Ahmed Abdelhakim

Three-Phase Split-Source Inverter (SSI): Analysis and Modulation

In several electrical dc-ac power conversions, the ac output voltage is higher than the input voltage. If a voltage-source inverter (VSI) is used, then an additional dc-dc boosting stage is required to overcome the step-down VSI limitations. Recently, several impedance source converters are gaining higher attentions [1], [2], as they are able to provide buck-boost capability in a single conversion stage. This paper proposes the merging of the boost stage and the VSI stage in a single stage dc-ac power conversion, denoted as split-source inverter (SSI). The proposed topology requires the same number of active switches of the VSI, three additional diodes, and the same eight states of a conventional space-vector modulation. It also shows some merits compared to Z-source inverters, especially in terms of reduced switch voltage stress for voltage gains higher than 1.15. This paper presents the analysis of the SSI and compares different modulation schemes. Moreover, it presents a modified modulation scheme to eliminate the low frequency ripple in the input current and the voltage across the inverter bridge. The proposed analysis has been verified by simulation and experimental results on a 2.0-kW prototype.

Analysis and modulation of the buck-boost voltage source inverter (BBVSI) for lower voltage stresses

Renewable energy sources entail the power electronics inverters are the orbit of research objectives for optimum operation. Two commonly used inverters exist; the current source inverters (CSI) and the voltage source inverters (VSI). The first one supports only the boost capability and the other supports the buck capability, but due to the high variation of the output voltage of these renewable energy sources a buck-boost capability is a must. This buck-boost capability requires the enforcement of the aforementioned inverters with an additional stage for the amendment of the energy source output, which greatly reduces the overall efficiency. Instead of such two stage power conversion operation, a single stage operation could be obtained using the Z-source inverter (ZSI). The so-called ZSI exploits an impedance network to achieve such capability. This impedance network comprises four passive elements and a semiconductor switch, which is relatively bulky and costly. This paper proposes the analysis and the modulation scheme of another inverter topology, called the buck-boost voltage source inverter (BBVSI), to get the buck-boost capability in a single stage power conversion operation with less passive elements and less semiconductor devices ratings. The BBVSI topology exploits only two passive elements in addition to a semiconductor switch to give the same function of the ZSI with some merits over it. Moreover, this paper compares the BBVSI topology with the ZSI topology. The performance of the BBVSI topology is evaluated using MATLAB/Simulink models.

Three-Phase Three-Level Flying Capacitors Split-Source Inverters: Analysis and Modulation

Single-stage dc–ac power converters with boost capabilities offer an interesting alternative compared to two-stage architecture. One of the recently proposed single-stage dc–ac power converters is the split-source inverter (SSI). This paper extends the SSI topology from the two-level operation to the three-level one using the flying capacitors (FCs) configuration. Among the diode-clamped SSI (DC-SSI) and FC-SSI, the second one is proposed in order to avoid the need of two isolated dc sources. This paper shows that the FC-SSI provides additional merits compared to the two-level SSI in terms of input inductance requirements using the same switching frequency, voltage stresses across the active switches, and total harmonic distortion of the output voltage. Such results are obtained by discussing the analysis and the modulation of this topology, considering some simulation results, and comparing it to some other existing topologies to show its properties and limitations. Finally, a reduced-scale 1.5-kVA three-level FC-SSI is implemented experimentally to validate its functionality and verify the proposed analysis and modulation properties.

Three-level operation of the split-source inverter using the flying capacitors topology

Split-source inverter (SSI) topology is one of the recently proposed single-stage dc-ac power converters, which has some merits compared to other equivalent topologies. The SSI was proposed as a two-level topology. Hence, this paper extends its operation from two level operation to a three-level equivalent using the standard three-level flying capacitors voltage-source inverter (VSI) bridge. The extra merit behind this extension is the lower inductance requirements using the same switching frequency, in addition to the conventional merits of the three-level operation. The introduced three-level flying capacitors SSI (FC-SSI) is analyzed and simulated in this paper using MATLAB/Simulink model, where a 1.5kV A system is designed, simulated, and finally implemented experimentally to verify the simulation results.

Analysis of the three-level diode-clamped split-source inverter

This paper studies the integration of the two-level split-source inverter (SSI) concept into the three-level diode-clamped inverter configuration. The proposed three-level diode-clamped-based SSI (3L-DC-SSI) uses two isolated dc sources, two inductors, two capacitors, and six input diodes with the three-level diode-clamped bridge. This topology introduces lower current stresses of the switches compared to the three-level flying capacitors-based SSI (3L-FC-SSI). Moreover, the 3L-DC-SSI has the ability to be operated from two unequal isolated dc sources, where its modulation and mathematical derivation in this case is discussed as well. On the other hand, this topology has some limitations in terms of the higher voltage stresses and the low frequency component in the input current and the inverter voltage. The 3L-DC-SSI is analyzed in this paper using the standard space vector modulation scheme, where simulation results of a 30 kVA system are introduced.

Switching Loss Reduction in the Three-Phase Quasi-Z-Source Inverters Utilizing Modified Space Vector Modulation Strategies

Several single-stage topologies have been introduced since kicking off the three-phase Z-source inverter (ZSI), and among these topologies, the quasi-ZSI (qZSI) is the most common one due to its simple structure and continuous input current. Furthermore, different modulation strategies, utilizing multiple reference signals, have been developed as well. However, prior art modulation methods have some demerits, such as the complexity of generating the gate signals, the increased number of switch commutations with continuous commutation at high current level during the entire fundamental cycle, and the multiple commutations at a time. Hence, this paper proposes two modified space vector modulation strategies, aimed at the reduction of the qZSI number of switch commutations at high current level for shorter periods during the fundamental cycle, i.e., reducing the switching loss, simplifying the generation of the gate signals by utilizing only three reference signals, and achieving a single-switch commutation at a time. These modulation strategies are analyzed and compared to the conventional ones, where a reduced-scale 1-kVA three-phase qZSI is designed and simulated using these different modulation strategies. Finally, the 1-kVA three-phase qZSI is implemented experimentally to validate the performance of the proposed modulation strategies and verify the reported analysis.

Split-source inverter

Single-stage DC-AC power converters are recently gaining higher popularity due to their features in terms of size, cost, weight, and complexity of the whole system. Different topologies exist, where the Z-source inverter, the buck-boost voltage source inverter, and the Y-source inverter are the common topologies. This paper proposes another single-stage DC-AC power converter, called the split-source inverter. The proposed topology has some merits over the other topologies, the main being the possibility to use the same modulation schemes of the conventional voltage source inverter without any modification. The operation of the split-source inverter is studied and analyzed in this paper then verified using MATLAB/Simulink models. Finally a small-scale prototype is used to confirm the functionality of the proposed idea.

Performance Evaluation of the Single-Phase Split-Source Inverter Using an Alternative DC–AC Configuration

This paper investigates and evaluates the performance of a single-phase split-source inverter (SSI), where an alternative unidirectional dc–ac configuration is used. Such configuration is utilized in order to use two common-cathode diodes in a single device instead of using two separate diodes, resulting in minimum parasitic inductance in the commutation paths. In this paper, the analysis and modulation of the single-phase SSI using this alternative configuration is discussed, and the analysis of the low-frequency component in the dc side is introduced. Moreover, the features behind employing the triangular, the trailing-edge sawtooth, and the leading-edge sawtooth carriers with the single-phase SSI are discussed, and the differences among these carriers are highlighted. In order to highlight the performance of the proposed SSI, a comparative study is conducted with the two-stage architecture and the single-phase quasi-Z-source inverter (qZSI). The introduced analysis is enhanced with simulation results using MATLAB/PLECS models, where a 1-kVA single-phase SSI is designed and simulated. Finally, the designed 1-kVA single-phase SSI is implemented experimentally and tested at different operating points, i.e., at different voltage gains, and a maximum efficiency of

Decoupled control scheme of the grid-connected split-source inverter for renewable energy sources

95.5\%

Analysis and Design of the Quasi-Z-Source Inverter for Wide Range of Operation

is obtained.