Current Issue : April - June Volume : 2019 Issue Number : 2 Articles : 5 Articles
This paper introduces novel approaches to the predictive control of a DC-DC boost\nconverter and a comparison of the controllers built that consider all of the current objectives and\nminimize the complexity of the online processing. The primary concern is given to the applicability\nof the inclined methods for systems that are physically small but considered physically fast processes.\nAlthough the performed methodologies are simulated and applied to a DC-DC boost converter,\nthey can have broader applicability for different switched affine systems as a subgroup of the hybrid\nsystems. The introduced methods present an alternative way of building the process model based\non the fuzzy identification that contributes to the final objective: the applicability of the predictive\nmethods for fast processes....
The high-power density and capability of three-port converters (TPCs) in generating\ndemanded power synchronously using flexible control strategy make them potential candidates for\nrenewable energy applications to enhance efficiency and power density. The control performance of\nisolated TPCs can be degraded due to the coupling and interaction of power transmission among\ndifferent ports, variations of model parameters caused by the changes of the operation point and\nresonant peak of LC circuit. To address these issues, a linear active disturbance rejection control\n(LADRC) system is developed in this paper for controlling the utilized TPC. A virtual damping based\nmethod is proposed to increase damping ratio of current control subsystem of TPC which is beneficial\nin further improving dynamic control performance. The simulation and experimental results show\nthat compared to the traditional frequency control strategy, the control performance of isolated TPC\ncan be improved by using the proposed method....
In order to realize further stability of a stack-type thermoelectric power generating\nmodule (i.e. no electrical connections inside), flexible materials of\nmetal springs and/or rods having restoring forces were installed between\nlower-temperature-sides of thermoelectric elements. These flexible materials\nwere expected to play three important roles of interpolating different thermal\nexpansions of the module components, enlarging heat removal area and penetration\nof any media through themselves. Then, a low-boiling-point medium\n(i.e. NOVEC manufactured by 3M Japan Ltd.) was also applied for a\nhigh-speed direct heat removal via its phase change from the lower-\ntemperature-sides of the thermoelectric elements in the proposing\nstack-type thermoelectric power generating module. No electrical disconnections\ninside the module were confirmed for more than 9 years of use, indicating\nfurther module stability. The power generating density was improved\nto about 120 mWâ?¢m-2 with SUS304 springs having 0.7 mm diameter. Increasing\npower generating density can be expected in terms of suitable selection\nof flexible metal with high Vickers hardness , cavities control on the\nspring surface, more vigorous multiphase flow with adding powders to the\nmedium and optimization of the module configurations according to numerical\nsimulations....
Improper connections of unbalanced distributed generators (DGs) and loads in a\nthree-phase microgrid cause unbalanced and bidirectional power flow problems. The unbalanced\nDGs and loads may also aggravate the electric power quality (EPQ), such as voltage regulation,\npower factor, and unbalanced current and voltage. This increases the difficulty of operation in\na microgrid. In this study, a three-phase, delta-connected, shunt-type universal compensator\nwas employed for achieving the bidirectional power-flow balancing and improving the EPQ\nof a three-phase, distribution-level microgrid with unbalanced DGs and loads. A feedforward\ncompensation scheme was derived for the compensator by using the symmetrical components\nmethod. In practical applications, the universal compensator can be implemented as static var\ncompensators (SVCs), static synchronous compensators (STATCOMs), or an additional function\nof active filters. With the on-line compensation of the proposed compensator, the bidirectional\npower-flow balancing and EPQ improvement in the microgrid were achieved. A demonstration\nsystem was proposed to present the effectiveness of the compensator....
For the development of distributed power supply active distribution network\nsystem, the instability of the power supply side causes the system frequency to\nbe disturbed, and harmonics, voltage fluctuations, or ferromagnetic saturation\ncauses resonance and other series of power quality problems; what resulting\nin the over-voltage and over-current can easily damage components\nand threaten the system's safe and stable operation. In order to solve these\nproblems, this paper compares some harmonic detection and filtering methods,\ndevices and methods for suppressing resonance in recent years, and\ncombines the principle of resonance to design a nonlinear inductive circuit\nthat can suppress resonant overcurrent according to the characteristics of\nnonlinear inductors. Compared with the Resistance (R) series Induct Capacitance\n(LC) parallel circuit composed of common inductors, the circuit described\nin this paper is not affected by overcurrent, and the influence of\novervoltage is relatively greatly reduced. The simulate-on proves that this\ncircuit suppresses the effects of resonant overvoltage and overcurrent....
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