Search

Smart grid is a new type of power grid that integrates advanced information communication technology and measurement technology into conventional power grids. It provides an efficient and intellige...

This paper develops a decision-making model to assist the improvement of the carrying capacity of ship locks by combing fuzzy logic, the analytic hierarchy process (AHP) method, and the technique for order preference by similarity to an ideal solution (TOPSIS). A three-level hierarchical structure is constructed to identify the key factors influencing the carrying capacity of ship locks from the aspects of ship locks, vessels, environment, and administration. On this basis, a series of targeted strategies have been put forward to improve the carrying capacity of ship locks, and the TOPSIS method is applied to rank these strategies in terms of their performance. A case study of the five-stage dual-track ship lock of the Three Gorges Dam in China has been conducted to demonstrate the feasibility and rationality of the proposed model, and correlation analysis is conducted to verify the identified influencing factors in order to eliminate potential bias which may be generated from using AHP. The results obtained from the proposed methods are consistent with the real-life situation to a certain extent, indicating that the proposed method can provide a useful reference for improving the carrying capacity of ship locks.

This paper describes how authors examined the teaching practice of secondary vocational English writing, and learned that there were several problems with it, such as insufficient class instruction time for writing, students' anxiety about writing, the great emphasis placed on the result, the lack of interaction between students and teachers, and single evaluations of student's writing. To address these problems and account for the realistic conditions, the authors developed a WeChat official account and used it to conduct an Instruction of English writing experiment, hoping to improve the teaching effect. The English writing teaching method based on a WeChat Official Account in secondary vocational schools can raise students' interest in English writing, improve their writing ability, enhance vocabulary accumulation and application, raise the level of writing arrangement and strengthen the standardization of English writing application.

After establishing the Vienna rectifier mathematical model, we set the PID parameters through the intelligent algorithm to overcome the poor effect of the traditional voltage and current double closed loop PI controller when it encountered disturbance. In this paper, the single neuron adaptive PID controller is used to control the DC side voltage so that the output voltage can suppress the disturbance. The current inner loop uses a fuzzy-PI controller to control the current component in the dq coordinate system so that the current can quickly respond to disturbance when the load is disturbed and track the voltage of the grid.

This paper deeply analyzes and studies the ship path planning problem. An improved particle swarm optimization algorithm named chaos multi-population particle swarm optimization(CMPSO) is designed for ship path planning. Firstly, the marine environment model is established based on the link graph method, and the Dijkstra algorithm is used to plan the initial path; Secondly, the improved particle swarm algorithm is used for path planning, a multi-population mechanism is established to balance the population's global search ability and local search ability; Finally, simulate the initial path planning and global static path planning. The results show that the proposed algorithm has better performance than path planning algorithm based on linearly decreasing weight particle swarm optimization(LDW-PSO).

In order to improve the performance of the three phases PLL system, this paper designs an algorithm to optimize the PI controller parameters based on the integral of squared error theory. First, it analyzes the nonlinear character of the three phases PLL which uses the d-q coordinate transformation theory to lock the voltage phase, and deduces the closed loop transfer function of the PLL system with PI controller. In the second part, it analyzes the harmonic component of the voltage projected on q axis, and designs a reasonable filter to eliminate the effect of the harmonic voltage. With the linearizated closed loop transfer function, it establishes the cost function of the controller parameters optimization problem based on the ISE theory, and provides a rule that how to design the reference trajectory. For the cost function optimization, it deduces the partial derivative of the cost function and uses conjugate gradient method to solve the optimization problem. In the last part, it applies the optimized PI controller to unbalanced grid and voltage distortion conditions, the simulation results indicate that the optimized PI controller obtains robust and fast tracking ability.

In order to improve the dynamic performance of active magnetic bearing systems with highly nonlinear and naturally unstable dynamics, a new nonlinear fuzzy-immune proportional-integral-derivative (PID) controller is proposed by combining the immune feedback law with linear PID control. This controller consists of a PID controller and a basic immune proportional controller in cascaded connection, the nonlinear function of the immune proportional controller is realized by using fuzzy reasoning. Simulation results demonstrate that the active magnetic bearing system with the proposed controller has better dynamic performance and disturbance rejection ability than using the linear PID controller.