Implementation of solar photovoltaic array and battery powered enhanced DC-DC converter using B4-inverter fed brushless DC motor drive system for agricultural water pumping applications

The proposed research involves, an implementation of solar photovoltaic array and battery powered enhanced dc-dc converter using B4-inverter fed brushless dc motor drive system for agricultural water pumping applications. It consists of step up and step-down converter, DC-link module. DC-link switching is achieved by reduced ripple voltage which results in improved quality of obtained output power. The Three Port Converter has been proposed and operated in unidirectional and/or bidirectional way simultaneously, for achieving an inherent dual voltage and power flow control. Switch count makes the system more cost effective. An excellent tracking performance under dynamic condition with negligible oscillations around optimum operating point is achieved. Optimally selecting the initial value of duty ratio and its perturbation size offer soft starting of BLDC motor by slowly increasing the DC-link voltage of VSI. A simulation model of solar photovoltaic array and battery powered enhanced DC-DC converter is developed and its performance is analysed for various operating conditions

Optimizing the Dynamic Performance of a Wind Driven Standalone DFIG Using an Advanced Control Algorithm

The article seeks to improve the dynamic performance of a standalone doubly fed induction generator (DFIG) which driven by a wind turbine, with the help of an effective control approach. The superiority of the designed predictive controller can be confirmed through evaluating the performance of the DFIG under other control algorithm, which is the model predictive direct torque control (MPDTC), model predictive current control (MPCC) as classic types of control. Firstly, the operating principles of the two controllers are described in details. After that, a comprehensive comparison is performed among the dynamic performances of the designed MPDTC, MPCC techniques and the predictive control strategy, so we can easily present the merits and deficiencies of each control scheme to be able to easily select the most appropriate algorithm to be utilized with the DFIG. The comparison is carried out in terms of system simplicity, dynamic response, ripples’ content, number of performed commutations and total harmonic distortion (THD). The results of the comparison prove the effectiveness and validation of our proposed predictive controller; as it achieves the system simplicity, its dynamic response is faster than that of MPDTC and MPCC, it presents a lower content of ripples compared to MPDTC and MPCC. Moreover, it can minimize the computational burden, remarkably. Furthermore, the numerical results are showing a marked reduction in the THD with a percentage of 2.23 % compared to MPDTC and 1.8 % compared to MPCC. For these reasons, it can be said that the formulated controller is the most convenient to be used with the DFIG to achieve the best dynamic performance

Low-head pumped hydro storage: A review of applicable technologies for design, grid integration, control and modelling

To counteract a potential reduction in grid stability caused by a rapidly growing share of intermittent renewable energy sources within our electrical grids, large scale deployment of energy storage will become indispensable. Pumped hydro storage is widely regarded as the most cost-effective option for this. However, its application is traditionally limited to certain topographic features. Expanding its operating range to lowhead scenarios could unlock the potential of widespread deployment in regions where so far it has not yet been feasible. This review aims at giving a multi-disciplinary insight on technologies that are applicable for low-head (2-30 m) pumped hydro storage, in terms of design, grid integration, control, and modelling. A general overview and the historical development of pumped hydro storage are presented and trends for further innovation and a shift towards application in low-head scenarios are identified. Key drivers for future deployment and the technological and economic challenges to do so are discussed. Based on these challenges, technologies in the field of pumped hydro storage are reviewed and specifically analysed regarding their fitness for low-head application. This is done for pump and turbine design and configuration, electric machines and control, as well as modelling. Further aspects regarding grid integration are discussed. Among conventional machines, it is found that, for high-flow low-head application, axial flow pump-turbines with variable speed drives are the most suitable. Machines such as Archimedes screws, counter-rotating and rotary positive displacement reversible pump-turbines have potential to emerge as innovative solutions. Coupled axial flux permanent magnet synchronous motor-generators are the most promising electric machines. To ensure grid stability, grid-forming control alongside bulk energy storage with capabilities of providing synthetic inertia next to other ancillary services are required

Design aspects of high performance synchronous reluctance machines with and without permanent magnets

Recently, a growing interest in the efficiency and the cost of electrical machines has been observed. The efficiency of electric motors is important because electric motors consume about 40%-45% of the produced electricity worldwide and about 70% of the industrial electricity1. Therefore, some types of electric motors have been classified in proposed standard classes1 based on their efficiency. By consequence, efficient and low cost electric motors are necessary on the market. Several types of electric motors are used in industrial applications such as permanent magnet synchronous motors (PMSMs), induction motors (IMs) and reluctance motors (RMs). Due to the high cost of PMSMs and due to the rotor losses of the IMs, the RMs can be considered as promising and attractive candidates. Moreover, they have a robust and simple structure, and a low cost as there are no cage, windings and magnets in the rotor. There are two main types of RMs: switched reluctance motors (SRMs) and synchronous reluctance motors (SynRMs). However, there are some disadvantages of these types of machines. On the one hand, the SRMs have problems of torque ripple, vibrations and noise. In addition, their control is more complicated than that of three-phase conventional motor drives, a.o. because of the high non-linearity of the inductance. On the other hand, the SynRMs have a low power factor, so that an inverter with a high Volt-Ampère rating is required to produce a given motor output power. Therefore, adding a proper amount of low cost permanent magnet (PM) material - such as ferrite - may be a good option to boost the power factor. The PMs also increase the efficiency and torque density. These types of motors are ---------------------------------------------------------------------------------------------------------------------- 1Waide, P. and C. Brunner (2011),”Energy-Efficiency Policy Opportunities for Electric Motor Driven Systems”, IEA Energy Papers, No. 2011/07, OECD Publishing, Paris.xiv Summary called permanent magnet-assisted synchronous reluctance motors (PMaSynRMs). In this thesis, both SynRMs and PMaSynRMs are investigated. The main focus is given to the rotor design, magnetic material grade and winding configuration. In addition, the modelling and control of SynRMs and PMaSynRMs is also investigated. First, parametrized models are made of the machines. The finite element method (FEM) is used to obtain the dq-axis flux-linkages λd(id, iq, θr) and λq(id, iq, θr) of the SynRM in static 2D simulations, as a function of d-axis current id, and q-axis current iq and rotor position θr. As known, the performance (output torque, power factor and efficiency) of SynRMs depends mainly on the ratio between the direct (d) and quadrature (q) axis inductances (Ld/Lq). This ratio is well-known as the saliency ratio of the SynRM. As magnetic saturation causes significant changes in the inductances and by consequence in the saliency ratio during operation, a SynRM model based on constant inductances (Ld and Lq) is not good enough. It can lead to large deviations in the prediction of the torque capability compared with the real motor. How large these deviations are, is clarified in this thesis by comparing several models that do or do not take into account saturation, cross-saturation and rotor position effects. It is found that saturation and cross saturation must be included in the model for an accurate representation of the SynRM performance and control. This means the flux linkages should be function of id and iq. The rotor position needn’t be included. Apart from the currents, the FEM contains many parameters for the flux barrier geometry, which have a strong influence on the torque and torque ripple of the machine. Next to static simulations, also dynamic simulations are done. In these simulations, the flux-linkages are stored in lookup tables, created a priori by FEM, to speed up the simulations. Based on the SynRM FEM model, the design of the SynRM rotor is investigated. Choosing the flux-barrier geometry parameters is very complex because there are many parameters that play a role. Therefore, an optimization technique is always necessary to select the flux-barrier parameters that optimize the SynRM performance indicators (maximize the saliency ratio and output torque and minimize the torque ripple). To gain insight in the relevant parameters, first a sensitivity analysis is done: the influence of the flux-barrier parameters is studied on the SynRM performance indicators. These indicators are again saliency ratio, output torque and torque ripple. In addition, easy-to-usexv parametrized equations are proposed to select the value of the two most crucial parameters of the rotor i.e. the flux-barrier angle and width. The proposed equations are compared with three existing literature equations. At the end, an optimal rotor design is obtained based on an optimized technique coupled with FEM. The optimal rotor is checked mechanically for the robustness against mechanical stresses and deformations. Apart from the geometry, the electric steel grade plays a major role in the losses and efficiency of an electric machine. Therefore, several steel grades are compared with respect to the SynRM performance i.e. output torque, power factor, torque ripple, iron losses and efficiency. Four different steel grades NO20, M330P-50A, M400-50A and M600-100A are considered. The steel grades differ in thickness and in the losses they produce. It was found that the “best” grade NO20 had in the rated operating point of the considered SynRM 9.0% point more efficiency than the “worst” grade M600-100A. Next to energy-efficiency, a large interest in recent research is dedicated to obtain a high torque density. One of the main techniques to improve the machine torque density is to increase the fundamental winding factor through an innovative winding layout. Among several configurations, the so-called combined star-delta winding layout was proposed in literature several years ago. In the PhD, the combined stardelta winding is compared with the conventional star winding in terms of output torque, torque ripple and efficiency. A simple method to calculate the equivalent winding factor of the different winding connections is proposed. In addition, the modelling of a SynRM with combined star-delta winding is given. Furthermore, the effect of different winding layouts on the performance of the SynRM is presented. To compare both windings experimentally, two stators are made, one with combined star-delta windings and one with conventional star windings, having the same copper volume. Measurements revealed a 5.2% higher output torque of the first machine at rated current and speed. In order to even further improve the power factor and the output torque of the SynRM, ferrite PMs are inserted in the center of the rotor flux-barriers. The rotor geometry of the resulting PMaSynRM is the same as the conventional SynRM. Hence, two rotors with identical iron lamination stack were built: one with PMs and a second one without magnets. Having the two stators and two rotors, a comparison of fourxvi Summary prototype SynRMs is done in the PhD, each of 5.5 kW. Several validation measurements have been obtained. The combined-star delta SynRM with PMs in the rotor had up to 1.5 % point more efficiency than the SynRM with star winding and rotor without magnets at the rated current and speed. As an application of SynRM, an efficient and low cost photovoltaic (PV) pumping system employing a SynRM is studied. The proposed system does not have a DC-DC converter that is often used to maximize the PV output power, nor has it storage (battery). Instead, the system is controlled in such a way that both the PV output power is maximized and the SynRM works at the maximum torque per Ampère, using a conventional three phase pulse width modulated inverter. The design and the modelling of all the system components are given. The performance of the proposed PV pumping system is presented, showing the effectiveness of the system

Computational Intelligence Application in Electrical Engineering

The Special Issue "Computational Intelligence Application in Electrical Engineering" deals with the application of computational intelligence techniques in various areas of electrical engineering. The topics of computational intelligence applications in smart power grid optimization, power distribution system protection, and electrical machine design and control optimization are presented in the Special Issue. The co-simulation approach to metaheuristic optimization methods and simulation tools for a power system analysis are also presented. The main computational intelligence techniques, evolutionary optimization, fuzzy inference system, and an artificial neural network are used in the research presented in the Special Issue. The articles published in this issue present the recent trends in computational intelligence applications in the areas of electrical engineering