Stochastic Linear Programming for Optimal Planning of Battery Storage Systems Under Unbalanced-uncertain Conditions

Battery energy storage system(BESS)has already been studied to deal with uncertain parameters of the electrical systems such as loads and renewable energies.However,the BESS have not been properly studied under unbalanced operation of power grids.This paper aims to study the modelling and operation of BESS under unbalanced-uncertain conditions in the power grids.The proposed model manages the BESS to optimize energy cost,deal with load uncertainties,and settle the unbalanced loading at the same time.The three-phase unbalanced-uncertain loads are modelled and the BESSs are utilized to produce separate charging/discharging pattern on each phase to remove the unbalanced condition.The IEEE 69-bus grid is considered as case study.The load uncertainty is developed by Gaussian probability function and the stochastic programming is adopted to tackle the uncertainties.The model is formulated as mixed-integer linear programming and solved by GAMS/CPLEX.The results demonstrate that the model is able to deal with the unbalanced-uncertain conditions at the same time.The model also minimizes the operation cost and satisfies all security constraints of power grid.

Evolution of Single-Phase Power Converter Topologies Underlining Power Decoupling

Single-phase power converters are widely used in electric distribution systems under 10 kilowatts,where the second-order power imbalance between the AC side and DC side is an inherent issue.The pulsating power is decoupled from the desired constant DC power,through an auxiliary circuit using energy storage components.This paper provides a comprehensive overview of the evolution of single-phase converter topologies underlining power decoupling techniques.Passive power decoupling techniques were commonly used in single-phase power converters before active power decoupling techniques were developed.Since then,active power decoupling topologies have generally evolved based on three streams of concepts:1)current-reference active power decoupling;2)DC voltage-reference active power decoupling;and 3)AC voltage-reference active power decoupling.The benefits and drawbacks of each topology have been presented and compared with its predecessor,revealing underlying logic in the evolution of the topologies.In addition,a general comparison has also been made in terms of decoupling capacitance/inductance,additional cost,efficiency and complexity of control,providing a benchmark for future power decoupling topologies.

A Numerical Study of Characteristic Slow-Transient Behavior of a Compressible 2D Gas-Liquid Two-Fluid Model

The purpose of this paper is to gain some insight into the characteristic behavior of a general compressible two-fluid gas-liquid model in 2D by using numerical computations.Main focus is on mass transport phenomena.Relatively few numerical results in higher dimensions can be found in the literature for this two-fluid model,in particular,for cases where mass transport dynamics are essential.We focus on natural extensions to 2D of known 1D benchmark test cases,like water faucet and gas-liquid separation,previously employed by many researchers for the purpose of testing various numerical schemes.For the numerical investigations,the WIMF discretization method introduced in[SIAM J.Sci.Comput.26(2005),1449]is applied,in combination with a standard dimensional splitting approach.Highly complicated flow patterns are observed reflecting the balance between acceleration forces,gravity,interfacial forces,and pressure gradients.An essential ingredient in these results is the appearance of single-phase regions in combination with mixture regions(dispersed flow).Solutions are calculated and shown from early times until a steady state is reached.Grid refinement studies are included to demonstrate that the obtained solutions are not grid-sensitive.