Calculation model for water influx and controlled reserves for CBM wells with high water yield

Compared with conventional gas reservoir,percolation mechanism of coalbed methane(CBM)is completely different,it is remarkably affected by adsorption/desorption performance,pressure variation and coalbed characteristics.Then it is difficult to calculate the controlled reserves of CBM wells.Moreover,the connection of edge-bottom water or interbedded water by fractures or faults may largely increase the water yield and drainage period,leading to obvious water invasion in some CBM wells.There are few literature about the predicted production for CBM wells with high water yield.Focusing on the unconventional CBM reservoir,methods of pseudo geological reserves and production index curves are adopted to establish the calculation model of water influx and controlled reserves.It further confirms that the calculation model is successfully applicated on the CBM wells at the middle part of Qinshui Basin in China.

A Review of State-of-the-art Flexible Power Point Tracking Algorithms in Photovoltaic Systems for Grid Support:Classification and Application

To maximize conversion efficiency,photovoltaic(PV)systems generally operate in the maximum power point tracking(MPPT)mode.However,due to the increasing penetra tion level of PV systems,there is a need for more developed control functions in terms of frequency support services and voltage control to maintain the reliability and stability of the power grid.Therefore,flexible active power control is a manda tory task for grid-connected PV systems to meet part of the grid requirements.Hence,a significant number of flexible pow er point tracking(FPPT)algorithms have been introduced in the existing literature.The purpose of such algorithms is to real ize a cost-effective method to provide grid support functional ities while minimizing the reliance on energy storage systems.This paper provides a comprehensive overview of grid support functionalities that can be obtained with the FPPT control of PV systems such as frequency support and volt-var control.Each of these grid support functionalities necessitates PV sys tems to operate under one of the three control strategies,which can be provided with FPPT algorithms.The three control strate gies are classified as:①constant power generation control(CP GC),②power reserve control(PRC),and③power ramp rate control(PRRC).A detailed discussion on available FPPT algo rithms for each control strategy is also provided.This paper can serve as a comprehensive review of the state-of-the-art FPPT algorithms that can equip PV systems with various grid support functionalities.

Adaptive Frequency Responsive Control for Wind Farm Considering Wake Interaction

With the increasing share of wind power,it is expected that wind turbines would provide frequency regulation ancillary service.However,the complex wake effect intensifies the difficulty in controlling wind turbines and evaluating the frequency regulation potential from the wind farm.We propose a novel frequency control scheme for doubly-fed induction generator(DFIG)-based wind turbines,in which the wake effect is considered.The proposed control scheme is developed by incorporating the virtual inertia control and primary frequency control in a holistic way.To facilitate frequency regulation in timevarying operation status,the control gains are adaptively adjusted according to wind turbine operation status in the proposed controller.Besides,different kinds of power reserve control approaches are explicitly investigated.Finally,extensive case studies are conducted and simulation results verify that the frequency behavior is significantly improved via the proposed control scheme.

Impact of blood pressure control on coronary flow reserve in hypertensive patients

Objective To investigate the impacts of blood pressure control on coronary flow reserve(CFR)in hypertensive patients.Methods A total of 236 patients without significant coronary stenosis(defined as<50%luminal narrowing confirmed by coronary angiography or coronary artery CT scan)between January 2011 and July 2015were retrospectively enrolled in this study.CFR