مجله کیفیت و بهره وری صنعت برق ایران
سال نهم شماره 3 (پیاپی 20، پاییز 1399)

In this paper, a distributed method for reactive power management in a distribution system has been presented. The proposed method focuses on the voltage rise where the distribution systems are equipped with a considerable number of photovoltaic units. This paper proposes the alternating direction method of multipliers (ADMMs) approach for solving the optimal voltage control problem in a distributed manner in a distribution system with high penetration of PVs. Also, the proposed method uses a clustering approach to divide the network into partitions based on the coupling degrees among different node. The optimal reactive power control strategy is conducted in each partition and integrated using ADMM. The proposed method is tested on a real distribution test system. The result evidence that the proposed method has used the lower reactive power if compared to the conventional method.

This paper proposes a new hybrid active power filter, including voltage source converter (VSC) based active power filter and Thyristor Controllable LC Passive Filter (TCLC-HAPF) for eliminating harmonic load current components and compensating reactive power. This new structure which is based on the separation of high and low-frequency components of load current idea can reduce the drawbacks of both active and TCLC based filters. Low-frequency components of the load current applied to the active power filter and high orders are applied to the controllable thyristor passive filter (TCLC). The DC voltage minimization strategy which is based on DC voltage calculation in the fundamental and harmonic frequencies has been used for reducing the power losses and overall cost. The proposed structure is not only able to keep the network power factor more than 0.9 but also maintain the network current THD at %4.8 under the worst case of the load operation, which both satisfy the IEEE519-2014 standard. Also, the operation of the proposed hybrid filter at a minimum DC voltage reduces switching losses. This strategy has less computational burden compares to the traditional methods. The proposed idea reduces the THD of network current and satisfy the IEEE519-2014 standard and also enhance the power factor. To validate the operation of the proposed Hybrid Active Power Filter a part of the sample power network has been simulated and studied by using PSCAD / EMTDC software.

Power system protection at transmission and distribution levels based on overcurrent relays is essential based on their properties such as detection, stability, high speed, backup and error correction accuracy. Since distributed generation sources are connected to the power grid, they not only increase the short circuit level of the grid, but also disrupt the set point of main and backup relays, which will interrupt the healthy areas of the grid. In order to maintain the safety and stability of the network and to avoid increasing the power rating of the existing equipment, Superconducting Fault Current Limiter (SFCL) devices are utilized to significantly reduce the short circuit current at its primary cycles. However using of SFCLs, may lead to inadequate relay performance and lack of short circuit current detection. In order to solve the above problems, this paper presents a SFCL model with resistive structure and coupling inductance, while increasing the fault impedance path and reducing short circuit current, optimally. Then shielding synchronization between main relays and their near and far back-ups are achieved. Finally proposed objective function is minimized using the improved particle swarm optimization algorithm and three case studies will be performed. The simulation results represent the superiority of the proposed method in resolving the error and eliminating disturbance between the relays at the shortest possible time.

In recent years, electric vehicles have attracted significant attention due to environmental issues. Charging stations installation requires a systematic consideration of relevant issues such as determination of the location and size of charging stations. On the other hand, it is necessary to encourage private investors to invest in charging stations installations and to provide proper conditions for them so that they can profit from their investment. In this paper, the fast charging station (FCS) planning problem is modeled as a mixed integer nonlinear programming (MINLP), in which the objective function of distribution company (DISCO) and FCS owner (FCSO) have been considered, separately. In the proposed model, the location and size of FCSs as well as the price of transacted energy between DISCO and FCSO are determined, such that the objective functions of DISCO and FCSO are optimized. In the proposed method, queuing theory and user equilibrium based traffic assignment model are used to determine the size of FCSs. Then, the problem of multi-objective planning of FCSs has been investigated, considering the objectives of DISCO and FCSO. In addition, the final solution is chosen from the Pareto front solutions based on the economic and operational indices. Finally, the efficiency of the proposed method is demonstrated by numerical results.

Demand-side management is one of the ways to create interaction between the microgrid and increase consumer participation in management schemes. Different algorithms and strategies have been used to execute consumption management programs that often covering a limited number of loads in several specific types. In this paper, first, the load shift method as an optimization problem to reduce system demand peak and subscriber bills for various loads in smart microgrid is solved by (H-PSO-SCAC) algorithm, then the effect of the proposed program on the generation and presence of microgrid in market for improving the level of social welfare is aimed. The results are performed on a smart grid consisting of three Residential, commercial and industrial microgrids that including different types of controllable loads. The results show that the proposed program can reduce peak load, reduce subscriber bills, save production costs, help balance supply and demand, and improve the level of social welfare from the perspective of the distribution system operator.

One of the most important tasks of operators in distribution companies is to restoration after a fault in the network. In load restoration schemes, in addition to observing the load flow constraints, it is necessary to maintain the grid structure radially and, most importantly, observing the balance of consumption with the possibility of providing load due to the limitations of the backup feeder (or distributed resource constraints). This paper presents a new approach called smart load shedding in distribution networks, which aims to design a smart load shedding module in situations where it is not possible to provide load after a network failure. In this case, the network load restoration will be provided at the lowest outage cost and in the shortest possible time to maximize customer satisfaction. In order to validate the proposed method, the level of automation of the sample distribution network for smart control of loads is defined in three scenarios. The types of loads available in smart homes are also prioritized and categorized into three categories of adjustable, interruptible, and shiftable loads. The proposed method is coded in the MATLAB software environment. To demonstrate the effectiveness of the proposed model, simulation is implemented on an RBTS system. The results show the effectiveness of the proposed method in reducing costs and improving the restoration management of the distribution system.