Research and comprehensive evaluation on delivery schemes of the Grand Inga hydropower station

Congo River has abundant hydropower resources,and large-scale cascade power stations,such as the Grand Inga,can be constructed in downstream locations.However,the fragile economic foundations of the Democratic Republic of the Congo and neighbor!ng Central African countries,and the small-scale regional power consumption market prohibit the implementation of large-scale hydro power projects.As the high-voltage,I on g-dista nee power transmission tech no logy matures,hydropower from the Grand Inga can be delivered to load centers in other regions of Africa.This study establishes a 6 dime nsional comprehe nsive assessment model using the best-worst method to evaluate large-scale,I on g-distance,cross-border power intercon necti on projects.The model is applied to evaluate all the can didate in ter-regional power delivery schemes of the Inga III hydropower station,and the evaluation results can effectively help investment institutions and policy makers in policy making and potential market targeting.

An Integrated Control Strategy Adopting Droop Control with Virtual Inductance in Microgrid

As there exists sorts of distributed generators in microgrid, an integrated control strategy containing different control methods against corresponding generators should be applied. The strategy in this paper involves PQ control and droop control methods. The former aims at letting generators like PV output maximum power. The latter stems from inverter parallel technique and applies to controlling generators which can keep the network voltage steady to make the parallel system reach the minimum circulation point. Due to the unworthiness of droop control applied in low-voltage microgrid of which the impedance ratio is rather high, the paper adopts the droop control introducing virtual generator and virtual impedance. Based on theoretical analysis, simulation in Matlab is also implemented to verify the feasibility of the strategy.

Simulation on Calculation Accuracy of Three Methods for Live Line Measuring the Parameters of Transmission Lines with Mutual Inductance

Live line measurement methods can reduce the loss of power outages and eliminate interference. There are three live line measurement methods including integral method, differential method and algebraic method. A simulation model of?two coupled parallel transmission lines spanning on the same towers is built in PSCAD and the calculation errors of these three methods are compared with different sampling frequencies by using of Matlab. The effect of harmonic on calculation is also involved. The simulation results indicate that harmonic has the least effect on the algebraic method which provides stable result and small error.

New Method of Measuring the Positive-sequence Capacitance of T-connection Transmission Lines

A novel method of measuring the positive-sequence capacitance of T-connection transmission lines is proposed. The mathematical model of the new method is explained in detail. In order to obtain enough independent equations, three independent operation modes of T-connection transmission lines during the line measurement are introduced. The digital simulation results and field measurement results are shown. The simulation and measurement results have validated that the new method can meet the needs of measuring the positive-sequence capacitance of T-connection transmission lines. This method has been implemented in the newly developed measurement instrument.

Models for economic evaluation of multi-purpose apple harvest platform and software development

An increasing number of U.S.apple growers are now interested in using harvest platforms to increase harvest productivity,expand labor pool,and alleviate tough working conditions.To maximize benefits,functions of thinning,pruning&training,and infield sorting have been or are to be incorporated into harvest platforms.Though growers are most concerned with economic benefits,few cost-benefit studies had been conducted on different platforms.In the meantime,economic analysis procedure is complex and each analysis is for one specific machine(not for general purposes).No software has been developed as a general and ready-to-use tool for growers and researchers for the platform economic analysis.In this study,platforms,both available on the marketplace and developed in lab as pilot trials,were reviewed.Costs and benefits models were then established,based on which multi-purpose apple harvest platform economic evaluation software(iMPAHP)was developed(capable of evaluating a wide variety of apple harvest platforms).A case study(machine cost of$100000,accommodating 6 workers,processing apple incidence of 10%with 90%sort-out rate,and harvest,thinning,and pruning&training productivity increase by 40%,50%,and 60%,respectively)based on iMPAHP demonstrated that infield sorting,harvest,thinning,and pruning and training accounted for 48.4%,23.9%,14.3%,and 13.4%of the total benefits,respectively.In the case that the platform was in all-four-purpose-application,the net present value(NPV)analysis of a 10-year investment showed a positive return of$60547.However,without infield sorting function,the NPV resulted in a negative value,indicating a loss for the machine investment.Though incorporating the modular infield sorting system certainly increased the overall machine investment by$30000,the benefits outweighed the costs.