Minimizing the number of active switching devices in switched-mode power-electronic systems has a significant importance. Reduced complexity and switching losses, low cost, weight, and volume and ...high reliability are the main merits gained from implementing such reduced switch-count systems. To this end, this paper proposes a new three-phase dc-ac power converter topology for diversified applications based on Zeta dc-dc converter. The proposed power converter employs only four switches and naturally features a reduced-ripple sinusoidal output waveform with a peak line-voltage that could be extended to the full value of the dc-link input voltage. The integral sliding-mode control is employed to optimize the converter dynamics and ensure system robustness during different operating conditions. The proposed inverter topology is analyzed and its performance is validated using both simulations and experimentations.
Recently, magnetic gearboxes (MGBs) are attracting more followers as they offer great benefits over conventional mechanical gearboxes including contactless operation, lower noise, lower vibration, ...and they are maintenance-free. Improving MGBs performance is one of the popular topics under research. Axial MGB is one of the magnetic gear topologies that is suitable for applications which require a physical isolation between the input and output shafts. Unlike radial MGB, axial MGB is relatively simple, has an excellent reliability, and has a relatively low axial force magnitude exerted on the high and low speed rotors. In this paper, an axial MGB with an additional electric power output port is proposed. A conventional 14/4 axial MGB is equipped with Q-phase coils fitted around the ferromagnetic pole-pieces which represent a third output electric port used to sink extra power transmitted from one rotor side to the other side. This extracted output electric power can be used to feed an electrical load while transmitting a mechanical power without using an extra electrical generator. The proposed system is investigated using 3D finite element method analysis.
The interest in multiphase drives has been steadily growing during the last decade due to the promising potentials offered by multiphase machines over conventional three-phase counterpart. In this ...context, six-phase induction machines are preferably used in many diversified high-power applications. Generally, thanks to its improved flux distribution, the asymmetrical six-phase winding topology fed from two three-phase voltage source inverters (VSIs) is commonly employed with isolated neutral points to prevent the flow of zero sequence currents and to limit the number of current controllers to four instead of five when neutral points are connected. In this paper, an innovative design of a six-phase dc-ac inverter is proposed for such type of six-phase ac machines based on the single-ended primary-inductance converter (SEPIC) topology. The proposed topology employs only four active-legs with eight switches with the same output voltage magnitudes as in conventional VSIs and without the mandatory dead-time between switches in the same-leg. Also, it naturally delivers a pure sinusoidal waveform at the output stage. The principle of operation of the proposed inverter topology is investigated in details and assessed through a detailed simulation study of an open-loop control system.
One of the main challenges of voltage source converter based high voltage direct current (VSC-HVDC) transmission systems is the AC faults at the grid side. This work introduces the integration of ...multiphase induction machine (IM) based flywheel energy storage systems (FESS) with VSC-HVDC systems for AC side fault ride through purposes employing modular multilevel converters (MMC). MMCs have become suitable candidates for medium/high power energy conversion systems due to the capability of simply extending the levels of the converter while retaining high levels of reliability. In order to enhance the storage system reliability, a dual three phase IM is used to drive the FESS due to its fault tolerance capability. In this paper, the performance of the FESS is investigated under the operation of a dual three phase IM being driven by two three-phase MMCs. To step-down the DC-link voltage of the HVDC system to a proper voltage level for IMs, the DC-link voltage is divided into two series connected capacitor, and each capacitor voltage is fed as an input DC voltage for each three- phase MMC. The control strategies of the MMCs and the IM are presented, in addition to the IM mathematical model. Simulation case studies are performed using MATLAB/Simulink to validate the proposed system.
Multiphase machines have become serious contenders for safety-critical applications that require wide fault tolerant capabilities and higher system reliability. However, this adds more complexity to ...the adopted power converters. Alternatively, passive transformation is a viable solution to obtain an n-phase supply from the three-phase grid. This paper investigates the existing connections of passive transformation and proposes a transformation, based on the well-known Scott connection, to convert the three-phase grid voltages to an n-phase supply. In comparison with other connections in the literature, the proposed connection uses only two magnetic cores with less number of total coils, hence less total transformer volume. The paper also introduces the general per-phase equivalent circuit for three-phase to n-phase transformer, and the required modifications to conventional open-loop and short-circuit tests to estimate the transformer parameters. A prototype transformer is designed and built to investigate the proposed connection.
This paper illustrates the assessment between the multiloop control strategies that aim to damp the resonance hazard of LCL-filters and expanding the available stability margins. The establishment of ...the multiloop control is sustained in a sensorless manner with the reconstruction of the state variables using the Kalman observer, thus enhancing the cost measures and reliability of the distributed generation (DG) interface. Compared to the conventional multiloop techniques, which is mainly based on the feedback of either the filter capacitor current or voltage, the proposed multiloop method is able to exhibit: 1) theoretical stability through the whole frequency spectrum; 2) higher disturbance rejection originating from the grid-side interference; 3) higher damping of the dominant poles with much lower control effort than the conventional methods; 4) straightforward tuning of the grid current controller as the LCL-filter appears as an apparent standard second order model; and 5) low sensitivity against parameter deviations compared to previous literatures. Furthermore, the utilized control scheme ensures a high quality of injected grid currents under unbalanced and distorted grid voltage conditions. Experimental results validated the proposed control concept through a 3.5 kW setup.
Four-switch three-phase SEPIC-based inverter Diab, M. S.; Elserougi, A.; Abdel-khalik, A. S. ...
IECON 2014 - 40th Annual Conference of the IEEE Industrial Electronics Society,
2014-Oct.
Conference Proceeding
Four-switch three-phase (FSTP) inverter has been proposed as an innovative inverter design to reduce the cost, complexity, size, and switching losses of the DC-AC conversion system. Traditional FSTP ...inverter usually operates at half the DC input voltage, hence, the output line voltage cannot exceed this value. This paper proposes a novel design for the FSTP inverter based on the topology of the single-ended primary-inductance converter (SEPIC). With this topology, the obtained output voltage is a pure sine-wave without a need of an output filter. Compared to the traditional FSTP inverter, the proposed FSTP SEPIC inverter improves the voltage utilization factor of the input DC supply, where the obtained output line voltage can be extended up to the full value of the DC input voltage. For the purpose of optimizing the dynamics of the proposed SEPIC inverter while ensuring correct operation in any working condition, a sliding-mode controller is applied. Derivation of the equations describing the operation of the SEPIC converter based on state space analysis, validation through simulations in MATLAB/SIMULINK and experimental results on a laboratory setup are presented in this paper.
In renewable energy-fed grid-connected applications, voltage source converters (VSC) offer high flexibility and system controllability features. In addition to the stepped down nature of its output ...voltage, the VSC is inherently defenseless against faults. On the other hand, boost Inverters provides voltage boosting characteristic and complete blocking capability between the AC grid and the DC side fault which protects the semiconductor devices during DC faults. A simulation study to compare the performance of VSC and boost inverters during DC side faults is conducted in this paper. The simulation results elucidate a significant decrease in the DC fault current in case of boost inverter due to its blocking capability.
Multiphase Machines offer a promising solution to many practical challenges due to their advantages over the three phase counterparts, as fault-tolerant capability and lower torque ripple magnitude. ...Among different multiphase machines, five-phase machines correspond to a relatively practical selection in industrial applications. Multiphase machines are conventionally fed from voltage source inverter (VSI) as it facilities the operation under open-phase condition but with a sophisticated controller. Among different power converter topologies, current source inverter (CSI) features a simple inverter structure, a lower switching dv/dt, and a reliable short circuit protection. However, the control of multiphase CSI under open phase has not been yet considered in the literature. Additionally, the space vector PWM (SVPWM) of multiphase CSI is still challenging. Alternatively, the mapped sinusoidal PWM can offer simpler control over SVPWM. In this paper, a fault-tolerant controller for a five-phase CSI inverter is introduced and proposed for medium voltage drive applications. The proposed gating signal generator provides a controllable linear modulation index with the availability of over modulation. To verify the proposed fault-tolerant gating signal generator, a five-phase CSI feeds a static R-L load is simulated using MATLAB/SIMULINK as a case study exploring the healthy and the opened-phase cases.
I would like to thank Nwaeze and Mereba for spending a great deal of effort to mitigate some of the concerns raised about the earlier version of this paper. Unfortunately, I have to fall back to my ...role of a critic and express my continuing concerns about the believability of the results and conclusions. To show the reasons for this doubt, I will look at the analysis and retreat to the setting and the underlying institutional aspects of the paper.
