This paper presents a new approach to determine the optimal number and arrangement of power quality monitors (PQMs) for voltage sag detection. It is necessary to determine the optimal number and arrangement of PQMs since their installation at all buses in a network is an uneconomical option due to relatively high price of PQMs. The appropriate mathematical model, that describes the considered optimization problem, is created by using the concept of topological monitor reach area. A new definition of the cost function is presented in the paper in order to simultaneously determine the required number of PQMs and their best arrangement. Also, the effect of setting different values of monitor's coverage control parameter on the obtained results is analyzed. Four optimization methods are implemented to solve the considered problem: Binary Bat Algorithm, Binary Dragonfly Algorithm, Binary Particle Swarm Optimization and Genetic Algorithm. The presented approach is tested on the IEEE 34-node test system. Simulations proved that the Binary Bat Algorithm has the best performance in terms of computational time, convergence and the probability rate of finding the global optimum.

The power system (PS) evolves with the introduction of new technologies in the sectors of production, transmission, distribution and control of electricity consumption. The philosophy of PS control, operation and management is changing. The public low-voltage network (LVN) faces the major changes due to integration of new smart grid technologies. The integration of photovoltaic power plants (PVPPs) and Energy Storage System (ESS) in LVN is a focus of this paper. Three scenarios are considered: (1) analysis of LVN without PVPPs and ESS, (2) analysis of LVN with PVPPs, where LVN is treated as energy storage (ES), (3) analysis of LVN with PVPPs and ESS. The novel algorithm for ESS control aiming to peak load reduction is presented in the paper. Losses and voltage conditions are analyzed on all LVN buses. The slow voltage variations analysis is carried out according to the EN50160 standard. It was shown that the connection of the ESS has negligible impact on losses in LVN. Slow voltage variations are within limits defined by standard EN50160 for all considered scenarios.

This paper describes the transient characteristics and control of the output DC voltage of a stand-alone switched reluctance generator (SRG). A mathematical model of switched reluctance machine (SRM) is developed and implemented in Matlab/Simulink software. The mathematical model is verified experimentally. The robust controller based on the discrete-time sliding mode control (DT-SMC) technique is proposed for the SRG voltage control. The robustness is achieved using the disturbance estimator. The proposed control technique was implemented through simulations on a three phase 12/8-pole SRG with a variable speed and load. The proposed DT-SMC based controller is compared with a standard PI controller. Obtained results show the effectiveness and quality of DT-SMC based voltage control technique for the SRG.

Phasor estimation is an essential task in power system since the voltage angle and voltage RMS determine the available active power and its flow. This paper proposes fast and simple algorithm for harmonic phasor estimation in a three-phase system. Harmonics are considered the most serious power quality (PQ) problem in the emerging scenario with a growing proportion of power electronic based devices in the power system. The algorithm is based on well-known mathematical transform and recommendations given in relevant IEC and IEEE standards. The presented algorithm can be used to generate input data for Harmonic State Estimation.

The paper describes a photovoltaic system (PVS) composed of a group of photovoltaic (PV) panels and presents the initial evaluation of power quality (PQ) in the low-power microgrid connected to these PV panels. This PVS is called solar tree and it is built as a research platform at our faculty to conduct teaching and research on renewable energy sources. The solar tree can operate in two modes: on-grid and off-grid (autonomous operation). An off-grid mode was analysed and experiments were carried out in order to determine the maximum power that can be delivered to the load connected to this autonomous photovoltaic system (APVS). Also, the various consumer's responses to a sudden load changes in this APVS were analysed. The experiments were carried out by using modern power quality monitoring devices and PQ of this single-phase APVS with energy storage is examined in terms of compatibility with the relevant international standards.

This paper describes the transient performance and voltage regulation of a stand-alone self-excited induction generator (SEIG). All characteristics are calculated with a ftux-based mathematical model of the induction machine in the stationary reference frame appropriate for the stand-alone SEIG. The generator model and the control system model are developed using Matlab/Simulink. A presented generator model takes into account significant effects of magnetic saturation on the SEIG performance. The simulation was performed by loading the SEIG with a variable resistive load. Some of the computed characteristics are compared with experimental results. Both uncontrolled and controlled response of the SEIG to load variations were analyzed. It is shown that voltage variations can be reduced by using voltage source inverter and terminal voltage controller.

This paper describes fast analytical model for computation of the switched reluctance machine's (SRM) nonlinear magnetization characteristic and torque lookup table. The flux-tube and the gage-curve methods are used to develop this fast analytical model. Presented model is used for computation of the magnetization characteristic and torque lookup table of three and four-phase SRMs. The simulation results obtained using proposed analytical model are compared to the results of magnetostatic finite-element analysis (FEA) for a three-phase 12/8 SRM. Experimental verification of the analytical model is also presented for the same 12/8 SRM prototype.