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In this paper, a new topology for cascaded multilevel inverter based on Quasi-Zsource converter is proposed. In the proposed topology the magnitude of output DC voltage is not limited to the sum of magnitude of DC voltage sources. Moreover, the reliability of the circuit due to capability of short circuit by Z-Source network is increased. The Quasi-Zsource converter in different modes is analyzed and the voltage gain is obtained. Also, the values of Quasi-Z-Source network components are designed. In the proposed topology, the number of DC voltage sources, the number of switches, installation area and cost in comparison with conventional multilevel inverters are significantly reduced. Three algorithms to determine the magnitude of DC voltage sources are proposed. Then the optimal structures for the minimum number of switches and DC voltage sources to generate the maximum voltage levels are presented. Moreover, the control method for the proposed topology is described. To verify the performance of the proposed topology, simulation and experimental results of proposed topology are presented.

There is an increasing demand for low-cost single-phase DC– AC inverters in many applications such as PV systems. These systems may be used without the transformer to improve efficiency and make the whole system lighter, smaller, and easier to install. With the transformerless topology, the system efficiency may be increased by about 2%, and the related cost may be decreased by about 25%. There are large leakage currents in transformerless topologies, especially in photovoltaic systems, where safety issues and electromagnetic interference problems often occur. To overcome such disadvantages, common-ground topologies can be used as they can minimize the leakage current of the transformerless inverter ones. The transformerless semi-Quasi-Z-Source inverter (SqZS) with the common-ground structure offers many advantages over conventional single-phase inverters. Leakage current elimination, higher power density, fewer components, and low-cost features make it an attractive option as a micro-inverter in photovoltaic applications. The basic topology of SqZSI is especially suitable for a PV module in low-voltage applications as a low-cost micro-inverter with high-voltage SiC switching devices. However, the unity voltage gain is one of the disadvantages of SqZS inverters, which is referred to as a drawback. In other words, the conventional structure of SqZS is not capable of stepping up the voltage, and the maximum amplitude of AC voltage that can be extracted is equal to the input DC voltage. This paper proposes a modified structure for single-phase inverters (MSqZS) to achieve voltage boost capability. The voltage boost is achieved in a single-stage conversion just by adding an additional series DC blocking capacitor to the basic inverter. It also maintains the common-ground feature. Nonlinear sinusoidal modulation (NLSPWM) is modified to allow the SqZS basic structure to achieve high voltage gain. Although the proposed inverter is modified in topology and modulation, it is not more complex than the basic SqZSI. The proposed inverter has the least number of components among the similar step-up common-ground topologies. In this paper, the closed-loop control is proposed to improve the performance of the MSqZS under variable input voltage, as well as output load and compensation for the undesired and non-ideal effect of the parasitic elements. In addition, the proposed inverter is capable of generating reactive power. Also, the design consideration for series capacitor is analysed for proper capacitor selection. The simulation and experimental results under various closed-loop and open-loop scenarios comply with the IEEE Std 1547 and verify the appropriate performance of the proposed inverter.

Let R be a commutative ring with non-zero identity and M be a unitary R-module. Then the concept of Quasi-secondary submodules of M is introduced and some results concerning this class of submodules is obtained.

In this paper we extend the concepts of two sided ideal and right Quasi-duo ring. These ideals and rings are called totally fully in-variant and right strongly Quasi-duo, respectively. Right strongly Quasi-duo rings are always right Quasi-duo. We investigate the properties of these rings and ideals and show among other things that right strongly Quasi-duo rings are classical, directly finite and co-hopfian while right Quasi duo, right duo or commutative rings do not have necessarily these properties.

In this paper we introduce the notion of classical Quasiprimary submodules that generalizes the concept of classical primary submodules. Then, we investigate decomposition and minimal decomposition into classical Quasi-primary submodules. In particular, existence and uniqueness of classical Quasi-primary decompositions in finitely generated modules over Noetherian rings are proved. Moreover, we show that this decomposition and the decomposition into classical primary submodules are the same when Ris a domain with dim (R) £1.

We introduce Quasi-cofaithful ideals which are a generalization of cofaithful ideals, and investigate their properties. We hold that a faithful ideal I is Quasi-cofaithful if I contains a finitely generated faithful ideal I1. We show that every faithful ideal of R is Quasicofaithful if and only if every faithful ideal of Mn (R) is Quasi-cofaithful. Also we show that if R has the descending chain condition on right annihilators of right ideals, then each faithful ideal of R is Quasi-cofaithful. For a u.p.-monoid M, it is shown that if R is a Quasi-Baer ring, then each faithful ideal of R is Quasi-cofaithful if and only if each faithful ideal of the monoid ring R[M] is Quasi-cofaithful.