Mitigation of voltage imbalance in power distribution system using MPC-controlled packed-U-cells converter

Delivering high power quality in single-phase distribution has witnessed more challenges especially with the increased penetration of single-phase distributed generation (DG). This paper proposes a smart solid-state-based transformer, which aims to replace traditional ones, for single-phase distribution laterals, and provide load balancing and protection to the three-phase main feeders, that is based on connecting the single-phase lateral to the three-phase main feeder through a power electronics converter. This converter transfers balanced power from and to the three-phase feeder while automatically regulating the lateral single-phase voltage, hence, assuring high power quality without requiring any transformer on-load tap changer. A 7-level packed-U-cells (PUC) single-phase inverter topology was used to deliver single-phase regulated sinusoidal voltage to the AC loads, and at the same time, it is able to deliver DC power to DC loads. The simulation and hardware-in-the-loop (HIL) results have shown that the proposed topology delivers high power quality for both AC and DC loads under different operating scenarios. Moreover, the converter can play the role of a solid-state protection device coordinated with other up- and downstream protective devices. Finally, this system can be integrated within the smart grid allowing more flexibility for automation and efficient control of the grid. - 2019 The Authors. Energy Science & Engineering published by the Society of Chemical Industry and John Wiley & Sons Ltd.This work was made possible by Qatar University Internal Grant no. QUCP?CENG?EE?15/16?4

New fast arctangent approximation algorithm for generic real-time embedded applications

Fast and accurate arctangent approximations are used in several contemporary applications, including embedded systems, signal processing, radar, and power systems. Three main approximation techniques are well-established in the literature, varying in their accuracy and resource utilization levels. Those are the iterative coordinate rotational digital computer (CORDIC), the lookup tables (LUTs)-based, and the rational formulae techniques. This paper presents a novel technique that combines the advantages of both rational formulae and LUT approximation methods. The new algorithm exploits the pseudo-linear region around the tangent function zero point to estimate a reduced input arctangent through a modified rational approximation before referring this estimate to its original value using miniature LUTs. A new 2nd order rational approximation formula is introduced for the first time in this work and benchmarked against existing alternatives as it improves the new algorithm performance. The eZDSP-F28335 platform has been used for practical implementation and results validation of the proposed technique. The contributions of this work are summarized as follows: (1) introducing a new approximation algorithm with high precision and application-based flexibility; (2) introducing a new rational approximation formula that outperforms literature alternatives with the algorithm at higher accuracy requirement; and (3) presenting a practical evaluation index for rational approximations in the literature. - 2019 by the authors. Licensee MDPI, Basel, Switzerland.Funding: The publication of this article was funded by the Qatar National Library.Scopu

MATLAB and PSPICE Dynamic Model of Axial-Field Permanent-Magnet Motor

In this paper a dynamic model of the axial-field, permanent-magnet machine will be discussed. The model may be used to study the transient response with the machine operating as a motor or as a generator. Experimental results are compared with Matlab/Simulink and Pspice predictions for a number of conditions, including the complete starting transient. Excellent correlation is obtained which validated both modeling approaches

A Simulink model of an active island detection technique for inverter-based distributed generation

With the increased involvement of Distributed Power Generation Systems (DPGSs) into the conventional power system, the structure has evolved and therefore has brought in various challenges albeit improving flexibility and smartness of the system. This paper addresses modeling one of these challenges where a Simulink model for inverter-based distributed generation (IBDG) active islanding detection technique is introduced. Out of the various types of active islanding detection methods, the modeling of the general electric islanding detection method which uses the positive feedback of the voltage or frequency at the point of common coupling (PCC) for the detection of an island is presented. This methodology is modeled and applied for an IBDG connected to a low voltage distribution network. The simulation results are presented for a 20kW, three-phase IBDG showing that the system is able to detect islanding and cease the current flow from the IBDG even under critical operating condition of a close matching between the power delivered by the inverter and the load demand (zero nondetection zone operation).Scopu

Analytical Modelling and Simulation of Photovoltaic Panels and Arrays

In this paper, an analytical model for PV panels and arrays based on extracted physical parameters of solar cells is developed. The proposed model has the advantage of simplifying mathematical modelling for different configurations of cells and panels without losing efficiency of PV system operation. The effects of external parameters, mainly temperature and solar irradiance have been considered in the modelling. Due to their critical effects on the operation of the panel, effects of series and shunt resistances were also studied. The developed analytical model has been easily implemented, simulated and validated using both Spice and Matlab packages for different series and parallel configurations of cells and panels. The results obtained with these two programs are in total agreement, which make the proposed model very useful for researchers and designers for quick and accurate sizing of PV panels and arrays

An extraction method for the parameters of the solar cell single-diode-model

This paper introduces an efficient and simple method for extracting the parameters of a solar cell described by a single diode model. Given the IV curve of the solar cell, the method starts with random parameters and relies on an iterative process that moves five key points from the simulated I-V curve closer and closer to the real curve. The implementation of this method gives excellent results in just a few iterations. It also confirms a previously reported fact that quasi-similar I-V curves can be obtained by different sets of parameters. 2018 IEEE.ACKNOWLEDGMENT This publication was made possible by the National Priority Research Program (NPRP) award [NPRP10-1203-160008] from the Qatar National Research Fund (QNRF); a member of the Qatar Foundation. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of QNRF.Scopus2-s2.0-8507634552

Modeling and control for new LLCL filter based grid-tied PV inverters with active power decoupling and active resonance damping capabilities

LLCL filters utilization decreases single-phase transformerless inverter's AC-Side volume significantly. Conversely, the inherent 2nd order power harmonic ripples burden inverters' DC-Side. In fact, the passive solution to buffer these ripples imposes a threat to inverter's reliability and power density. Hence, varieties of active power decoupling methods were introduced in the literature to improve inverter's DC-Side volume and system's reliability. Yet, most existing techniques require auxiliary power electronics and energy storage elements. This contradicts the goal of optimizing system's overall power density. Therefore, a novel LLCL filter for grid-connected applications is introduced that merges AC-Side and DC-Side volume minimization methods without additional power electronics devices. Precisely, the common-mode (CM) operation is harnessed for active power decoupling and the differential-mode (DM) is utilized for active power injection. Besides, the stability analysis of the proposed system revealed that the CM and DM are resonating. Thus, an active resonance damping control scheme based on decoupled CM and DM capacitor currents feedbacks was developed. With the proposed topology, the DC-link capacitor was reduced 40 times compared to the passive solution. The robustness of the proposed solution to the grid-side inductance variation was also verified and validated on 750 W prototype system. 2017 Elsevier B.V.This publication was made possible by the National Priorities Research Program (NPRP) award [NPRP 8-627-2-260] from the Qatar National Research Fund (QNRF) ; a member of the Qatar Foundation. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of QNRF. Appendix A The DM and the CM PR controller�s transfer functions are expressed in Eqs. (44) and (45) , respectively. Note that, these are non-ideal PR controllers with non-ideality damping factor ( ? ). (44) P R d m ( s ) = K P d m + K R d m ( f o ) s s 2 + 2 ? ( 2 ? f o ) s + ( 2 ? f o ) 2 (45) P R c m ( s ) = K P c m + K R c m ( 2 f o ) s s 2 + 2 ? ( 2 ? ( 2 f o ) ) s + ( 2 ? ( 2 f o ) ) 2 + K R c m ( 4 f o ) s s 2 + 2 ? ( 2 ? ( 4 f o ) ) s + ( 2 ? ( 4 f o ) ) 2 In addition, the PI controller used is (46) P I ( s ) = K P ? + K I ? s The transfer function of the HPF used to extract the ripples of the DC supply current is in Eq. (47) . (47) H P F ( s ) = s s + 2 ? f H P F where ( f HPF ) is the HPF cut-off frequency. Finally, the transfer function of the low pass filter (LPF) that is used to filter the DC voltage for the outer voltage regulation loop feedback (48) (48) L P F ( s ) = 2 ? f L P F s + 2 ? f L P F where ( f LPF ) is the LPF cut-off frequency.Scopu