In this paper, a three-level quasi-switched boost T-type inverter (3L qSBT ² I) is proposed. A new pulse-width modulated (PWM) control method is presented to reduce the inductor current ripple of the qSBT ² I. In the introduced PWM technique, the shoot-through duty cycle is maintained constant to keep the modulation index as high as possible. Then, the only control parameters of the qSBT ² I are the duty cycles of the two additional switches. By controlling the duty cycles of the two additional switches, the voltage gain of the proposed qSBT ² I can be improved to a value larger than that of the conventional 3L impedance source inverters. The steady-state analysis, operating principles, and comparisons with the impedance source-based 3L inverters are presented. A 1-kW prototype is constructed to verify the operating principle of the 3L qSBT ² I. An indirect dc-link voltage regulator and a capacitor voltage-balance controller are applied to the proposed qSBT ² I. Simulation and experimental results are presented.

In this paper, a new optimal pulse-width modulation (PWM) scheme for a three-level quasi-switched boost T-type inverter (TL qSBT2I) under normal and failure modes is proposed. The proposed method reveals its semiconductor fault tolerance capability in open-circuit fault condition situations as described in the paper. The PWM control algorithm for the fault-tolerant qSBT2I is implemented by selecting appropriate values for the modulation index, shoot-through (ST) duty cycle and duty cycles of two additional switches. The steady-state analysis and operating principles of the fault-tolerant qSBT2I are presented. A laboratory prototype was built to verify the operating principles of the qSBT2I with the proposed modulation scheme before and after fault conditions.

In this paper, the effect of common-mode voltage generated in the three-level quasi-switched boost T-type inverter is minimized by applying the proposed space-vector modulation technique, which uses only medium vectors and zero vector to synthesize the reference vector. The switching sequence is selected smoothly for inserting the shoot-through state for the inverter branch. The shoot-through vector is added within the zero vector in order to not affect the active vectors as well as the output voltage. In addition, the shoot-through control signal of active switches of the impedance network is generated to ensure that its phase is shifted 90 degrees compared to shoot through the signal of the inverter leg, which provides an improvement in reducing the inductor current ripple and enhancing the voltage gain. The effectiveness of the proposed method is verified through simulation and experimental results. In addition, the superiority of the proposed scheme is demonstrated by comparing it to the conventional pulse-width modulation technique.

This article presents control techniques for three-level boost T-type inverter (TLB-T ² I) to address open-circuit faults (OCFs) and short-circuit faults (SCFs) of semiconductor devices. Three main groups of semiconductor failures of TLB-T ² I are OCFs of boost switches ( F 1), OCFs of inverter half bridge switches ( F 2), and OCFs of bidirectional switches ( F 3). Under the proposed approaches, the inverter generates a two-level output voltage with the F 1 and F 2 faults, while it still generates a three-level output voltage with the F 3 fault. These control techniques are extended to solve OCF and SCF of diodes, SCF of boost switches, and OCF of capacitors. Operating modes of the inverter in both normal and fault conditions are presented. Design guidelines, power loss contribution, and comparison study are included. The experimental results based on a 1-kVA prototype are carried out to verify the accuracy of the proposed methods. The result shows that the proposed methods can reduce component voltage ratings when compared to the conventional methods. In particular, the voltage rating of the inverter half-bridge switch in the F 2 fault-tolerant method is reduced by at least 50% compared to the traditional techniques.

This paper introduces a space vector control method for the three-level quasi-switched boost T-type inverter (3L-qSBT2I) which provides some benefits such as good output voltage quality, high voltage gain, and low voltage stress on power devices. By applying corresponding P-type or N-type small vectors in the switching sequence, the neutral-point voltage unbalance problem can be solved easily. The advantage of this modulation solution is that it does not require any extra calculations. The upper-shoot-through (UST) and lower-shoot-through (LST) states are utilized instead of full-shoot-through (FST), which is usually used in traditional single-stage three-level impedance source inverter, to ensure the boost capability of the inverter. These states are inserted into small vectors in order not to affect the output line-to-line voltage. Some investigations about voltage gain, diode, and switch voltage stress have been conducted to demonstrate the effectiveness of the proposed method. The experimental results are also presented to validate the accuracy of the proposed modulation method. The proposed approach has resulted in an efficiency rise by 2% as compared to the conventional PWM scheme.

A new modulation strategy has been introduced in this paper in order to enhance the boost factor for the three-level quasi-switched boost T-type inverter (3L-qSBT²I). Under this approach, the component rating of power devices is significantly decreased. Moreover, the use of a larger boost factor produces a smaller shoot-through current. This benefit leads to reducing the conduction loss significantly. Furthermore, the neutral voltage unbalance is also considered. The duty cycle of two active switches of a quasi-switched boost (qSB) network is redetermined based on actual capacitor voltages to recovery balance condition. Noted that the boost factor will not be affected by the proposed capacitor voltage balance strategy. The proposed method is taken into account to be compared with other previous studies. The operation principle and overall control strategy for this configuration are also detailed. The simulation and experiment are implemented with the help of PSIM software and laboratory prototype to demonstrate the accuracy of this strategy.