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The main advantage of DC-linked type quasi-switched boost inverter is the low voltage stress on the impedance-source network devices when compared with quasi-Z-source inverter (qZSI). In this paper, a DC-linked quasi-switched boost cascaded multilevel inverter (DqSB-CMI) is proposed. This paper further addresses detailed modeling and control issues of the DqSBI-CMI used for grid-tied applications. The proposed system can solve the imbalance problem of DClink voltage and the power between different modules, providing the desired power to the grid. Simulation and experimental results are presented to verify the control system and theoretical analysis of the DqSB-CMI.

Low voltage stress on the impedance source network devices is the main reason for the advent of DC-linked type quasi-switched boost inverters (DqSBIs). However, the DqSBI has become less attractive due to its low voltage gain. This paper presents a novel PWM control strategy for the DqSBI and its comparative performance evaluation to the conventional inverters. The modified PWM control strategy based DqSBI improves the voltage gain and reduces the conduction loss and the inductor current ripple. Circuit analysis and comparison study between the DqSBI, the quasi-Z-source inverters, and the two-stage inverter with a boost DC-DC converter are presented. 1-kVA three-phase inverter prototypes were set up to compare and evaluate the performance of the DqSBI with the improved PWM method for voltage gains of 0.85 to 1.6. The measured efficiency and total harmonic distortion (THD) values are also presented.

This paper presents some comparative results between the three-phase quasi-Z source inverter (qZSI)and active quasi-Z source inverter (AqZSI). An improved PWM method is proposed for AqZSI. The voltage gain can be increased by using the shoot-through duty cycle and the switching ratio of the additional switch. Compared to qZSI, AqZSI with improved PWM strategy has a higher efficiency at the boost mode. Furthermore, AqZSI can be operated up to a higher modulation index and it boasts a lower inductor current ripple and reduced shoot-through current. The analysis of inverter and the improved PWM strategy are discussed. An experimental prototype with output power of 600 W is built to show the agreement of theory and measurement.

The DC-link type quasi-switched boost inverters (DCL-qSBIs) are known as one of impedance-source inverters with low voltage stress on their additional switch, diode, and capacitor. However, the voltage gain of DCL-qSBIs is still low. This paper presents DCL-qSBIs with a modified PWM control strategy. The modified PWM control strategy based DCL-qSBIs improve voltage gain, reduce the conduction loss, and decrease the voltage stress of devices in the switched-boost network. The operating principle of DCL-qSBIs is presented. The 1 kVA-prototype three-phase DCL-qSBI and quasi-Z-source inverter (qZSI) is built to evaluate the performance of the inverters at output voltage ratio of 1.05 to 1.6. The measured efficiency of DCL-qSBI is 0.5 to 1% higher than that of the qZSI at all powers and boost levels tested.

In this paper, a modified three-phase two-level voltage source inverter is proposed. By combining the conventional three-phase H-bridge inverter with a switched-capacitor-voltage-doubler network, the DC-link voltage of the proposed inverter is double with respect to the input DC voltage. As a result, the output voltage of the proposed inverter can be higher than the input DC voltage. Furthermore, a common-mode voltage (CMV) of the proposed inverter can be reduced through controlling the two additional switches based on the space vector pulse-width modulation. Compared to the existing modulations and topologies, the variation in CMV can only be up to 16.6% of DC-link voltage. Furthermore, the voltage stress across additional switches and diodes is equal to half of DC-link voltage. Mathematical analysis, operating principles, and comparison of the proposed three-phase two-level voltage source inverter with the conventional three-phase voltage source inverters are presented. The simulation results based on PLECS software verify a good performance of the proposed inverter. Finally, a laboratory prototype based on a TMS320F280049 DSP is developed and experimental tests are carried out to validate the effectiveness of the proposed three-phase inverter topology.

In this study, an improved pulse width modulation (PWM) scheme was proposed for an active quasi-Z source inverter (AqZSI). Compared to the quasi-Z-source inverter (qZSI), the AqZSI with improved PWM strategy can operate in a wide range of input voltage with higher efficiency. Furthermore, the AqZSI can operate with a higher modulation index, a lower inductor current stress, and a reduced shoot-through current. A procedure flowchart is presented for the optimal selection of the shoot-through duty cycle, the switching ratio of the additional switch, and the modulation index for AqZSI. Moreover, some comparative results between the AqZSI, qZSI and conventional two-stage inverter with a boost DC–DC converter are shown in detail. Finally, 1.2 kVA SiC-based three-phase inverter prototypes are built to verify the agreement between theory and measurement.