Mohamed S. Diab

A Four-Switch Three-Phase SEPIC-Based Inverter

The 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). The proposed topology provides pure sinusoidal output voltages with no need for output filter. Compared to traditional FSTP inverter, the proposed FSTP SEPIC inverter improves the voltage utilization factor of the input dc supply, where the proposed topology provides higher output line voltage which can be extended up to the full value of the dc input voltage. The integral sliding-mode control is used with the proposed topology to optimize its dynamics and to ensure robustness of the system during different operating conditions. Derivation of the equations describing the parameters design, components ratings, and the operation of the proposed SEPIC inverter is presented in this paper. Simulation model and experimental setup are used to validate the proposed concept. Simulations and experimental results show the effectiveness of the proposed inverter.

A Switched PV Approach for Extracted Maximum Power Enhancement of PV Arrays During Partial Shading

This paper proposes a switched photovoltaic (PV) approach to enhance the extracted maximum power from a PV array during partial shading conditions. The proposed system is simple and cost effective. However, it may provide lower power enhancement compared to other existing solutions, which makes it more suitable for domestic applications. For assessing the proposed switched PV-based system, a detailed numerical comparison between the extracted power from the proposed system and other existing technologies has been presented for the same operating conditions. Simulation and experimental results show the possibility of enhancing the PV arrays extracted output power during partial shading with the proposed system.

A Nine-Switch-Converter-Based Integrated Motor Drive and Battery Charger System for EVs Using Symmetrical Six-Phase Machines

This paper presents a new configuration for integrated on-board battery chargers of electric vehicles (EVs) incorporating symmetrical six-phase machines. The configuration proposes an exclusive utilization of a nine-switch converter (NSC) along with the machine windings during both propulsion and charging of EVs. The proposed configuration has the advantage of employing a reduced number of components in both the EV (on-board) and charging station (off-board), with the privilege of avoiding machine electromagnetic torque production during charging/vehicle-to-grid (V2G) mode of operation. During charging/V2G mode, the NSC is turned into a conventional three-phase pulse width modulation rectifier and is directly connected to the three-phase mains through the machine windings. Conventional three-phase transformers can be employed for galvanic isolation. Switching between propulsion and charging modes is carried out using a simple hardware reconfiguration. Control schemes for both propulsion and charging/V2G modes are elaborated, along with the principles of operation of the NSC. Experimental results are provided to validate the theoretical deductions for the different operating modes.

A Pulsewidth Modulation Technique for High-Voltage Gain Operation of Three-Phase Z-Source Inverters

Z-source inverter (ZSI) was recently proposed as a single-stage buck-boost dc-ac power conversion topology. It augments voltage boost capability to the typical voltage buck operation of the conventional voltage source inverter with enhanced reliability. However, its boosting capability could be limited; therefore, it may not suit applications requiring a high-voltage boosting gain. To enhance the boosting capability, this paper proposes a new pulsewidth modulation (PWM) technique to control the generation of the shoot-through intervals in three-phase ZSIs. The proposed modulation technique achieves a reliable high-voltage gain operation without adding any extra hardware to the ZSI structure, which preserves its single-stage buck-boost conversion nature. In this paper, the principle of the proposed modulation technique is analyzed in detail, and the comparison of the ZSI performance under the conventional and the proposed PWM techniques is given. The simulation and experimental results are shown to verify the analysis of the proposed concept.

Non-linear sliding-mode control of three-phase buck-boost inverter

The development of static power converters capable of transforming DC energy obtained from alternative sources into AC has become one of the main challenges in renewable energy systems. In this context, the buck-boost inverter is advantageous for being capable of providing an AC output voltage higher or lower than the input DC voltage in a single power conversion stage. In this paper, a controller based on the non-linear sliding mode theory is proposed for a three-phase buck-boost inverter to track a desired AC reference voltage. Unlike conventional linear sliding mode controllers that depend on the errors of the state variables, the control law used here depends only on the input and output voltages of the converter without the need to the inductor current measurement, which reduces the system complexity and cost. The proposed controller can not only track the desired reference quickly and accurately, but also achieve a high immunity to external perturbations, such as input voltage and output load disturbances. Several simulation studies are presented in order to investigate the performance of the proposed controller.

A reduced switch-count single-phase SEPIC-based inverter

Recently, reduced switch-count converters have garnered exceptional attention in power electronic systems due to the diversified advantages such as low cost, low weight and volume, and high reliability offered by them. In this paper, a novel design of single-phase inverters with a reduced number of switching devices is proposed based on the single-ended primary-inductance converter (SEPIC). The proposed inverter topology achieves DC to AC conversion using only two switches, and generates a pure sinusoidal AC output voltage without a need for an additional output filter. The reduction in the number of the switching devices contributes to the reduction of the complexity and size of the DC-AC conversion system. The proposed inverter utilizes the DC-link voltage entirely, where the output voltage could be extended up to the full value of the DC input voltage. The integral sliding-mode control is used with the proposed topology to optimize its dynamics, and to ensure robustness of the system during different operating conditions. Operation, analysis, simulations, and experimental results for the proposed inverter topology are included in this paper.

Enhancement of the extracted maximum power of PV array during partial shading using switched PV-based system

This paper proposes a switched PV approach to enhance the extracted maximum power from PV array during partial shading condition. The proposed system is simple and cost effective. However, it may provide lower power enhancement compared to other existing solutions which makes it more suitable for domestic applications. For assessing the proposed switched PV-based system, a detailed numerical comparison between the extracted power from the proposed system and other existing technologies has been presented for the same operating condition. Simulation and experimental results show a possibility of enhancing the PV array extracted output power during partial shading with the proposed system.

Modified modulation scheme for photovoltaic fed grid-connected three-phase boost inverter

Transformer-less photovoltaic (PV) inverters are the major functional units of modern grid-connected PV energy production systems. In general, two power conversion stages are required when low-voltage unregulated photovoltaic (PV) output is conditioned to generate AC power. In this paper, the boost inverter topology that achieves both boosting and inversion functions in a single stage is used as a building block to develop a three phase grid connected PV system which offers high conversion efficiency, low-cost and compactness. The proposed system employs a modified modulation scheme for the three phase boost inverter to control both active and reactive power injected to the grid. This modified modulation scheme enhances the boosting capability of the boost inverter and improves the THD of the grid injected current. Moreover, it reduces the voltage stress on the capacitors and switching devices. Analysis and simulation results are presented to confirm the advantages and efficiency of the proposed modulation technique.

A Zeta-converter based four-switch three-phase DC-AC inverter

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.

A reduced switch-count SEPIC-based inverter for asymmetrical dual three-phase induction machines

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.