A Review on Primary and Secondary Controls of Inverter-interfaced Microgrid

The demand of electricity and environmental issues associated with conventional power generation plants are increasing significantly.Modern technology has transformed the conventional power system through the integration of distributed generation(DG).With the help of modern power electronic technology,the conventional power system is able to support the integration of DGs based on renewable energy sources(RESs).The systematic combination of DGs with energy storage system forms a microgrid(MG),which can operate in islanded mode or grid-connected mode.The intermittent nature of RES and varying load pose substantial obstacles such as voltage and frequency instability,and the unreliability of RES.Unequal feeder impedances and non-linear loads are considered as present challenges in MG control.Hierarchical control has been useful in undertaking solutions to these issues.This paper covers the deep insight of different control methods applied at the primary and secondary control levels in hierarchical control.In primary control,the classification based on droop and non-droop controls is discussed.The virtual synchronization machine(VSM)based control method is reviewed.Voltage and frequency restoration control and economical operations at decentralized and centralized secondary control are analyzed in detail.Based on the existing literature,critical discussion on MG control and future trends are also presented to provide future research perspectives.

Review: Enhancing power transfer capability through flexible AC transmission system devices: a review

Global demand for power has significantly increased, but power generation and transmission capacities have not increased proportionally with this demand. As a result, power consumers suffer from various problems, such as voltage and frequency instability and power quality issues. To overcome these problems, the capacity for available power transfer of a transmission network should be enhanced. Researchers worldwide have addressed this issue by using flexible AC transmission system （FACTS） devices. We have conducted a comprehensive review of how FACTS controllers are used to enhance the avail- able transfer capability （ATC） and power transfer capability （PTC） of power system networks. This review includes a discussion of the classification of different FACTS devices according to different factors. The popularity and applications of these devices are discussed together with relevant statistics. The operating principles of six major FACTS devices and their application in increasing ATC and PTC are also presented. Finally, we evaluate the performance of FACTS devices in ATC and PTC improvement with respect to different control algorithms.

Adaptive control systems for dual axis tracker using clear sky index and output power forecasting based on ML in overcast weather conditions

The use of artificial intelligence in renewable energy systems increases energy generation and improves energy system management.The control system of many solar trackers is designed for maximum radiation power conditions and shows decent performance indicators,but during rapidly changing weather conditions or cloudy days,the performance of the solar trackers is reduced due to moving parts and low irradiance.Some studies show that the horizontal configuration produces more energy with scattered solar radiation than solar tracking sys-tems.This work shows the possibility of using solar tracking systems under different weather conditions and cloudy days.To achieve the goals,a new adaptive control system for dual-axis solar trackers with astronomical tracking was developed,which differs from traditional controls in the use of horizontal configurations under certain weather conditions.The assessment of spatio-temporal weather conditions was carried out using the Clear Sky Index(CSI)and was complemented by forecasting the panel’s power output.The study found that at 0.4 CSI values,the horizontal configuration exhibits higher power output than solar tracking systems,providing the potential to use the threshold for adaptive control.The developed system is more efficient by 18.3%,14.9%,and 10.01%than the horizontal configuration,single-axis,and dual-axis solar trackers.

Two novel approaches of adaptive finite-time sliding mode control for a class of single-input multiple-output uncertain nonlinear systems

Some systems,in spite of having multiple outputs,have only one control input,which makes their control a challenge.Two novel controllers are proposed that utilise an adaptive finite-time sliding mode control(AFSMC)scheme for a class of single-input multiple-output(SIMO)nonlinear systems in the presence of unknown mismatched uncertainties.To alleviate the inherent chattering phenomenon of sliding mode control,new forms of the two designed controllers are suggested by using new sliding surfaces.Not only can the proposed AFSMC scheme stabilise the system in a finite time,but also it can provide estimated data of the uncertainty upper bound in the controller.Lyapunov stability theory is used to obtain finite-time stability analysis of the closed-loop system.Finally,simulation results are carried out in Simulink/MATLAB for a four-dimensional autonomous hyper-chaotic system with mismatched uncertainties as an example of SIMO uncertain nonlinear systems to reveal the effectiveness of the proposed controllers.