6 research outputs found
Torque Ripple Minimization for a Permanent Magnet Synchronous Motor Using a Modified Quasi-Z-Source Inverter
This paper presents a torque ripple minimization method for a permanent magnet synchronous motor (PMSM) drive system that utilizes a modified quasi-Z-source (qZS) inverter. The proposed modified qZS network is designed by adding an extra switching device to the conventional qZS topology and provides a wider range of capabilities for inverter input voltage control, e.g., both step-up and step-down operations. It also allows for modification of the traditional switching sequence selection scheme when using the space vector modulation (SVM) for switching. The provided flexibilities are leveraged to develop a control system that minimizes the torque ripples during PMSM operation while satisfying conventional control objectives such as shaft speed control. The control system is comprised of an input voltage optimization subsystem with the goal of torque ripple minimization, which provides the reference for a cascaded modulated model predictive control subsystem for the modified qZS network control, and a motor side predictive control subsystem. The control system employs a new switching sequence selection scheme for SVM modulation to further reduce PMSM torque ripples. Experimental results are provided to validate the theoretical outcomes
Power Converters in Power Electronics
In recent years, power converters have played an important role in power electronics technology for different applications, such as renewable energy systems, electric vehicles, pulsed power generation, and biomedical sciences. Power converters, in the realm of power electronics, are becoming essential for generating electrical power energy in various ways. This Special Issue focuses on the development of novel power converter topologies in power electronics. The topics of interest include, but are not limited to: Z-source converters; multilevel power converter topologies; switched-capacitor-based power converters; power converters for battery management systems; power converters in wireless power transfer techniques; the reliability of power conversion systems; and modulation techniques for advanced power converters
Model Predictive Control Technique of Multilevel Inverter for PV Applications
Renewable energy sources, such as solar, wind, hydro, and biofuels, continue to gain
popularity as alternatives to the conventional generation system. The main unit in the renewable
energy system is the power conditioning system (PCS). It is highly desirable to obtain higher
efficiency, lower component cost, and high reliability for the PCS to decrease the levelized cost of
energy. This suggests a need for new inverter configurations and controls optimization, which can
achieve the aforementioned needs. To achieve these goals, this dissertation presents a modified
multilevel inverter topology for grid-tied photovoltaic (PV) system to achieve a lower cost and
higher efficiency comparing with the existing system. In addition, this dissertation will also focus
on model predictive control (MPC) which controls the modified multilevel topology to regulate
the injected power to the grid. A major requirement for the PCS is harvesting the maximum power
from the PV. By incorporating MPC, the performance of the maximum power point tracking
(MPPT) algorithm to accurately extract the maximum power is improved for multilevel DC-DC
converter. Finally, this control technique is developed for the quasi-z-source inverter (qZSI) to
accurately control the DC link voltage, input current, and produce a high quality grid injected
current waveform compared with the conventional techniques.
This dissertation presents a modified symmetrical and asymmetrical multilevel DC-link
inverter (MLDCLI) topology with less power switches and gate drivers. In addition, the MPC
technique is used to drive the modified and grid connected MLDCLI. The performance of the
proposed topology with finite control set model predictive control (FCS-MPC) is verified by
simulation and experimentally. Moreover, this dissertation introduces predictive control to achieve
maximum power point for grid-tied PV system to quicken the response by predicting the error
before the switching signal is applied to the converter. Using the modified technique ensures the
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system operates at maximum power point which is more economical. Thus, the proposed MPPT
technique can extract more energy compared to the conventional MPPT techniques from the same
amount of installed solar panel.
In further detail, this dissertation proposes the FCS-MPC technique for the qZSI in PV
system. In order to further improve the performance of the system, FCS-MPC with one step
horizon prediction has been implemented and compared with the classical PI controller. The
presented work shows the proposed control techniques outperform the ones of the conventional
linear controllers for the same application. Finally, a new method of the parallel processing is
presented to reduce the time processing for the MPC
Isolated Single-stage Power Electronic Building Blocks Using Medium Voltage Series-stacked Wide-bandgap Switches
The demand for efficient power conversion systems that can process the energy at high power and voltage levels is increasing every day. These systems are to be used in microgrid applications. Wide-bandgap semiconductor devices (i.e. Silicon Carbide (SiC) and Gallium Nitride (GaN) devices) are very promising candidates due to their lower conduction and switching losses compared to the state-of-the-art Silicon (Si) devices. The main challenge for these devices is that their breakdown voltages are relatively lower compared to their Si counterpart. In addition, the high frequency operation of the wide-bandgap devices are impeded in many cases by the magnetic core losses of the magnetic coupling components (i.e. coupled inductors and/or high frequency transformers) utilized in the power converter circuit.
Six new dc-dc converter topologies are propose. The converters have reduced voltage stresses on the switches. Three of them are unidirectional step-up converters with universal input voltage which make them excellent candidates for photovoltaic and fuel cell applications. The other three converters are bidirectional dc-dc converters with wide voltage conversion ratios. These converters are very good candidates for the applications that require bidirectional power flow capability. In addition, the wide voltage conversion ratios of these converters can be utilized for applications such as energy storage systems with wide voltage swings
Deadbeat current control of qZS based grid-connected multilevel inverter
This paper proposes a Current Deadbeat Control (DBC) algorithm for a three-phase 9-cells qZS based Cascaded H-Bridge (CHB) inverter to ensure grid current supply with low THD. The studied topology is considered as a single-stage DC/AC topology having the capability of boosting the DC input voltage with high-quality multilevel AC voltage, independent DC-link voltage compensation, and control of the power transfer with high reliability. Moreover, a Repetitive Controller (RC) is connected to the inductor current loop with the aim to reject periodic disturbances (double line-frequency fluctuations). The employed RC has the capability of learning through iterations based on tracking error. During the control, the compensation method uses the error between the DC-link peak voltage reference and the actual value to produce the compensating inductor current reference. Theoretical analysis and simulation results shows that the proposed solution achieves high dynamic performance and reduced cyclical disturbances effects. 2017 IEEE.ACKNOWLEDGMENT This work was made possible by NPRP-EP Grant no. X-033-2-007 from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors.Scopu