scholarly journals Admittance Reshaping Control Methods to Mitigate the Interactions between Inverters and Grid

Energies ◽  
2019 ◽  
Vol 12 (13) ◽  
pp. 2457 ◽  
Author(s):  
Ling Yang ◽  
Yandong Chen ◽  
An Luo ◽  
Kunshan Huai
Keyword(s):  
Design Method ◽  
Harmonic Distortion ◽  
Response Speed ◽  
Control Methods ◽  
Dynamics Model ◽  
Specific Design ◽  
Three Phase ◽  
Point Of Common Coupling ◽  
Common Coupling ◽  
System Phase

With the increasing impedance coupling between inverters and grid caused by the phase-locked loop (PLL), traditional three-phase inverters suffer from the harmonic distortion or instability problems under weak grid conditions. Therefore, the admittance reshaping control methods are proposed to mitigate the interactions between inverters and grid. Firstly, a dynamics model of traditional inverter output admittance including main circuit and PLL is developed in the direct-quadrature (dq) frame. And the qq channel impedance of the inverter presents as a negative incremental resistance with the PLL effect. Secondly, two admittance reshaping control methods are proposed to improve the system damping. The first reshaping technique uses the feedforward point of common coupling (PCC) voltage to modify the inverter output admittance. The second reshaping technique adopts the active damping controller to reconstruct the PLL equivalent admittance. The proposed control methods not only increase the system phase margin, but also ensure the system dynamic response speed. And the total harmonic distortion of steady-state grid-connected current is reduced to less than 2%. Furthermore, a specific design method of control parameters is depicted. Finally, experimental results are provided to prove the validity of the proposed control methods.

scholarly journals A Proposed Harmonic Monitoring System for Large Power Users Considering Harmonic Limits

Energies ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 4507
Author(s):  
Rosalia Sinvula ◽  
Khaled Mohamed Abo-Al-Ez ◽  
Mohamed Tariq Kahn
Keyword(s):  
Monitoring System ◽  
Renewable Energy Sources ◽  
Electronic Devices ◽  
Harmonic Distortion ◽  
Large Power ◽  
High Penetration ◽  
Point Of Common Coupling ◽  
Common Coupling ◽  
Power Utilities ◽  
The Individual

Most power utilities within Southern Africa are faced with the challenges of harmonic distortion due to the high penetration of renewable energy sources (RES) and the use of electronic devices. There is an excessive total harmonic distortion (THD) measured at the point of common coupling (PCC). In this paper, a proposed harmonic monitoring system for large power users (LPUs) is developed. This proposed system considers harmonic limits of the individual and THD of the customers allowed injecting into the network, which should be part of the contractual electricity supply agreement (ESA). Hence, it will enable the monitoring of harmonic distortion to be smooth by determining whether the customer has passed or failed compliance for individual harmonic order and the THD of the voltage. The measurements of harmonic distortion are done using the Unipower power quality (PQ) analyzers that are connected at different points within the industrial network. Measurements of harmonic distortion of an industrial site are compared to the simulation results performed by DIgSILENT software to validate the proposed harmonic monitoring system. Based on the validation results, it is recommended that the ESA between the power utilities and the customers should consist of the harmonic limits.

scholarly journals Design of a Proportional Resonant Controller with Resonant Harmonic Compensator and Fault Ride Trough Strategies for a Grid-Connected Photovoltaic System

Electronics ◽  
2018 ◽  
Vol 7 (12) ◽  
pp. 451 ◽  
Author(s):  
Saif Islam ◽  
Kamran Zeb ◽  
Waqar Din ◽  
Imran Khan ◽  
Muhammad Ishfaq ◽  
...  
Keyword(s):  
Fault Location ◽  
Photovoltaic System ◽  
Pv System ◽  
Simulink Model ◽  
Fault Ride Through ◽  
Three Phase ◽  
Point Of Common Coupling ◽  
Switch Type ◽  
Resonant Controller ◽  
Common Coupling

This paper presents the design and analysis of a proportional resonant controller with a resonant harmonic compensator and switch-type fault current limiter, as a fault-ride through strategy for a three-phase, grid-connected photovoltaic (PV) system under normal conditions and asymmetrical faults. The switch-type fault limiter comprised of current-limiting inductors, a bridge rectifier, a snubber capacitor, linear transformers, and energy absorption bypass. Furthermore, a critical and analytical comparison of switch-type fault limiters is carried out, with the conventional crowbar as the fault-ride through strategy, in combination with a conventionally tuned proportional integrator controller. The designed fault-ride through strategies with proportional integrator and proportional resonant controllers with resonant harmonic compensators are tested at the point of common coupling of the photovoltaic system and at a distance of 19 km from the point of common coupling, in order to analyze the impacts of fault parameter with respect to location. A MATLAB/Simulink model of a 100 kW three-phase grid-connected photovoltaic system is used for analysis. The simulation results of the proposed switch-type fault limiter with proportional resonant controller effectively validate the stable, ripple-free, and robust response compared to all other configurations. In addition, it is also verified that the grid faults on the PV system have a significant impact on fault type, and less impact on fault location.

scholarly journals Generation of Optimal Switching Angle for Nine Level Cascaded H Bridge MLI Using Most Valuable Player Algorithm

2021 ◽  
Vol 12 (6) ◽  
pp. 1919-1927
Author(s):  
Vijaya Anand N, Hema Latha J, G Devadasu, Kumar C
Keyword(s):  
Reactive Power ◽  
Harmonic Distortion ◽  
Voltage Level ◽  
Computing Technique ◽  
Power Exchange ◽  
Point Of Common Coupling ◽  
Terminal Voltage ◽  
Common Coupling ◽  
Micro Grids

Distributed generation (DG) sources often interfaced with grid by a Cascaded H-bridge multilevel inverter with a remote D.C source. The interface inverter has to adapt voltage on the either side of the grid and DG source while it has a control of active and reactive power exchange. The inverter terminal voltage is maintained based on frequency switching technique. However, in applications like micro grids are based on quality of output voltage at the point of common coupling. The present paper discusses an optimal frequency switching methodology that generates optimal fringing angle based on an evolutionary computing technique while maintaining the voltage level at PCC with a reduced harmonic distortion.  Efficacy of the proposed method is illustrated by simulating a 9-level cascaded H bridge in MATLAB environment.

scholarly journals Simulation on microgrid connected PV system under balance and unbalance fault

2019 ◽  
Vol 13 (3) ◽  
pp. 1332
Author(s):  
Ameerul A. J. Jeman ◽  
Naeem M. S. Hannoon ◽  
Nabil Hidayat ◽  
Mohamed M. H. Adam ◽  
Ismail Musirin ◽  
...  
Keyword(s):  
Photovoltaic System ◽  
Pv System ◽  
Matlab Simulink ◽  
Three Phase ◽  
Point Of Common Coupling ◽  
Simulation Results ◽  
Common Coupling ◽  
Types Of Faults ◽  
Three Phases

<p><span>This paper presents an analysis in Matlab/Simulink of a three-phase photovoltaic system under balance and unbalance faults in Matlab/Simulink. The aim of this paper is to investigate the performance of the system under various types of fault. The simulation involved various types of faults occurring at different distances from the point of common coupling of the PV system. This paper also aimed to identify what type of fault that may severely damage the system. The simulation results presented in this paper show that the three-phase fault in the microgrid was severely affecting the system since it involved all the three phases of the system while the distance of the fault occurrence is less influenced in the system. The purpose of this research is to observe the effect on the system based on the types of faults occur and the distance faults occur.</span></p>

A New Compensation Control Strategy for Grid-connected Wind Turbine and Fuel Cell Inverters in a Microgrid

2017 ◽  
Vol 8 (1) ◽  
pp. 272 ◽  
Author(s):  
A. Naderipour ◽  
A. A. Mohd Zin ◽  
M. H. Habibuddin ◽  
M. Moradi ◽  
M. Miveh ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Wind Turbine ◽  
Distributed Generation ◽  
Control Method ◽  
Harmonic Distortion ◽  
Synchronous Reference Frame ◽  
Wide Range ◽  
Point Of Common Coupling ◽  
Frame Method ◽  
Common Coupling

The use of a new control method for grid-connected inverters for reducing the output current harmonic distortion in a wide range of grid-connected distributed generation (DG) applications, including wind turbine (WT) and fuel cell (FC) inverters is proposed in this paper. The control method designed to eliminate main harmonics in a microgrid (MG) and between MG and point of common coupling (PCC) and responsible for the correction of the system unbalance. Another advantage of the proposed control method is that it can be easily adopted into the DG control system without the installation of extra hardware. The proposed control method is comprised of the synchronous reference frame method (SRF). Results from the proposed control method are provided to show the feasibility of the proposed approach.

scholarly journals Voltage Compensation Using Dvr with Modified Switching Band Control

2018 ◽  
Vol 7 (4.24) ◽  
pp. 53
Author(s):  
Sura.Srinivasa Rao ◽  
Choppavarapu.Sai Babu
Keyword(s):  
Switching Frequency ◽  
Simulation Studies ◽  
Dynamic Voltage Restorer ◽  
Switching Losses ◽  
Voltage Restorer ◽  
Three Phase ◽  
Voltage Compensation ◽  
Point Of Common Coupling ◽  
Dynamic Voltage ◽  
Common Coupling

This paper presents mitigation of voltage related Power Quality (PQ) issues by using Dynamic Voltage Restorer (DVR). Three phase four wire DVR with modified switching band controller is proposed. A modified filter circuit band controller is proposed for reducing the switching losses, constant switching frequency maintenance and corresponding simulation studies are carried out. Variable hysteresis band (modified band) controller generates accurate injected voltages by using system parameters and low error value between reference injected voltages, actual injected voltages can be achieved, which helps in smoothening and minimizing ripples in PCC (Point of common coupling) voltages. The obtained simulation results are presented.

Evaluation of Superimposed Sequence Components of Currents based Islanding Detection Scheme during DG Interconnections

2016 ◽  
Vol 17 (1) ◽  
pp. 1-14 ◽  
Author(s):  
Karan Sareen ◽  
Bhavesh R. Bhalja ◽  
Rudra Prakash Maheshwari
Keyword(s):  
Operating Conditions ◽  
Cycle Duration ◽  
Islanding Detection ◽  
Detection Scheme ◽  
Distributed Generations ◽  
Three Phase ◽  
Sequence Components ◽  
Point Of Common Coupling ◽  
Common Coupling ◽  
Nuisance Tripping

Abstract A new islanding detection scheme for distribution network containing different types of distributed generations (DGs) is presented in this paper. The proposed scheme is based on acquiring three phase current samples for full cycle duration of each simulation case of islanding/non-islanding conditions at the point of common coupling (PCC) of the targeted DG. Afterwards, superimposed positive & negative sequence components of current are calculated and continuously compared with pre-determined threshold values. Performance of the proposed scheme has been evaluated on diversified islanding and non-islanding events which were generated by modeling standard IEEE 34-bus system using PSCAD/EMTDC software package. The proposed scheme is capable to detect islanding condition rapidly even for perfect power balance situation for both synchronous and inverter based DGs. Furthermore, it remains stable during non-islanding events such as tripping of multiple DGs and different DG interconnection operating conditions. Therefore, the proposed scheme avoids nuisance tripping during diversified non-islanding events. At the end, comparison of the proposed scheme with the existing scheme clearly indicates its advantage over the existing scheme.

Research on Seamless Transfer Strategy of Micro-Grid Based on Energy Storage

2013 ◽  
Vol 805-806 ◽  
pp. 1129-1135
Author(s):  
Qi Zhang ◽  
Zai Jun Wu ◽  
Xiao Bo Dou ◽  
Chun Jun Sun ◽  
Bo Zhao
Keyword(s):  
Energy Storage ◽  
Vital Role ◽  
Control Mode ◽  
Three Phase ◽  
Point Of Common Coupling ◽  
Micro Grid ◽  
Common Coupling ◽  
Voltage Control Mode ◽  
Seamless Transfer ◽  
And Control

Energy storage plays a vital role in the reliable operation of Micro-Grid (MG) due to its characteristic of running stabilization and control flexibility. It can act as the master inverter and maintain system voltage and frequency stability as MG in off-grid mode under voltage control mode. During the transfer of MG from grid-connected mode to off-grid mode, the PCC (point of common coupling) three-phase static switch cant shut off at the same time. Moreover it needs to match the MG voltage and utility grid voltage when the islanded MG needs to reconnect to the utility grid.In order to solve these problems, a control strategy of grid-connected/off-grid seamless transfer based on energy storage is proposed. Simulation was presented from a MG platform including photovoltaic (PV), wind turbine (WT) and energy storage and the result shows the feasibility of the proposed approach.

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