on simulations and calculations. In turn, simulations and calculations result in an adaptive dynamic‐oriented determination of external sub‐network (according to the disturbance occurred) and substituting an appropriate equivalent for that subsystem. The external subsystem is determined without any need to measure post‐disturbance data, while the detection criteria are calculated by simulations at 0.8 s after disturbance occurrence. The results have shown considerable reduction in the simulation time while providing acceptable accuracy in delivering the time of voltage instability occurrences, especially when applying the proposed error compensation procedure. [ABSTRACT FROM AUTHOR]

In this study, the proposed algorithm is a help for utilities to find out when voltage instability will happen, as soon as they realise that a disturbance may/will result in voltage instability. In this regard, the data gathered, on‐line, by a wide area monitoring system (WAMS) is supposed to be processed in an energy management system, where, finally, voltage instability inception time will be determined. The proposed algorithm employs k‐nearest neighbour algorithm as an instance‐based learning algorithm. This estimation uses only pre‐disturbance information and exact disturbance data, so it is fast enough for real‐time applications. A comprehensive investigation of the input features has resulted in introducing the most appropriate feature set and the most effective search procedure in estimating the instability time. The simulation results show an acceptable accuracy in estimation of voltage instability time. [ABSTRACT FROM AUTHOR]

An ultra‐high‐speed, accurate and reliable algorithm is proposed in this study for the identification and faulted phases selection of inter‐circuit faults. For this purpose, modal components of current samples just before they arrive to the relay location are extracted. Teager energy operator is used here for the extraction of current travelling waves (TWs). The amplitude of the TWs in different modal components and their ratios in similar modal components are used for the inter‐circuit fault identification and finding the faulted phases. Test signals are simulated in PSCAD/EMTDC software and the algorithm is implemented in MATLAB. Results show that the proposed algorithm is a really ultra‐high‐speed algorithm which can be reliably used for the identification and classification of the inter‐circuit faults. [ABSTRACT FROM AUTHOR]

This study proposes an intelligent traveling‐wave (TW)‐based protection algorithm for parallel transmission lines. In the proposed algorithm, Karenbauer's phase to modal transform is applied on three phase current signals. Teager energy operator is then applied on the modal components to extract TWs. First extracted TW of each modal component along with well‐designed fuzzy systems are used for internal fault identification and fault type classification. In order to find the fault location, the time difference between the first and the second TWs and the TW propagation speed are utilised. Test signals are generated in PSCAD/EMTDC software and the algorithm is implemented in MATLAB. Results show that the proposed algorithm is an ultra‐high‐speed algorithm for the reliable protection of parallel transmission lines. [ABSTRACT FROM AUTHOR]

This study presents a new voltage control algorithm for multilevel inverters which are used to connect the distributed generation (DG) sources (like photovoltaic cells) to the network, which is called the voltage look-up table method (VLUTM). This method can build up an almost sinusoidal voltage at the inverter output with the least number of switching in the power circuit, and the best possible harmonic spectrum without the need to any big filtering. On the other hand, in some specific applications where the DG has been set up beside a non-linear load, VLUTM can make a reference voltage based on the reference current to take a desired current form the DG. This way the DG can compensate the major low-order load current harmonics and improve the source side current THD greatly. Decreasing the switching frequency as much as possible, which leads to better efficiency and less EMI problems, the capability of implementation both in single phase and three phase circuitry, and the very simple and desired current control, would be the major benefits of this method. The simulation results taken from Matlab/Simulink and the experimental results on a 1 kVA experimental prototype are presented to evaluate the performance of this method. [ABSTRACT FROM AUTHOR]

There are many types of distributed-generation (DG) sources that cannot be connected to the network directly and use an inverter-based interface. In harmonic compensators [like active power filters (APFs)], the coupling transformer disrupts the compensation capability, therefore the transformerless inverter schemes have grown up in recent years. A new cascaded multilevel transformerless inverter topology is introduced in this study to connect the DG sources to power utility. The proposed circuit of this study can compensate the current harmonic of the non-linear load (as in APF) and inject maximum possible active power as a DG source interface, simultaneously. A fixed gain called KC is obtained based on the load nature, and is used to adjust the set point of the inverter between two operating modes. Proposed scheme has been simulated in Matlab/Simulink to evaluate the circuit performance both in the maximum active power injection mode and the load harmonic compensation mode. Then a 2.2 kW single-phase prototype of the circuit is used for experimental evaluation of the study. Both simulative and experimental results prove that such a circuit minimises the total harmonic distortion of the source side current to an acceptable margin, while injecting the maximum possible active power. [ABSTRACT FROM AUTHOR]