scholarly journals Determining the Responsibility of Three-Phase Unbalanced Sources Based on RICA

Energies ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2849 ◽  
Author(s):  
Yixuan Yang ◽  
Ying Wang ◽  
Xiaoyang Ma
Keyword(s):  
Least Squares Method ◽  
Coefficient Matrix ◽  
Independent Component ◽  
Negative Effects ◽  
Negative Sequence ◽  
Voltage Unbalance ◽  
Current Fluctuation ◽  
Three Phase ◽  
Point Of Common Coupling ◽  
Common Coupling

Voltage unbalance is one of the main power quality problems, and the source of many negative effects on utilities that are experienced by customers. In this paper, a method based on robust independent component analysis (RICA) for responsibility division of unbalanced sources is proposed for voltage unbalance. According to the weak correlation between negative-sequence voltage and upstream and downstream current fluctuation at the point of common coupling (PCC), the independent component of the negative-sequence voltage and current fluctuation at the point of common coupling is obtained by RICA. The blind source mixing coefficient matrix can be obtained according to the least squares method. The equivalent negative-sequence impedance on both sides of the PCC can be obtained using the linear correlation between the mixing coefficients. Finally, according to the principle of partial pressure, the unbalance contribution of the upstream and downstream at the PCC is calculated. The method is accurate for upstream and downstream impedance estimation compared with the traditional method, and has a strong anti-interference ability. When the background noise or system fluctuation is large, the responsibility division result is still accurate. The correctness and effectiveness of the proposed method are proven by the simulation of the experimental circuit.

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 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 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>

Determining Harmonic Contributions Based on Reweighted Complex Least Squares Method

2013 ◽  
Vol 448-453 ◽  
pp. 2660-2666
Author(s):  
Hui Chun Hua ◽  
Xiu Fang Jia ◽  
Hai Qing An ◽  
Shao Guang Zhang
Keyword(s):  
Quality Management ◽  
Least Squares ◽  
Power Quality ◽  
Least Squares Method ◽  
Test System ◽  
Important Task ◽  
Reasonable Result ◽  
Point Of Common Coupling ◽  
Common Coupling

Determining harmonic contribution quantitatively at the point of common coupling is an important task for power quality management. Outliers and influential points could have strong influences on regressors. This paper puts forward a method named reweighted complex least squares to eliminate or reduce the influences to ensure the robustness of the regression. The method can improve precision of the equivalent harmonic impedance and it can get a more reasonable result in harmonic contribution determination than previous methods. A case study based on the IEEE 14-bus test system was conducted, which shows the validity of the proposed method.

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.

scholarly journals Unbalanced Voltages Impacts on the Energy Performance of Induction Motors

2018 ◽  
Vol 8 (3) ◽  
pp. 1412 ◽  
Author(s):  
Enrique C. Quispe ◽  
Iván D. López ◽  
Fernando J. T. E. Ferreira ◽  
Vladimir Sousa
Keyword(s):  
Induction Motor ◽  
Induction Motors ◽  
Energy Performance ◽  
Positive Sequence ◽  
Negative Sequence ◽  
Voltage Unbalance ◽  
Three Phase ◽  
Motor Load ◽  
Sequence Parameters

<p class="Abstract">This paper presents the results of a study about the effects of unbalanced voltages on the energy performance of three-phase induction motors. The principal contribution of this paper is that presents a detailed analysis of the influence of positive and negative sequence voltage components and the angle between them on several characteristics such as: line currents, losses, efficiency and power factor under different voltage unbalanced conditions. A three-phase induction motor of 3 HP was used as a case study. The results of the investigation show that the positive sequence voltage must be considered together with the voltage unbalance factor (VUF) or percent voltage unbalance (PVU) index to evaluate the performance of the induction motor. It is also shown that the behavior of the motor load influences on the positive sequence parameters next to the voltage, while in the case of negative sequence only influences the negative sequence voltage.</p>

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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