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 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.

The conventional three-level T-type inverter (3L-T2I) can solve open-circuit fault (OCF) at any switching devices by itself. However, the conventional fault-tolerant (FT) methods for upper switch of 3L-T2I have a low voltage gain which cannot ensure the inverter operation in low voltage range. In order to improve the voltage-gain of the inverter under faulty condition, this paper presents a new topology of FT-3L-T2I by adding one normally-closed relay. This extra relay connects the mid-point of DC-link voltage and the common-point of bi-directional switches, in normal operating. In post-fault operating, this relay is opened. A new FT 2-level space-vector modulation (SVM) technique is introduced to control the proposed inverter. Under this SVM method, the operation of faulty upper switch is recovered by bi-directional switches and upper switches of other healthy phases. By this way, the voltage gain of the FT-3L-T2I can increase 2/3 times than conventional methods. Unlike any traditional method, under this approach, the unbalanced neutral-point voltage cannot affect the output voltage. The experimental results based on 900-kVA laboratory prototype are introduced to verify the effectiveness of the proposed inverter and SVM control strategy.

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.

This paper proposes a novel single-stage three-level buck-boost inverter based on voltage multiplier cells. The characteristics of the proposed topology are listed as 1) providing buck-boost operation in a single-stage power conversion, 2) reducing the number of components, 3) low component rating, and 4) automatic capacitor voltage balance without requiring any voltage sensors. A space-vector modulation (SVM) technique is introduced to control the proposed inverter and improve the quality of the output voltage waveform. In the SVM scheme, three nearest vectors are used to generate the output voltage vector in any switching period. The upper-shoot-through switching state is adopted to provide buck-boost operations. This state is added within the small N-type vectors. The operating states, steady-state analysis, component selections, and comparison analysis are detailed. A 1-kVA laboratory prototype is built to validate the effectiveness of the proposed inverter. The experimental results show that the switch operates under a zero-voltage switching conditions for both turning-on and -off. Moreover, the capacitor voltage self-balanced characteristic keeps the voltage difference within 3.8% of the average capacitor voltage.

The combination of conventional front-end DC-DC converter and H-bridge inverter has been proposed with common-ground (CG) characteristic and voltage booting capability. However, it has drawbacks of low modulation index utilization which causes high component voltage rating and small conversion efficiency. In this paper, a new topology of a single-phase common-ground buck-boost inverter (1P-CG-BBI) is presented to overcome existing drawbacks of conventional CG inverters. The proposed 1P-CG-BBI uses one more active-switch and one more diode than traditional CG inverter. Note that the proposed inverter still shares the same ground for DC input source and AC output voltage, which completely eliminates the leakage current. A hybrid pulse width modulation (PWM) technique is introduced to control the buck-boost stage. Accordingly, the buck-boost stage of the 1P-CG-BBI operates similar to a conventional DC-DC boost converter in the positive half cycle. In the negative half cycle, this stage behaves as a traditional inverting DC-DC buck-boost converter. Accordingly, the DC-DC operation and DC-AC operation can be controlled, independently. Consequently, the modulation index can be significantly improved compared to previous CG inverters. High modulation index tends to reduce component voltage rating and increase system efficiency. A comparison study has been discussed to highlight these advantages. Simulation results conducted using PSIM software are considered to verify the operation of the proposed inverter. A laboratory prototype is also developed to further demonstrated the accuracy of theory. Accordingly, the proposed inverter obtains 93.12% and 91.83% efficiency at 550-W for buck and boost operating, respectively.