Electric propulsion ship secondary frequency control based on variable universe fuzzy method

[Objectives] This paper aims to solve the frequency fluctuation in a ship's power system caused by power disturbances.[Methods] To this end,a battery energy storage method is introduced to balance the output power and demand power,and the variable universe fuzzy method is utilized for the secondary frequency control of the ship's power system. In order to improve the control precision,area control error and change rate of the controller input,an incremental method is used to design a scaling factor that will expand or reduce the universe in case the control rule is unchanged.[Results] The simulation results show that a ship's power system which contains a battery can reduce the frequency fluctuation and make it stable in a short time.[Conclusions] Compared with the traditional fuzzy control, the proposed method offers better performance under external disturbances and parameter perturbation. The proposal in this paper can guarantee robust stability and robust performance

Ship Dynamic Positioning Systems Based on Fuzzy Predictive Control

Dynamic Positioning Systems (DPS) is a technique of automatically maintaining the position of vessels within the specified limits by controlling thrusters. This paper introduces a fuzzy predictive control to position vessels. Firstly, the mathematical model of vessel is created and simplified. Then, we use feed-forward compensation to decouple the system. The T-S model is identified by Fuzzy C-Means clustering algorithm and Least Squares method. After that, we use Generalized Predictive Control (GPC) to control the ships in three degrees of freedom (DOF)-surge, sway and yaw. The simulation results show that the fuzzy predictive control can orient the vessels effectively.  DOI: http://dx.doi.org/10.11591/telkomnika.v11i11.352

Feature Reduction for Power System Transient Stability Assessment Based on Neighborhood Rough Set and Discernibility Matrix

In machine learning-based transient stability assessment (TSA) problems, the characteristics of the selected features have a significant impact on the performance of classifiers. Due to the high dimensionality of TSA problems, redundancies usually exist in the original feature space, which will deteriorate the performance of classification. To effectively eliminate redundancies and obtain the optimal feature set, a new feature reduction method based on neighborhood rough set and discernibility matrix is proposed in this paper. First, 32 features are selected to structure the initial feature set based on system principle. An evaluation index based on neighborhood rough set theory is used to characterize the separability of classification problems in the specified feature space. By constructing the discernibility matrix of input features, a feature selection strategy is designed to find the optimal feature set. Finally, comparative experiments based on the proposed feature reduction method and several common feature reduction techniques used in TSA are applied to the New England 39 bus system and Australian simplified 14 generators system. The experimental results illustrate the effectiveness of the proposed feature reduction method

Differential Evolution-Based Load Frequency Robust Control for Micro-Grids with Energy Storage Systems

In this paper, the secondary load frequency controller of the power systems with renewable energies is investigated by taking into account internal parameter perturbations and stochastic disturbances induced by the integration of renewable energies, and the power unbalance caused between the supply side and demand side. For this, the μ-synthesis robust approach based on structure singular value is researched to design the load frequency controller. In the proposed control scheme, in order to improve the power system stability, an ultracapacitor is introduced to the system to rapidly respond to any power changes. Firstly, the load frequency control model with uncertainties is established, and then, the robust controller is designed based on μ-synthesis theory. Furthermore, a novel method using integrated system performance indexes is proposed to select the weighting function during controller design process, and solved by a differential evolution algorithm. Finally, the controller robust stability and robust performance are verified via the calculation results, and the system dynamic performance is tested via numerical simulation. The results show the proposed method greatly improved the load frequency stability of a micro-grid power system

Epitaxial Crystallization Behavior of Poly(butylene adipate) on Orientated Poly(butylene succinate) Substrate

The crystallization behavior of poly(butylene adipate) (PBA) in the sheared PBS/PBA blend, as well as on highly orientated poly(butylene succinate) (PBS) substrate, was studied by means of DSC, POM, Raman microscopy, and XRD. The results showed that the pre-existing orientated PBS crystals exhibit a very strong nucleation ability toward PBA as reflected by the increased crystallization temperature and the occurrence of heteroepitaxy and transcrystallization of PBA on the PBS substrate. The epitaxial crystallization of PBA on the PBS substrate results in the formation of α-form PBA crystals in any crystallization conditions