EPE Journal Volume 20-4  
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EPE Journal Volume 20-4 - Editorial
EPE Journal Volume 20-4 - Papers
EPE Journal Volume 20-4 - The News



 EPE Journal Volume 20-4 - Editorial 

Signature of the Joint Sponsors’ Agreement and Operations Agreement between IEEE-PELS and EPE Association  [Details]
By B. Sneyers
The editorial of EPE Journal Volume 20-4: Signature of the Joint Sponsors’ Agreement and Operations Agreement between IEEE-PELS and EPE Association


 EPE Journal Volume 20-4 - Papers 

Analysis of the Boundaries to Compensate Voltage Sag Events Using a Single Phase Multi-Level Rectifier  [Details]
By C. Nunez; J. Lira; N. Visairo; R. Echavarría
In this paper, it is established analytically the operation boundaries of the Single Phase Multi-Level Rectifier with voltage sag ride through capability (SPMLR with extended function). The analysis is based on its mathematical model and the switches power losses equations. These limits have been defined in terms of duty cycle, maximum current and power losses of the switches when voltage sag occurs. This information is very useful for converter design and for control purposes since safe operation and boundaries to compensate voltage sag are analytically known. To validate this analysis, simulation and experimental results are shown in a 1 kVA prototype.

A Low-Cost High Power Factor Battery Charger based on Standard Peak-Current Mode Integrated Controllers  [Details]
By D. G. Lamar; J. Sebastian; M. Arias; A. Rodriguez; M.M. Hernando
In recent years, several low-cost Power Factor Corrector (PFC) control techniques operating in Continuous Conduction Mode (CCM) have been proposed to simplify traditional control strategies based on a multiplier. This simplification makes sense in the case of relatively low-power, low-cost and wide input voltage range applications. These techniques revolve above the Boost converter as a first stage of a.c.-d.c. power supplies, because their application in other topologies is more expensive and complex. In some applications, however, a PFC can be used as a one-stage power supply. This paper presents a new low-cost control strategy suitable for the Flyback family of PFCs (e.g., Buck-Boost, Flyback, SEPIC, Cuk and ZETA). Control is carried out by a standard Peak Current-Mode Integrated Controller (PCMIC) for d.c.-d.c. converters. Neither an analog multiplier nor an input voltage sensor is needed to achieve quasi-sinusoidal line waveforms, which makes this method very attractive for low-cost applications. In fact, this method is the simplification of One Cycle Control (OCC), also called Linear Peak Current Mode Control (LPCMC), applied to the Flyback family of PFCs. In this case, the use of a simple exponential compensation ramp instead of linear ramp is the proposed solution for reducing the Total Harmonic Distortion (THD). Moreover, the line current is cycle-by-cycle controlled and therefore the input current feedback loop is extremely fast, thus allowing the use of this type of control with high frequency lines. Finally, an experimental prototype of a battery charger was developed as a high Power Factor (PF) power supply to verify the viability of the new control strategy.

Robust PLL Algorithm for Three-Phase Grid-Connected Converters  [Details]
By A. Bellini; S. Bifaretti; V. Iacovone
The estimation of the grid angle is a key factor in the control of many power electronics applications using gridconnected three-phase converters. The knowledge of the grid angle is required for different goals such as the synchronization of the voltage or current waveforms produced by the converter to the utility grid, the power flow management and the reduction of the transients generated on grid failures or on the reconnection of the converter.
Generally, the grid voltages are polluted with harmonics and affected by amplitude unbalances; thus, oscillation on the grid angle signal can lead to an improper synchronization between the converter outputs and the grid voltages. To improve the synchronization, the paper proposes a robust PLL structure employing a prediction-correction filter based on a second-order linear and time-invariant observation model. Such filter is able to provide an accurate tracking of the grid voltage angle also in critical operating conditions. The paper describes also the implementation on a low cost fixed-point DSP controller and a comparison, obtained by simulation, with traditional filters. Finally, some significant experimental results validate the performances of the proposed approach.

Stator-Permanent-Magnet Reluctance Generator using Ferrite Magnet for Small-Scale Renewable Energy Generation  [Details]
By Kenji Nakamura, Jun Yoshida, Osamu Ichinokura
This paper discusses a stator-permanent-magnet reluctance generator (PMRG) (Fig. 1). The PMRG has a doubly salient pole structure, and has permanent magnets embedded in the stator yoke. Concentrated windings are arranged individually around each stator pole. On the other hand, the rotor has neither permanent magnets nor windings. Therefore, the PMRG has a simple and robust structure, and permits a multipolar structure. It is expected that the PMRG is applied into a small-scale wind-turbine and hydroelectric power generation. However, two major technical problems still remain. One is the cost of rare-earth magnets, and the other is torque ripple due to the doubly salient pole structure.
First, this paper presents a PMRG using ferrite magnets. The ferrite magnet has about three times lower residual magnetic flux density as compared to the rare-earth magnet, but has about 10 times lower cost. It is demonstrated that the proposed PMRG using ferrite magnets has almost the same output power as that using rare-earth magnets by employing an outer rotor structure (Fig. 4). In addition, its material cost is lower by about 45 %.
Next, it is proposed a method for reducing torque ripple of the PMRG by stacking two rotors (Fig. 10). One rotor is shifted by 180º in electrical angle from the other rotor. In addition, the rotor pole-tips are cut off so that the torque waveform consists of only odd-harmonics. In such a structure, the torque ripple of the PMRG can be completely cancelled in theory.
Finally, a trial two-stacked outer-rotor PMRG has been manufactured. The maximum output power is 777 W at 1000 rpm, and the efficiency at the point is 84.5 %. In addition, the efficiency at less than 1000 rpm is improved by over 10 % in comparison with the present PMRGs with rare-earth magnets (Fig. 19).

Design of a Digital System Dedicated for Electrical Drive Applications  [Details]
By N. AL_Sheakh Ameen, A. A. Naassani, R. M. Kennel
The aim of this paper is to present the design of a rapid prototype drive system with small size, low cost and high effi-ciency. It depends basically on the personal computer (PC) processor without the need for any external processor (e.g. digital signal processor (DSP)) to get fast execution of control algorithms, and to support floating point operations. The PC-based rapid-prototyping system is dedicated for laboratory purposes and consists of an extension kit with all required interface boards to perform the simulation and implementation of electrical drive algorithms. Almost all designed boards are based on programmable-logic devices (PLD) to reduce cost and size. To operate the hardware of the proposed system, a free available open source real-time operating system (RTOS) kernel under Linux is used. A case study from electric drive area is selected and numerous experimental results are given in order to demonstrate the good functionality of the conceived system.

Reliability & Availability of Wind Turbine Electrical & Electronic Components  [Details]
By P. Tavner, S. Faulstich, B. Hahn, G.J.W. van Bussel
Recent analysis of European onshore wind turbine reliability data has shown that whilst wind turbine mechanical subassemblies tend to have relatively low failure rates but long downtimes, electrical and electronic subassemblies have relatively high failure rates and short downtimes. For onshore wind turbines the higher failure rates of electrical and electronic subassemblies can be managed by a maintenance regime that provides regular and frequent attendance to wind turbine sites. This regime will be costly or impossible to sustain in more remote onshore or offshore wind farm sites. This paper gathers data supporting the contention that electrical and electronic subassembly failure modes are a significant contributor to wind turbine unreliability, identifying some of their root causes, showing how they will play a more significant part in the availability of offshore wind turbines. The paper concludes by showing how more can be learnt to eliminate or mitigate some of these electrical and electronic subassembly failure modes.

Evaluation of the Effect of Voltage Sags Due to Grid Balanced and Unbalanced Faults on DFIG Wind Turbines  [Details]
By Xiangwu Yan, Giri Venkataramanan, P. S. Flannery, YangWang, Bo Zhang
This paper demonstrated the dynamic behavior of DFIG wind turbine during grid balanced and unbalanced faults by using simulation results, the effect of voltage sag on DFIG wind turbine is discussed through comparing of the various voltage sag depth in a type of fault lengthways and contrasting various fault type in the same voltage sag depth horizontally. The response characteristics of DFIG wind turbine during PCC voltage sags are summarized by a typical example. Finally it is clear that some countermeasures on the rotor side convertor or the stator side must be taken into account for DFIG wind turbine ride through PCC extreme voltage sag.


 EPE Journal Volume 20-4 - The News 

EPE Journal Volume 20-4 - The News  [Details]
By B. Sneyers
Building Integrated PV Systems International workshop (11/12 April 2011, Delft University of Technology, The Netherlands)
EPE Joint Wind Energy and T&D Chapters Seminar (The Norwegian University of Science and Technology, NTNU, Trondheim, Norway)
ECPE Image film “Power Electronics – The key to Energy Efficiency”