Containment and Consensus-based Distributed Coordination Control for Voltage Bound and Reactive Power Sharing in AC Microgrid

This paper offers a highly flexible and reliable control strategy to achieve voltage bounded regulation and accurate reactive power sharing coordinately in AC Micro-Grids. A containment and consensus-based distributed coordination controller is proposed, by which each output voltage magnitude can be bounded within a reasonable range and the accurate reactive power sharing among distributed generators can be also achieved. Combined with the two proposed controllers and electrical part of the AC Micro-Grid, a small signal model is fully developed to analyze the sensitivity of different control parameters. The effectiveness of the proposed controller in case of load variation, communication failure, plug-and-play capability are verified by the experimental setup as an islanded Micro-Grid

Performance analysis of real-time PSO tuned PI controller for regulating voltage and frequency in an AC microgrid

In this study, a control strategy based on the self-tuning method and synchronous reference frame (SRF) with PI regulator is proposed to achieve optimum quality of power in an autonomous micro grid (MG). The MGS is based on multiple distributed generation (DG) connected with 120 kV power grid. The proposed system is first simulated with fixed gain values for PI controller which are not optimal for sudden changes in the system i.e. transition of MG to islanding mode, load variations. So, the particle swarm optimization (PSO) has been utilized for tuning of PI controller parameters which ensure flexible performance and superior quality of power. The principal parameters considered in this study are, regulation of voltage and frequency, steady-state and dynamic response and harmonic distortion, mainly when microgrid is islanded. The performance of PI and PI-PSO is compared in this study by simulating AC microgrid in the MATLAB/Simulink environment. Summarized results of the system are provided to authenticate viability of proposed arrangement. The proposed controller performs intelligently while regulating voltage and frequency of the MGS and utility system.

Electromagnetic Transients of a Micro-Turbine Based Distributed Generation System

Abstract-This paper evaluates the electromagnetic transients of a micro-turbine based distributed generation system that includes an AC-DC-AC converter. An outline of modelling the micro-turbine based generation system including the AC-DC-AC converter is presented. A controller for the converter, that consists of a number of single-input single-output sub-controllers, is designed based on the developed model of the system. Furthermore, the thermodynamic model of micro-turbine system is presented. The electromagnetic transients of the overall micro-turbine based generation system including the micro-turbine and converter controllers are evaluated based on time-domain simulation studies in the PSCAD/EMTDC software environment. The study considers the dynamic models of generator, converter and power system and the thermodynamic model of micro-turbine system

Frequency Control of Wind and PV Based Isolated Microgrid

The wind and solar PV based isolated microgrid can be economical and reliable for the remote area where the grid is not available. The frequency and voltage fluctuation are major problems in such remote microgrid due to intermittent nature of renewable resources like wind and solar PV. The frequency fluctuation should remain within acceptable limits for stable operation of the remote microgrid. This thesis work focuses on frequency control of wind and photovoltaic (PV) based isolated micro-grid using traditional droop control technique. The battery system acts as a master unit which is responsible for setting up the common AC bus voltage and frequency. The proportionalresonant (PR) voltage and current controllers are designed to control the current and voltage output of the voltage source inverter (VSI) connected with the DC battery. The better control performance can be obtained by using PR controller which easily tracks reference signal and eliminates steady state error in resonant frequency. The traditional droop control method is applied to generate voltage and the frequency reference set points for the VSI controller to control frequency of the AC micro-grid. The detailed analysis of the frequency control is performed by conducting two different case studies and load sharing between inverters is also presented to observe power shared by different inverters in isolated microgrid. In all the cases, system frequency is maintained within the acceptable range for the stable operation of wind and solar PV based isolated microgrid

Renewable energy system for an isolated sustainable social centre

This paper describes the development of the power converters and control algorithms to implement an isolated microgrid based in renewable energy sources used to feed a Sustainable Social Centre in a remote place. The microgrid is designed to work with photovoltaic panels, micro wind and micro-hydro turbines, or even with diesel generators. The control system of the power converters is totally digital and implemented by means of a TMS320f28335 Digital Signal Controller (DSC) from Texas Instruments. One of the most im-portant requirements imposed for the microgrid power system is the capability of providing a sinusoidal supply voltage with low harmonic distortion even in the presence of non linear electrical loads. The hardware topologies and the digital control systems of the power converters are evaluated through experimental results obtained with a developed laboratory prototype. This work is focused in the DC AC converter of the renewable energy system for the isolated Sustainable Centre.(undefined

PITOT-TUBE HEATING IN AIRCRAFTS BY SKIN EFFECT

A pitot-tube is positioned mainly to function the Airspeed Indicator (ASI), Altimeter and the vertical speed indicator (VSI). Any difference in the Pitot tube causes a great change in these flight instruments. The idea of this project is to use skin effect to become distributed within a conductor and attached to the tube overall to maintain the temperature. Skin effect as we describe, is the tendency of an alternating current (AC) to become distributed within a conductor such that current density is largest near the surface of the conductor, and decrease with greater depths within the conductor. The heat produced in the outer heat tube, can be measured and regulated with a microprocessor based, controller. This regulates the temperature reducing the risk of Pitot-tube melting and thereby avoiding pitot-tube icing at higher altitudes. The main idea is to avoid air crashes due to the misreading created due the pitot tube icing. This also lowers the power consumption, increased heating element lifespan and does not endlessly waste electricity when not in icing conditions mainly with the help of the micro controller

Smart control architecture for microgrid application

This research proposes non-linear control architectures dedicated towards improving transient response, reliability and computational burden for grid connected inverters applicable for ac micro-grids. Also this work proposes an optimization procedure applied to a small microgrid to reduce the billing cost for power incorporating battery degradation mechanism. Three works are discussed in this research that discusses methodologies to improve the operation of a three phase grid connected inverters. The first work discusses a globally stable estimation architecture for estimating the plant parameters for a grid connected inverter during its operation. Then a Lyapunov based control architecture is utilized and online parameter update scheme is used to optimize the controller performance. The second work discusses a Lyapunov based control architecture during a contingency that the grid voltage sensor fails. In this work an internal model based grid voltage estimation architecture has been proposed which successfully estimates the grid voltage and controls the grid current. The last work shows a methodology to optimally utilize a battery in a microgrid based on Markov Decision Process. Dynamic algorithm is used to solve the problem so that the cost is minimized at the end of the day. Furthermore, in this research detailed stability analysis of the first two works along with the controller design has been presented. Also in this work, battery degradation is modelled empirically and the overall cost function is obtained for the optimization of billing cost for a small microgrid. Detailed plant modeling, controller design, simulation and experimental results are presented for all of the proposed schemes --Abstract, page iv

Power management of islanded Self-Excited Induction Generator reinforced by energy storage systems

Self-Excited Induction Generators (SEIGs), e.g., Small-Scale Embedded wind generation, are increasingly used in electricity distribution networks. The operational stability of stand-alone SEIG is constrained by the local load conditions: stability can be achieved by maintaining the load’s active and reactive power at optimal values. Changes in power demand are dependent on customers’ requirements, and any deviation from the pre-calculated optimum setting will affect a machine’s operating voltage and frequency. This paper presents an investigation of the operation of the SEIG in islanding mode of operation under different load conditions, with the aid of batteries as an energy storage source. In this research a current-controlled voltage-source converter is proposed to regulate the power exchange between a direct current (DC) energy storage source and an alternating current (AC) grid, the converter’s controller is driven by any variation between machine capability and load demand. In order to prolong the system stability when the battery reaches its operation constraints, it is recommended that an ancillary generator and a dummy local load be embedded in the system. The results show the robustness and operability of the proposed system in the islanding mode of the SEIG under different load conditions

Reliability analysis of single-phase photovoltaic inverters with reactive power support

Reactive power support is expected to be an emerging ancillary requirement for single-phase photovoltaic (PV) inverters. This work assesses related reliability issues and focuses on the second stage or inversion process in PV inverters. Three PV inverter topologies are analyzed and their reliability is determined on a component-by-component level. Limiting operating points are considered for each of these topologies. The capacitor in the dc link, the MOSFETs in the inverting bridge, and the output filter are the components affected. Studies show that varying power-factor operation with a constant real power output increases the energy storage requirement as well as the capacitance required in the dc link in order to produce the double-frequency power ripple. The overall current rating of the MOSFETs and output filter must also be sized to accommodate the current for the apparent power output. Modeling of the inverter verifies the conditions for each of the components under varying reactive power support commands. It is shown that the production of reactive power can significantly increase the capacitance requirement, but the limiting reliability issue comes from the increased output current rating of the MOSFETs