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Distribution network reconfiguration (DNR) is capable to improve indices of power systems by changing the distribution network (DN) topology under normal conditions. Here, DNR is implemented to improve the power quality (PQ) and power losses of DN. Furthermore, to achieve better optimum in DNR, discrete particle swarm optimization (DPSO) algorithm is equipped with a smart radial method. The proposed algorithm is faster than other metaheuristic methods due to the prevention of regeneration non‐radial configurations. In addition, the algorithm increases the probability of finding the optimal configurations using the mutation function. The results clearly demonstrated the positive effect of DNR in improving harmonic losses, total harmonic distortion (THD), and power losses. Furthermore, the proposed method is compared with other metaheuristic algorithms in IEEE 33 bus DN, IEEE 69 bus DN, and real 95‐bus DN in presence of photovoltaic (PV). The results show that the developed algorithm leads to the better or same accuracy and speed in all comparisons. In addition, results indicated that considering the summation of fundamental and harmonic losses compared to only fundamental losses in DNR can lead to further energy saving in DNs. [ABSTRACT FROM AUTHOR]

The growing use of non‐linear loads is one of the main reasons for harmonic distortions in distribution systems. Power quality disturbances have caused improper performance of electrical equipment and have created many technical and economic problems for industries and customers. One approach to overcome these problems and also the correct detection of PQ disturbances is power quality monitoring (PQM). Measurement and estimation are two essential tools to understand and investigate PQ problems in distribution networks. Here, a new estimation model is used to simultaneously extract the fundamental and harmonic phasors information of the system. In other words, the proposed estimation model has been used to access system‐level data. Also, the recursive variational mode extraction (RVME) approach efficiency has been investigated for detecting power quality disturbances (PQDs). Finally, to validate the effectiveness of the proposed PQDs detection method, six different scenarios of disturbances are investigated. The IEEE 13‐bus and IEEE 34‐bus standard distribution test networks are used to evaluate the efficiency of the proposed method. Also, the real‐time PQ disturbances are used for validating the proposed PQDs detection method. Results obtained demonstrate the efficiency and high accuracy of the proposed approach in correctly diagnosing real‐time PQ disturbances. [ABSTRACT FROM AUTHOR]

Hybrid power quality conditioner (HPQC) has been utilised in a co‐phase electrified railway system with the aim of improving power quality indices. A C‐type filter is designed as an auxiliary device alongside the HPQC for high‐order harmonics mitigation in this paper. Alternatively, the C‐type filter compensates a selected portion of load reactive power, while the HPQC compensates for the left required power. Furthermore, the HPQC mitigates grid side unbalance and other harmonics in a co‐phase supplied system simultaneously. In addition, a design procedure of LCL filters is proposed to suppress high‐order harmonic contents induced by the HPQC converters to achieve lower grid‐side total harmonic distortion (THD). Moreover, a flexible partial compensation (PC) method considering the C‐type filter effect on the HPQC performance is adapted to maintain the grid‐side power quality indices in an acceptable range. The C‐type filter and PC method provide VA rating reduction of the HPQC without applying any complication to the compensation control system. Finally, simulation and experimental results are presented to validate the feasibility and functionality of the proposed configuration. [ABSTRACT FROM AUTHOR]

In this study, a coordinated control scheme is proposed for sharing harmonics compensation effort among voltage and current controlled mode (VCM and CCM) inverters in islanded microgrids. In this method, the voltage harmonics compensation of sensitive bus (SB) is achieved by using secondary control as well as virtual impedance and admittance loops in primary control of VCM and CCM units. The limited capacity of the inverter is taken into account for harmonics compensation. Photovoltaic (PV) systems are considered as CCM units. The harmonics compensation is mainly performed by VCM inverters. However, in order to prevent these units from overloading, the PV interfacing inverters (CCM units) are called to collaborate in harmonics compensation whenever needed. The results of simulation study in Matlab/Simulink show the effectiveness of this method in coordination of CCM and VCM units. [ABSTRACT FROM AUTHOR]

AC electrified railway system is a huge single-phase load, which causes significant power quality (PQ) problems to the upstream power grid. Active railway PQ conditioners (ARPQC) have been introduced to overcome the PQ problems. One of the most important complications of the ARPQCs is its high VA rating which entails significant escalation in the price of the conditioner. To mitigate the rating of the ARPQC, a hybrid configuration including an asymmetric balancing traction transformer and a half-bridge railway PQ conditioner (HBRPC) is proposed in this study. The predictive deadbeat current control with low computational burden and fast dynamic response is used to optimise the performance of the HBRPC. Additionally, a PI adaptive gain controller is proposed for DC-link voltage stabilisation, which minimises the negative impact of the voltage control on the current control stage. The feasibility and functionality of the proposed scheme is validated via simulation and experimental results. [ABSTRACT FROM AUTHOR]

This study investigates two common types of stator winding faults in doubly fed induction generators (DFIGs) including inter‐turn short‐circuit fault (ITSCF) and winding resistive asymmetrical fault (WRAF), and compares them with the operation of DFIGs underpower grid voltage unbalance conditions. A complete magnetic equivalent circuit model has been used to model ITSCF and WRAF in the stator windings of DFIG. The aim of this investigation is to discriminate between these types of faults using the rotor‐reference‐voltage signals inside the rotor‐side‐converter control system. A new fault diagnostic index (FDI) is proposed based on normalised energy evaluation of the given signal using the discrete wavelet transform. The accuracy of the proposed FDI has been evaluated by simulation of DFIG performances with Matlab/Simulink software under low number of stator shorted turns conditions, different severities of winding resistive asymmetrical faults, various levels of grid voltage unbalance, various rotor speeds, and various output active powers. Analysis of the simulation results confirms that the proposed FDI can accurately discriminate between ITSCF even with minor shorted turns, WRAF or unbalanced voltages except for the cases with minor asymmetry and healthy conditions of stator winding. [ABSTRACT FROM AUTHOR]

Among harmonic distortion indices presented in International Electrotechnical Commission (IET) standard 61000-4-7, only group total harmonic distortion (THDG) can be used for interharmonic pollution analysis. However, existence of interharmonic components around of fundamental frequency may deteriorate accuracy of this index. To solve this problem, two virtual groups according to IEC standard are defined in this study. Then, two new distortion indices are proposed by using virtual groups in equation of THDG index. The new distortion indices are named as: group and subgroup total harmonic distortion and improved THDG. On the basis of various simulation tests and usage of different waveform decomposition methods, it is shown that proposed indices can better show the amount of waveform distortion caused by interharmonics in respect to IEC indices. [ABSTRACT FROM AUTHOR]