Organic Rankine Cycle (ORC) based small-scale energy generation systems can be utilized to address the rapidly increasing demand for low-cost power. But the overall efficiency of these systems is limited by the efficiency of the gas expander which extracts work from the working fluid. This efficiency can be greatly improved by regulating the flow of working fluid into the expander chamber using a control valve. In this manuscript, a rotary valve driven by a direct drive stepper motor (DDRV) is proposed and the dynamics of the valve is studied. The overall performance of the limaçon expander equipped with this valve on the inlet port is also analyzed. The thermodynamic performance of the system such as isentropic efficiency and filling factor are calculated. An increase in isentropic efficiency of 14.86% with a decrease in filling factor of 16.88% is achieved compared to the ported, without an inlet valve, expander.
Energy usage optimal scheduling has attracted great attention in the power system community, where various methodologies have been proposed. However, in real-world applications, the optimal scheduling problems require reliable energy forecasting, which is scarcely discussed as a joint solution to the scheduling problem. The 5 th IEEE Computational Intelligence Society (IEEE-CIS) competition raised a practical problem of decreasing the electricity bill by scheduling building activities, where forecasting the solar energy generation and building consumption is a necessity. To solve this problem, we propose a technical sequence for tackling the solar PV and demand forecast and optimal scheduling problems, where solar generation prediction methods and an optimal university lectures scheduling algorithm are proposed.
This paper compares the electromagnetic torque produced in generic multiphase trapezoidal back EMF permanent magnet machines when using sinusoidal and rectangular current excitations. It is known that sinusoidal currents can produce the same average torque with less current compared to rectangular currents in three phase variants of this machine. Numerical analysis of the torque harmonics is used in this paper to compare sinusoidal and rectangular current excitations in these machines with a larger number of phases. It is shown that sinusoidal current excitation provides superior performance for prime phase numbers and rectangular current excitation remains suitable for triplen phase numbers beyond three.
Grid-connected AC/DC power converters play a crucial role in integrating renewable energies, smart grids, and motor drives. Consequently, high-performance control techniques have constantly attracted the interest of researchers. Predictive direct power control (P-DPC) strategies are promising control techniques for these converters, due to their fast transient response. However, standard P-DPC strategies cannot effectively compensate for steady-state errors when the switching frequency is reduced, due to model inaccuracies. This work proposes a new optimal switching sequence direct power control (OSS-DPC) strategy, which enhances the converter discrete-time model by estimating the grid currents and voltages at each commutation instant within a sampling period. As a result, the proposed OSS-DPC provides a fast dynamic response with reduced overshoot and improved steady-state performance, outperforming the standard P-DPC strategies.
Electromagnetic Compatibility (EMC) has gained an evident importance with the evolution and optimization of power electronics and power systems. With the ease of access to a variety of power converters to be used in our daily life, the EMC standardization is a growing concern. This study compares and evaluates the conducted Electromagnetic Interference (EMI) performance of some off-the-shelf power supplies using pre-compliance EMC testing facility. Furthermore, the results are verified with a calibrated EMC facility and evaluated under AS/NZS 61000.6.3. Various insights are highlighted which are important to consider whilst moving towards the realization of EMC in power electronics.
