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A two-stage hybrid isolated dc-dc boost converter for high power and wide input voltage range applications is proposed. It can be used as a front-end dc-dc converter that can boost variable low voltage from a power source (battery (home/industrial inverter/industrial UPS application), fuel-cell or solar-PV) and interface it to a high-voltage dc-ink, which typically feeds an inverter. A detailed comparison among the different family of converter topologies for isolated dc-dc boost application is carried out that can prove to be useful for power electronics engineers to choose the correct topology for a given input voltage range. The quantitative comparison takes into account the power device utilization, transformer utilization, capacitance utilization and inductive energy requirement. Based on the comparison, it is shown that with input voltage variation greater than 20%, two-stage hybrid isolated dc-dc boost converter is superior compared to other family of converters. Design details for the two stage converter are provided. The converter is developed and tested for a 5 KW inverter application with an input dc voltage range of 90-170 V and output ac voltage of 230 V. Theoretical analysis for loss calculations is also provided which closely matches the experimental results.

The circulating current and the large energy storage requirement are the two major limitations of the modular multilevel converter (MMC). The circulating current in MMC is majorly, in addition to the dc current, second harmonic in nature. If not controlled properly, it results in reduced efficiency and/or increased energy storage requirement (ESR). To enhance the efficiency, the second and the higher-order harmonic components in the circulating current of MMC are required to be suppressed. On the other hand, controlling the circulating current to have predefined magnitude and phase-angle can reduce the ESR. There are many control methods available in literature to suppress and also, to control the second harmonic circulating current (SHCC). These methods are mainly based on sensing the arm current and calculating the SHCC and then suppressing or controlling it based on the set objectives. In this paper, two control schemes are proposed to suppress the SHCC and to reduce the ESR. The proposed schemes are based on utilizing the instantaneous voltage signals of the sub-module capacitors in MMC. Hence, the sensing and communicating the sensed signal of arm currents can be avoided using the proposed schemes, which increases the reliability and leads to reduced cost and complexity. The efficacy of the proposed control schemes is verified using the simulation studies and also by using the scaled-down lab prototype of a 3-phase 7-level MMC.

Adefining component that makes the Journal of Emerging and Selected Topics in Power Electronics (JESTPE) a predominant publication in the field of power electronics is our past and current associate editors. Although they are largely hidden and unheard until papers they recommend for publication appear in print, the efforts of our associate editors are extremely important in producing the JESTPE for the readers. The tasks of an associate editor include reading the submissions, finding competent reviewers, reading the comments from the reviewers, and making recommendations to the assigned editors, all of which are to be accomplished in a timely manner. In some cases, associate editors expend lots of time contacting busy reviewers to submit their comments, making recommendations, and addressing rejected paper complaints from the authors.

The parallel-hybrid converter (PHC) is a promising high-power topology. Smaller capacitor size, lower capacitor and switch counts, and low-energy storage requirement are some of its important features. However, it requires a large dc-filter inductor to filter the dc-side harmonics. Moreover, since its dc and ac sides are strongly coupled, only a single stable operating point in terms of a fixed modulation-index (MI) value is possible. Even with an additional dedicated control effort, the obtained MI variation remains still limited. This article proposes the PHC-static compensator (STATCOM) configuration that eliminates the dc-filter inductor requirement and can also operate at any MI value without necessitating additional control efforts. A detailed power analysis of the PHC-STATCOM for balanced and unbalanced grid conditions (UGCs) is performed in this article. A new control technique for PHC-STATCOM is proposed, which effectively balances the capacitor voltages of its chain-links even during UGCs. The energy storage requirement of PHC-STATCOM is evaluated to obtain the capability curve and determine its capacitor size. The PHC-STATCOM is compared with the popular STATCOM configurations in terms of the capacitor and switch counts. The proposed principles of PHC-STATCOM for several three-phase balanced and UGCs are verified using simulation and experimental studies.

Recently, the idea of combining both thyristors and IGBTs in a voltage-source converter (VSC) structure has gained significant research interests for HVDC applications. The main objectives of deriving these topologies are to achieve forced-commutation of thyristors, increased efficiency, reduced energy-storage requirement and dc-fault tolerance besides retaining the VSC control flexibility. A novel topology named ‘thyristor-augmented modular bridge converter’ (TAMBC) is proposed in this paper. Each TAMBC phase contains four chain-links comprising of series-connected stacks. Each stack contains a parallel connection of an IGBT-based submodule-branch and a thyrsitor-branch. A control technique is developed that allows the main current to flow primarily through the thyrsitor-branch to achieve higher efficiency. In each phase of TAMBC, two chain-links generate the required ac voltage in the first half-cycle and are bypassed through thyrsitor-branch during the next half-cycle. Consequently, it enables current distribution among the chain-links resulting in reduced capacitors size and enhanced efficiency. The ability of TAMBC-HVDC systems to function over a wide operating range, to ride-through ac faults and to provide independent active and reactive power control are verified using PSCAD. Capacitors design, loss analysis and comparative evaluations are carried out to highlight the key features of the TAMBC over the existing ones.

The higher cost of silicon carbide (SiC) devices is a limiting factor for their utilization in power electronic applications. This has led to the development of hybrid topologies by combining both silicon (Si) and SiC devices. This article proposes such Si/SiC devices-based split-output hybrid active neutral-point-clamped (S-HANPC) converter topology for medium-voltage applications. The proposed S-HANPC topology mitigates the shoot-through fault current and also provides protection against the crosstalk related issues for the SiC mosfet s. Moreover, the strategically selected switching states in the modulation scheme of the S-HANPC topology optimize the loss distribution among the Si/SiC devices resulting in high efficiency. The split-inductors in the S-HANPC topology limit the overcurrent stress on the SiC switches and provides lower dv / dt in its output voltage without affecting its dynamic performance. In this article, the analytical method to calculate the optimal value of the split-inductors is given. Furthermore, it provides an investigation of the shoot-through fault current and losses in the converter switches. The effect of dead-time between the SiC switches on their switching performance is also analyzed using the experimental results of the double pulse test. The simulations and experimental results of the designed prototype validate the advantages of the topology.

Modular multilevel converter (MMC) is a preferred topology for higher power applications. The instantaneous voltage mismatch between the phase legs and dc bus in MMC leads to predominantly second-harmonic circulating current (CC). The sizes of submodule (SM) capacitor and arm inductor, power losses and current rating of semiconductor switches in MMC are influenced by the CC. This article proposes a circulating current optimization control (CCOC) scheme for MMC, which reduces the arm current peak value without increasing the SMs capacitors size for the same maximum voltage ripples. It enables the MMC to handle more power with the same rated switches. This controller works on the principle of controlling the amplitude and phase angle of CC to follow their respective optimized references. A detailed design and implementation method of CCOC is presented for all possible operating conditions of MMC in terms of modulation indices and load power factors. A comparative evaluation performed between CCOC and other major CC control schemes highlights its main features. The efficacy of the proposed scheme is validated using simulations and also using experimental studies on a seven-level three-phase grid-connected MMC prototype. The results demonstrate the effectiveness of the CCOC scheme and verify the proposed principles.

The purpose of this study was to find the factors responsible for winning in the men’s and women’s beach volleyball championship. Materials and methods. The study sample consisted of a total of 212 matches for men and 214 matches for women of the 2017 & 2019 FIVB Men and Women Beach Volleyball World Championships held at Vienna & Hamburg from 28 July to 6 Aug 2017 and 28 June to 7 July 2019. The matches were played by 192 teams (both men and women combined) consisting of 384 numbers (both men and women combined) of players from different nations. The data were analyzed using Binary Logistic Regression (Forward: LR Method) with the result of the game as the dependent variable and predictor variables as covariates. β, standard error β, Wald’s χ2, odds ratio with 95% confidence interval were calculated. Model evaluation was conducted using the likelihood ratio test, Cox & Snell (R2), and Nagelkerke (R2) tests. The goodness of fit test for the models was conducted using the Hosmer & Lemeshow test. Results. The analysis revealed seven factors related to winning in men’s and women’s competition. While in league rounds, six factors in men’s and seven factors in women’s competition were related to winning. Besides, in knockout rounds, four factors in men’s and six factors in women’s competition were related to winning. Conclusion. The study shows that there is a significant association of important factors with respect to winning a match in an elite beach volleyball championship. The coaches and players can take note of the important factors responsible for winning in the elite beach volleyball championship, with different factors playing an important role in men’s and women’s competition during league and knockout rounds as well.