scholarly journals Voltage Support under Grid Faults with Inherent Current Limitation for Three-Phase Droop-Controlled Inverters

Energies ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 997 ◽  
Author(s):  
Alexandros Paspatis ◽  
George Konstantopoulos
Keyword(s):  
Reactive Power ◽  
Digital Simulation ◽  
Negative Sequence ◽  
Grid Current ◽  
Voltage Drops ◽  
Fault Ride Through ◽  
Three Phase ◽  
Control Concept ◽  
Point Of Common Coupling ◽  
Voltage Support

A novel nonlinear current-limiting controller for three-phase grid-tied droop-controlled inverters that is capable of offering voltage support during balanced and unbalanced grid voltage drops is proposed in this paper. The proposed controller introduces a unified structure under both normal and abnormal grid conditions operating as a droop controller or following the recent fault-ride-through requirement to provide voltage support. In the case of unbalanced faults, the inverter can further inject or absorb the required negative sequence real and reactive power to eliminate the negative sequence voltage at the point of common coupling (PCC) whilst ensuring at all times boundedness for the grid current. To accomplish this task, a novel and easily implementable method for dividing the available current into the two sequences (positive and negative) is proposed, suitably adapting the proposed controller parameters. Furthermore, nonlinear input-to-state stability theory is used to guarantee that the total grid current remains limited below its given maximum value under both normal and abnormal grid conditions. Asymptotic stability for any equilibrium point of the closed-loop system in the bounded operating range is also analytically proven for first time using interconnected-systems stability analysis irrespective of the system parameters. The proposed control concept is verified using an OPAL-RT real-time digital simulation system for a three-phase inverter connected to the grid.

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 Simulation, Design, and Analysis of 3-Level Shunt Active Harmonic Filter using T-Typed NPC (TNPC) Topology

10.29007/s9ch ◽  
2018 ◽  
Author(s):  
Mitrajsinh Janaksinh Chudasama ◽  
Prof. Dr. P. N. Tekwani ◽  
Siddharthsingh K Chauhan ◽  
Vinod Patel
Keyword(s):  
Reactive Power ◽  
Simulation Design ◽  
Current Harmonics ◽  
Synchronous Reference Frame ◽  
Three Phase ◽  
Harmonic Filter ◽  
Non Linear ◽  
Point Of Common Coupling ◽  
Switched Mode Power Supply ◽  
Parallel Resonance

Power quality at the source side deteriorates due to current harmonics which are introduced in the power system by non-linear loads, originating a vital difficulty. Rectifiers, variable speed drive, switched mode power supply, etc. types of non-linear loads create such harmonics. Con- ventional technique to eliminate such harmonics is use of passive filters but this technique has the disadvantage of series and parallel resonance within the network impedance, overcompen- sation of reactive power at fundamental frequency and poor flexibility. Shunt Active Harmonic Filters (SAHF) are generally used to reduce current harmonics. The active harmonic filters introduce remunerating currents into the source to neutralize the harmonics possessed by the load current. The compensating currents will be derived by sensing three-phase voltages at the Point of Common Coupling (PCC) and load currents. Efforts are made in this study to ana- lyze Fast Fourier Transform (FFT) algorithm, Instantaneous Reactive Power (IRP) technique, and Synchronous Reference Frame (SRF) technique used to derive the reference compensating currents. These compensating currents act as reference currents for the fixed switching based current controllers which generate control signals for the SAHF employing three-level T-type Neutral Point Clamped (TNPC) topology of converter.

Reactive Power Limits of Single-Phase and Three-Phase DC-Link VSC STATCOMs under Negative-Sequence Voltage and Current

2021 ◽  
Author(s):  
Iosu Marzo ◽  
Jon Andoni Barrena ◽  
Alain Sanchez-Ruiz ◽  
Gonzalo Abad ◽  
Ignacio Muguruza
Keyword(s):  
Single Phase ◽  
Reactive Power ◽  
Negative Sequence ◽  
Three Phase ◽  
Power Limits

Study on a Novel Three-Phase Two-Leg Active Inverter for Electrified Railway

2015 ◽  
Vol 734 ◽  
pp. 868-872
Author(s):  
Yan Ping Sun ◽  
Mo Zhou ◽  
Guo Wang
Keyword(s):  
Simulation Model ◽  
Reactive Power ◽  
Control Method ◽  
Electric Energy ◽  
Negative Sequence ◽  
Active Elements ◽  
Three Phase ◽  
Electrified Railway ◽  
The Cost ◽  
And Control

A novel topology circuit of active compensation was discussed to be used to manage negative sequence caused by locomotive load in electrified railway. The main circuit used a three-phase two-leg compensator as active elements of shunt hybrid active compensator topology. The number of switch device in this topology was reduced by comparing with three-phase full-bridge active inverter and the cost was lower. The simulation model was developed with SIMULINK. The simulating results indicates that the shunt hybrid active compensator can restrain the problem of negative sequence which generated by locomotive load, and reduces the effect of reactive power, negative sequence, improves electric energy quality and verifies the correctness of the proposed structure and control method.

scholarly journals Compensation of Reactive Power and Unbalanced Power in Three-Phase Three-Wire Systems Connected to an Infinite Power Network

2019 ◽  
Vol 10 (1) ◽  
pp. 113 ◽  
Author(s):  
Pedro A. Blasco ◽  
Rafael Montoya-Mira ◽  
José M. Diez ◽  
Rafael Montoya ◽  
Miguel J. Reig
Keyword(s):  
Linear Systems ◽  
Reactive Power ◽  
Current System ◽  
Positive Sequence ◽  
Power Network ◽  
Negative Sequence ◽  
Three Phase ◽  
Network Losses ◽  
Infinite Power

The compensation of an electrical system from passive compensators mainly focuses on linear systems where the consumption of charges does not vary significantly over time. In three-phase three-wire systems, when the network voltages are unbalanced, negative-sequence voltages and currents appear, which can significantly increase the total apparent power supplied by the network. This also increases the network losses. This paper presents a method for calculating the compensation of the positive-sequence reactive power and unbalanced powers caused by the negative-sequence line currents using reactive elements (coils and/or capacitors). The compensation is applied to three-phase three-wire linear systems with unbalanced voltages and loads, which are connected to an infinite power network. The method is independent of the load characteristics, where only the line-to-line voltages and line currents, at the point where compensation is desired, need to be known in advance. The solution obtained is optimal, and the system observed from the network behaves as one that only consumes the active power required by a load with a fully balanced current system. To understand the proposed method and demonstrate its validity, a case study of a three-phase three-wire linear system connected to an infinite power network with unbalanced voltages and currents is conducted.

scholarly journals Reactive Power Compensation and Imbalance Suppression by Star-Connected Buck-Type D-CAP

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1914 ◽  
Author(s):  
Xiaosheng Wang ◽  
Ke Dai ◽  
Xinwen Chen ◽  
Xin Zhang ◽  
Qi Wu ◽  
...  
Keyword(s):  
Control Strategy ◽  
Reactive Power ◽  
Reactive Power Compensation ◽  
Positive Sequence ◽  
Negative Sequence ◽  
Type D ◽  
Load Imbalance ◽  
Three Phase ◽  
Unbalanced Load ◽  
Line Loss

Reactive power and negative-sequence current generated by inductive unbalanced load will not only increase line loss, but also cause the malfunction of relay protection devices triggered by a negative-sequence component in the power grid, which threatens the safe operation of the power system, so it is particularly important to compensate reactive power and suppress load imbalance. In this paper, reactive power compensation and imbalance suppression by a three-phase star-connected Buck-type dynamic capacitor (D-CAP) under an inductive unbalanced load are studied. Firstly, the relationship between power factor correction and imbalance suppression in a three-phase three-wire system is discussed, and the principle of D-CAP suppressing load imbalance is analyzed. Next, its compensation ability for negative-sequence currents is determined, which contains theoretical and actual compensation ability. Then an improved control strategy to compensate reactive power and suppress imbalance is proposed. If the load is slightly unbalanced, the D-CAP can completely compensate the reactive power and negative-sequence currents. If the load is heavily unbalanced, the D-CAP can only compensate the positive-sequence reactive power and a part of the negative-sequence currents due to the limit of compensation ability. Finally, a 33 kVar/220 V D-CAP prototype is built and experimental results verify the theoretical analysis and control strategy.

scholarly journals REACTIVE POWER ANALYSIS AT SOLAR POWER PLANT

2021 ◽  
Vol 83 (2) ◽  
pp. 47-55
Author(s):  
Aida Fazliana Abdul Kadir ◽  
Hanisah Mupangat ◽  
Dalila Mat Said ◽  
Zulhani Rasin
Keyword(s):  
Reactive Power ◽  
Solar Photovoltaic ◽  
Grid System ◽  
Pv System ◽  
Pv Inverter ◽  
Point Of Common Coupling ◽  
Grid Codes ◽  
Power Capability ◽  
Reactive Power Compensator ◽  
Voltage Support

Reactive power is essential to control the power system's voltage stability as the reactive power is directly proportional to the voltage. Hence, every new solar photovoltaic (PV) plant installed in the grid system must comply with the grid code requirements to ensure that the electricity supply remains stable and reliable. As the more penetration of PV plants, the electrical system will face some challenges related to reactive power control and voltage support. Thus, many countries including Malaysia have updated their grid codes to permit a smooth interaction between these new plants with the grid system. The inverter of PV solar connected to grid system are required to supply rated power output (MW) at point of common coupling (PCC) between the limits of 0.85 power factor lagging, and 0.95 leading follow to the Malaysian Grid Code (MGC) requirement. Hence, this research aims to design a controller for the PV inverter in Matlab/Simulink that able to absorb and supply the reactive power. Then, the comparison will execute between the simulation results and the MGC requirement. However, due to power loss in the system, the PV inverter controller may not comply with the reactive power capability as the MGC requirement. Thus, the PV system need to integrate with the capacitor bank as a reactive power compensator.

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 Mitigation of faults in grid-connected wind-driven single machine brushless double-fed induction generator

2019 ◽  
Vol 15 (3) ◽  
pp. 1178
Author(s):  
Maged Naguib Nashed ◽  
Mona Naguib Eskander ◽  
Mahmoud Saleh
Keyword(s):  
Single Machine ◽  
Reactive Power ◽  
Harmonic Distortion ◽  
Active Power ◽  
Induction Generator ◽  
Generation System ◽  
Static Synchronous Compensator ◽  
Fault Ride Through ◽  
Three Phase ◽  
Double Fed Induction Generator

<p>The effect of three-phase grid fault on the performance of a wind-driven single machine-brushless double fed induction generator (SM-BDFIG) is investigated. The fault-ride-through (FRT) of the grid-connected SM-BDFIG is then studied when installing a Static Synchronous Compensator (STATCOM) between the grid and the generator. Recovery from the grid fault before installing the STATCOM is studied and compared to the generation system recovery with installed STATCOM. The performances of the stator and rotor currents, stator and rotor voltages, electric torque, active power, reactive power, and battery pack voltage and current are presented for both cases. The total harmonic distortion (THD) of stator and rotor voltages and currents are also presented and compared. Results proved the faster recovery from grid faults, the continuity of currents and voltages, and the continuity of active power supplied to the grid when installing the STATCOM. However, slightly higher THD took place in the stator and rotor voltages and currents due to the switching pattern of the STATCOM.</p>

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