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The ever mounting demand of electrical energy and the keen scarcity of conventional energy sources leads to the burgeon of distributed generation (DG) system. The main abstruse is the harmonization of the DG to the utility grid. Generally current regulated PWM voltage-source inverters (VSI) are used for synchronizing the utility grid with DG source in order to meet the following objectives: 1) To...
A reliable islanding detection method is one of the most important function of a well designed inverter based distributed generation (DG) system. Active islanding detection methods have negligible non-detection zone, but they bring some power quality issues to the network. In this paper an islanding detection method which addresses constant current inverter based DGs is introduced. It has both high...
This paper deals with the power flow analysis and control strategy research of unified power quality conditioner (UPQC). A UPQC is a combination of shunt and series active power filter (APF), sharing a common dc link. It can compensate almost all power quality problems such as voltage harmonics, voltage unbalance, voltage flickers, voltage sags, voltage swells, current harmonics, current unbalance,...
Voltage source converter based DSTATCOM has been accepted as the most preferred solution for reactive power management in distribution power networks which plays a vital role in improving power quality, correcting power factor and maintaining constant distribution voltages. However, the quality of DSTATCOM output voltage and current itself, such as injected harmonics and Total Harmonic Distortion...
The unified power quality conditioner (UPQC) is a combination of back to back connected shunt and series active power filters (APFs) to a common DC link voltage, which compensates voltage and current based distortions, independently. Generally the power conditioning devices are designed for complete compensation, irrespective of the requirement/priority. In this paper flexibility of selective compensation...
Due to a large amount of non-linear power electronic equipments, impact and fluctuating loads (such as that of arc furnace, heavy merchant mill and electric locomotive, etc), problems of power quality have become more and more serious with each passing day, as a result Active power filter (APF) gains much more attention due to excellent harmonic compensation. But still the performance of the active...
In most of the situations, power electronics converters are mainly used as an interfacing device between distributed generation (DG) system and utility grid in order to meet the following objectives: 1) grid synchronization 2) active and reactive power control through voltage and frequency control 3) improvement of power quality (i.e. harmonic elimination) etc. But due to wide variation of the reactive...
In this paper, a dual-loop control scheme is proposed for inverters in three-phase four-wire microgrid applications to improve the power quality within the microgrid and the power quality of the current flowing between the microgrid and the utility grid. The control scheme involves an inner voltage loop and an outer current loop, with both controllers designed using the H∞ repetitive strategy. This...
This paper presents a new control strategy for adaptive hysteresis current control based power quality studies for an induction motor to eliminate harmonics and to compensate the reactive power. The adaptive hysteresis band current controller changes the hysteresis bandwidth according to modulation frequency, supply voltage, dc capacitor voltage and slope of the reference compensator current wave...
This paper presents a single phase grid-connected PV system integrating energy storage system (ESS) using cascaded multilevel inverter. A Discrete Fourier Transform (DFT) Phase Locked Loop (PLL) method is proposed to improve system dynamic performance. A coordinated active and reactive power management (ARPM) strategy is developed based on the dual-stage DFT PLL method. The point of common coupling...
Growing numbers of consumers distort AC networks with harmonics. Therefore suppression of the network pollution should be considered. This problem can be solved by using "network-friendly" converters. In this article some consumers are presented that pollute the single-phase AC networks with harmonics. Therefore the network voltage waveform will be distorted. In our study we examine the...
This paper presents a Zeta DC-DC converter as a power factor correction (PFC) converter which is operated in voltage control mode for speed control of a permanent magnet brushless DC motor (PMBLDCM). The proposed converter performs the PFC action and DC link voltage control in single stage and needs only one controller. The current multiplier approach with average current control is employed for PFC...
In this paper, a neural network based reference current computation method for active power filter (APF) control under non-ideal mains voltage with different load condition is proposed. The neural network controller has been designed to extract fundamental frequency components from non-sinusoidal and unbalanced currents. These fundamental frequency components will be used as unit templates. The APF...
STATCOM has been widely proposed for power quality and network stability improvement. It is easily connected in parallel to the electric network and has many advantages for electrical grids. It can improve network stability; power factor, power transfer rating and can avoid some disturbances such as sags and swells. Most of STATCOM controllers are based on voltage controllers that are based on balance...
Smart grids offer a wide application domain for power electronics. In fact, every distributed energy resource (DER) includes an electronic power processor (Switching Power Interface, SPI) which controls the currents drawn from the grid and can be driven to optimize the power flow, improve voltage stability and increase distribution efficiency. For these aims, such distributed SPIs must perform cooperatively...
Multilevel converters can reach medium-voltage operation, increasing the efficiency in high power applications. Among the existing multilevel converter topologies, modular multilevel converter provides the advantages of high modularity, availability and high power quality. Moreover, the main advantage compared to cascaded multilevel converters is the absence of input transformer; reducing the size,...
To connect distributed generation units to a low-voltage four-wire distribution network, a suitable three-phase converter topology needs to be chosen. To improve the power quality in the grid, the distributed generation unit can be used as an active power filter (APF). When an active power filtering function is desired, the converter should have a neutral wire to allow neutral currents to flow. Therefore,...
This paper presents a single-phase Z-source inverter as a power conditioning system for a grid-connected system. Z-source inverter is a single-stage topology that has buck-boost feature, which is possible because of additional shoot through state introduced in zero state of the conventional inverter pulse width modulation and provides desired output AC voltage. Small DG system with alternate energy...
Battery Energy Storage System (BESS) is used for load compensation of a permanent generator synchronous generator driven by diesel engine to enhance its performance. The control of BESS with capabilities of reactive power, harmonics and unbalanced load compensation is achieved by indirect current control scheme. The modeling of the DG set is performed using permanent magnet synchronous generator (PMSG)...
Traditionally, unified power quality conditioners (UPQCs) are designed for simultaneous compensation of voltage and current harmonics and imbalances. Moreover, the shunt active filter of the UPQC behaves as a controlled current source to compensate the load current, whereas the series active filter behaves as a controlled voltage source to compensate the supply voltage. Here, a dual configuration...
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