Search Results (3)

When the shaft rotates in microturbines, the rotational movement is converted to electrical power. This is achieved through a permanent magnet synchronous machine (PMSM) housed on the shaft and the power electronics components. To the best of the authors’ knowledge, articles that comprehensively describe the power transmission and control in the electrical part of microturbines have yet to be introduced, namely, the PMSM and power electronics. This review paper presents a detailed review of power conversion in each component of the electrical part of microturbines. The paper also reviews the existing literature on microturbines’ electrical performance, noting areas where progress has already been made as well as those where more research is still needed. Furthermore, the paper explains the control system in the electrical part of microturbines, outlining the grid synchronisation control approach for grid-connected microturbines and reviews the possibility of employing control strategies that engage the PMSM and power electronics as controllers for certain variables in microturbines, such as the shaft rotational speed and torque. Such control methods are more crucial in externally fired microturbines since traditional control strategies used in internally fired microturbines, such as thermal input regulation, are no longer an option in externally fired microturbines for controlling the shaft speed. The significance of higher switching frequencies in power electronics is also discussed. The higher switching frequency, the faster response to load variations and, therefore, the more reliable the control system. A greater switching frequency allows for reduced power loss, cost, and unit size. In this context, it is recommended in this review paper that future research consider using silicon carbide switching devices rather than silicon ones, which is the current practice, to build up the microturbines converters’ topology. The recommendation was motivated by looking at the existing literature that compares the switching frequency, size, cost, thermal endurance, and power losses of silicon and silicon carbide components in applications other than microturbines since initiatives of using silicon carbide in microturbine power electronics have not been reported in the literature, as far as the authors are aware. The electrical components of microturbines account for a third of the entire size and cost of the unit. This means that reducing the size and cost of the electronics contributes effectively to reducing the total size and cost. In applications other than microturbines, silicon carbide exhibited promising results compared to silicon in terms of size and long-term cost. Investigating silicon carbide in microturbines is worthwhile to see if it provides such promising benefits to the microturbine unit. Full article

The development of AC distribution systems provides for the seamless integration of low-voltage microgrids with distributed energy resources (DERs). This poses new challenges for the control of normal, emergency, and post-emergency states of microgrids, calling for the creation and development of information and communications technology infrastructure. Power converters/inverters that are used to integrate renewable DERs lack inertia. Along with them, fossil fuel-fired generation units are also being integrated into microgrids. These include gas generator sets, diesel generator sets, and microturbines, having small (up to 1–2 s) values of mechanical inertia constants—Tj. This leads to an increase in the rate of transients by a factor of 5–10. Under these conditions, the technical requirements for the speed of automatic power flow control systems, as well as the methods they rely on, have to be reconsidered. Microgrids include DC microgrids, AC microgrids, and hybrid (AC-DC) microgrids. In the case of hybrid microgrids, DERs are connected to the DC grid and are integrated into the AC grid through a common inverter. The complexity of the task of microgrid control is due to the need to choose properly the type and extent of control actions so as to prevent the emergence and development of accidents. The employed control methods must ensure the reliable power supply to consumers and the quality of power in microgrids, as well as the reliable operation of the external distribution systems into which they are integrated. The article gives an overview of control methods for low-voltage AC and AC-DC microgrids, which allow one to tackle effectively solve the tasks. Full article

Trigeneration or combined cooling, heat and power (CCHP) systems fueled by raw biogas can be an interesting alternative for supplying electricity and thermal services in remote rural areas where biogas can be produced without requiring sophisticated equipment. In this sense, this study considers a performance analysis of a novel small-scale CCHP system where a biogas-fired, 5 kW_el externally fired microturbine (EFMT), an absorption refrigeration system (ARS) and heat exchangers are integrated for supplying electricity, refrigeration and hot water demanded by Bolivian small dairy farms. The CCHP solution presents two cases, current and nominal states, in which experimental and design data of the EFMT performance were considered, respectively. The primary energy/exergy rate was used as a performance indicator. The proposed cases show better energy performances than those of reference fossil fuel-based energy solutions (where energy services are produced separately) allowing savings in primary energy utilization of up to 31%. Furthermore, improvements in electric efficiency of the EFMT and coefficient of performance (COP) of the ARS, identified as key variables of the system, allow primary energy savings of up to 37%. However, to achieve these values in real conditions, more research and development of the technologies involved is required, especially for the EFMT. Full article