Evaluation of the ventilation system in an LNG cargo tank construction platform (CTCP) by the AHP-entropy weight method

Owing to the vulnerability of Invar to moisture in the membranes of LNG tanker cargo tank construction platforms(CTCPs),an energy-efficient ventilation system is needed to maintain a suitable thermal-moisture environment and a healthy workplace.However,the optimal distribution of supply and return devices that would guarantee worker satisfaction,air quality,and energy efficiency is unclear.Therefore,we conducted numerical simulations to determine the worker satisfaction indices(temperature,relative humidity,and carbon monoxide concentration satisfactions),air quality index(contaminant-removal efficiency),and energy efficiency index(heat-removal efficiency)with supply vane angles ranging from-75°to 0°and two return vent positions(the bottom return vent and the top return vent).The analytic hierarchy process(AHP)entropy weight method was employed to determine the optimal supply vane angle and return vent position for three design targets by considering these indices simultaneously.The results indicated that,with a supply angle of-45°and a bottom return vent,worker satisfaction and air quality were prioritized.Furthermore,a high energy performance of the ventilation system was achieved with a-15°supply angle and a bottom return vent.Moreover,a comprehensive graph of supply vane angles at both return heights,which could provide a reference for optimizing the ventilation system in LNG-CTCPs,is described.

Impact of the PV Location in Distribution Networks on Network Power Losses and Voltage Fluctuations with PSO Analysis

Increased grid integration of photovoltaic(PV)has aggravated the uncertainty of distribution network operations.For a distribution network with PV,the impact of the PV location on the network power losses and voltage fluctuations is investigated with analytical derivations reflected by the line impedance.Optimization approaches of the PV location with consideration of two aspects,i.e.,minimum network power losses and minimum voltage fluctuations,are analyzed.A particle swarm optimization(PSO)algorithm is used to synthesize an optimal compromised solution so as to determine the PV location.A 10 kV distribution network with one PV is established on the time-domain simulation environment PSCAD/EMTDC.The simulation results justify the theoretical analysis and indicate that when the active power of the PV is more/less than twice that of the overall loads/end loads,the network power losses and node voltage fluctuations are both minimum when the PV is integrated into the head/tail end of the network.When the active power of the PV is between the above two conditions,nodes t/f can be identified for the integration of the PV between the head/end nodes of the network to achieve the minimum network power losses/voltage fluctuations,respectively.The effectiveness of the proposed optimization approach is verified and can provide a reference for selecting the PV location in the distribution network.

Equivalent model of multi-type distributed generators under faults with fast-iterative calculation method based on improved PSO algorithm

There are various types of distributed generators (DGs) with different grid integration strategies. The transient characteristics of the fault currents provided by the DGs are different to those of conventional synchronous generators. In this paper, a distribution network with multi-type DGs is investigated, including consideration of DG low-voltage ride through (LVRT). The fault current characteristics of two typical DGs, i.e. an inverter-interfaced distributed generator (IIDG) and a doubly-fed induction generator (DFIG), are analyzed, considering the specific operation modes. Based on analysis of the fault characteristics, an equivalent model of the multi-type DGs under symmetrical/asymmetrical fault conditions is established. A fast-iterative fault calculation method for enhancing the calculation efficiency while avoiding local convergence is then proposed using an improved particle swarm optimization (PSO) algorithm. A simulation system of the distribution network with multi-type DGs is established in PSCAD/EMTDC. The simulation results validate the high accuracy and calculation efficiency of the proposed calculation method of the fault components. This can assist in the settings of the protection threshold.