System Modeling and Optimal Dispatching of Multi-energy Microgrid with Energy Storage

The coordinated operation and comprehensive utilization of multi-energy sources require systematic research.A multi-energy microgrid(MEMG)is a coupling system with multiple inputs and outputs.In this paper,a system model based on unified energy flows is proposed to describe the static relationship,and an analogue energy storage model is proposed to represent the time-dependency characteristics of energy transfer processes.Then,the optimal dispatching model of an MEMG is established as a mixed-integer linear programming(MILP)problem using piecewise linear approximation and convex relaxation.Finally,the system model and optimal dispatching method are validated in an MEMG,including district electricity,natural gas and heat supply,and renewable generation.The proposed model and method provide an effective way for the energy flow analysis and optimization of MEMGs.

Virtual Conductance Based Cascade Voltage Controller for VSCs in Islanded Operation Mode

Voltage source converters have become the main enabler for the integration of distributed energy resources in microgrids.In the case of islanded operation,these devices normally set the amplitude and frequency of the network voltage by means of a cascade controller composed of an outer voltage control loop and an inner current control loop.Several strategies to compute the gains of both control loops have been proposed in the literature in order to obtain a fast and decoupled response of the voltages at the point of common coupling.This paper proposes an alternative and simple methodology based on the introduction of a virtual conductance in the classic cascade control.This strategy allows to design each control loop independently,obtaining a closed-loop response of a first-order system.In this way,the gains of each control loop are easily derived from the parameters of the LC coupling filter and the desired closed-loop time constants.Furthermore,a state observer is included in the controller to estimate the inductor current of the LC filter in order to reduce the number of required measurements.A laboratory testbed is used to validate and compare the proposed controller.The experimental results demonstrate the effectiveness of the proposal both in steady-state and transient regimes.

Nanophotonic-structured front contact for high-performance perovskite solar cells

We report the design of a nanophotonic metaloxide front contact aimed at perovskite solar cells(PSCs)to enhance optoelectronic properties and device stability in the presence of ultraviolet(UV)light.High-quality Cr-doped ZnO film was prepared by industrially feasible magnetron sputter deposition for the electron transport layer of PSCs.As a means,the influence of the Cr content on the film and device was systematically determined.In-depth device optics and electrical effects were studied using advanced three-dimensional opto-electrical multiphysics rigorous simulations,optimizing the front contact for realizing high performance.The numerical simulation was validated by fabricating PSCs optimized to reach high performance,energy conversion efficiency(ECE)=17.3%,open-circuit voltage(V_(OC))=1.08 V,short-circuit current density(J_(SC))=21.1 mA cm^(-2),and fillfactor(FF)=76%.Finally,a realistic front contact of nanophotonic architecture was proposed while improving broadband light absorption of the solar spectrum and light harvesting,resulting in enhanced quantum efficiency(QE).The nanophotonic PSC enables J_(SC)improvement by~17%while reducing the reflection by 12%,resulting in an estimated conversion efficiency over 23%.It is further demonstrated how the PSCs’UV-stability can be improved without considerably sacrificing optoelectronic performances.Particulars of nanophotonic designed ZnO:Cr front contact,PSCs device,and fabrication process are described.