scholarly journals Measurement-Based Distribution Grid Harmonic Impedance Models and Their Uncertainties

Energies ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 4259
Author(s):  
Ravi Shankar Singh ◽  
Vladimir Ćuk ◽  
Sjef Cobben
Keyword(s):  
Estimation Method ◽  
Distribution Grid ◽  
Harmonic Model ◽  
Equivalent Models ◽  
Grid Impedance ◽  
Before And After ◽  
Point Of Common Coupling ◽  
Simulated Network ◽  
Common Coupling ◽  
Impedance Models

Aggregated Norton’s equivalent models, with parallel impedance and current injection at different harmonic frequencies are used to model the distribution grid in harmonic studies. These models are derived based on measurements and/or prior knowledge about the grid. The measurement-based distribution (sub-)grid impedance estimation method uses harmonic phasors of 3-phase current and voltage measurements to capture the response of the distribution (sub-)grid before and after an event in the utility side of the grid. However, due to increasing non-linear components in the grid, knowledge about uncertainty in parameters of such equivalent models which intrinsically describe a linear grid becomes important. The aim of this paper is to present two novel methods to calculate the uncertainty of the measurement-based Norton’s equivalent harmonic model of the distribution (sub-)grids as seen from the utility side at the Point of Common Coupling (PCC). The impedance and the uncertainty calculations are demonstrated on a simulated network.

scholarly journals A Comparison Between Robust Control Design LMIs for Grid-Connected Converters

2021 ◽  
Author(s):  
GUSTAVO GUILHERME KOCH ◽  
CAIO RUVIARO DANTAS OSóRIO ◽  
VINICIUS FOLETTO MONTAGNER
Keyword(s):  
Superior Performance ◽  
Linear Matrix ◽  
Feedback Controllers ◽  
Quadratic Stability ◽  
Slack Variables ◽  
Grid Impedance ◽  
Point Of Common Coupling ◽  
Common Coupling ◽  
Robust Control Design ◽  
Grid Connected Converters

This paper is focused on a comparison between two linear matrix inequality conditions for design of robust state feedback controllers applied for current regulation of gridconnected converters with LCL filters, operating under uncertain grid impedance at the point of common coupling. The first condition is the well known quadratic stability and the second one is the polyquadratic stability, which uses extra matrix variables. It is shown that the condition with slack variables can provide superior performance in terms of ensuring stable and suitable operation for a larger set of uncertainties.

scholarly journals Active Power Transfer Enhancement in VSC using Impedance Compensated DSRF-PLL during Weak Grid Condition

2019 ◽  
Vol 8 (4) ◽  
pp. 2693-2966
Keyword(s):  
Active Power ◽  
Stable Operation ◽  
Phase Detection ◽  
Power Transfer ◽  
Renewable Sources ◽  
Weak Grid ◽  
Synchronous Reference Frame ◽  
Grid Impedance ◽  
Point Of Common Coupling ◽  
Common Coupling

In last two decades the use of renewable sources has been increased tremendously. This has increased the number of inverters connected to grid for the integration of energy from renewable sources. The stability of grid tied inverter is very much important with increased number of inverters. Especially in weak grid, which leads to voltage fluctuation, stability of inverter needs more attention. For a stable operation of VSC it is very important to detect the phase of grid voltage at point of common coupling (PCC) with proper accuracy. In this paper a Double Synchronous Reference Frame PLL (DSRF-PLL) with grid impedance compensation is presented. It is shown that with grid impedance compensation in phase detection, a VSC can be virtually synchronized at a stronger point of common coupling (PCC) in grid and this will enhance the active power transfer capacity of VSC with stable operation in weak grid condition. MATLAB simulation results are presented to verify the findings.

scholarly journals A Harmonic Impedance Estimation Method Based on the Cauchy Mixed Model

2020 ◽  
Vol 2020 ◽  
pp. 1-13 ◽  
Author(s):  
Zhirong Tang ◽  
Huaqiang Li ◽  
Fangwei Xu ◽  
Qin Shu ◽  
Yue Jiang
Keyword(s):  
Expectation Maximization ◽  
Mixed Model ◽  
Expectation Maximization Algorithm ◽  
Data Distribution ◽  
Estimation Method ◽  
Measured Data ◽  
Estimation Methods ◽  
Accurate Estimation ◽  
Point Of Common Coupling ◽  
Common Coupling

In this paper, a new method without any tradition assumption to estimate the utility harmonic impedance of a point of common coupling (PCC) is proposed. But, the existing estimation methods usually are built on some assumptions, such as, the background harmonic is stable and small, the harmonic impedance of the customer side is much larger than that of utility side, and the harmonic sources of both sides are independent. However these assumptions are unpractical to modern power grid, which causes very wrong estimation. The proposed method first uses a Cauchy Mixed Model (CMM) to express the Norton equivalent circuit of the PCC because we find that the CMM can right fit the statistical distribution of the measured harmonic data for any PCC, by testing and verifying massive measured harmonic data. Also, the parameters of the CMM are determined by the expectation maximization algorithm (EM), and then the utility harmonic impedance is estimated by means of the CMM’s parameters. Compared to the existing methods, the main advantages of our method are as follows: it can obtain the accurate estimation results, but it is no longer dependent of any assumption and is only related to the measured data distribution. Finally, the effectiveness of the proposed method is verified by simulation and field cases.

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.

Assessment of power quality parameters and indicators at the point of common coupling in a low voltage power grid with photovoltaic generation emulated

2022 ◽  
Vol 203 ◽  
pp. 107679
Author(s):  
Oscar Pinzón-Quintero ◽  
Daniel Gaviria-Ospina ◽  
Alejandro Parrado-Duque ◽  
Rusber Rodríguez-Velásquez ◽  
German Osma-Pinto
Keyword(s):  
Power Quality ◽  
Low Voltage ◽  
Power Grid ◽  
Quality Parameters ◽  
Photovoltaic Generation ◽  
Point Of Common Coupling ◽  
Common Coupling

Power Quality Assessment and Enhancement in a Grid Connected Renewable Energy System Using Dynamic Voltage Restorer

2014 ◽  
Vol 573 ◽  
pp. 716-721
Author(s):  
S. Rajeshbabu ◽  
B.V. Manikandan
Keyword(s):  
Neural Network ◽  
Renewable Energy ◽  
Power Quality ◽  
Energy System ◽  
Dynamic Voltage Restorer ◽  
Renewable Energy System ◽  
Voltage Restorer ◽  
Point Of Common Coupling ◽  
Dynamic Voltage ◽  
Common Coupling

Renewable energy sources provide the additional/satisfy the power to the consumer through power electronics interfaces and integrated with the grid. In grid integration power quality is one of the important parameter that need to be paying more attention. This proposed work focuses on power quality issues in a grid connected renewable energy system. Power quality issues will arises due to many factors here with the by introducing a fault condition in a grid connected renewable energy system the measurements were made at the point of common coupling and the mitigation is done with the help of a dynamic voltage restorer. The dynamic voltage restorer is a device which offers series compensation activated by neural network based controller. The sag improvement and the total harmonic assessment were made at the point of common coupling. Keywords: Neural network, Point of common coupling, Renewable energy source, Power quality, Dynamic voltage restorer ,electric grid.

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