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Abstract
This paper deals with “unified power quality
conditioners” (UPQCs) which aim to integrate series active and
shunt active filters. The main purpose of a UPQC is to compensate for
voltage flicker/imbalance, reactive power, negative sequence current and
harmonics. In other words, the UPQC has the capability of improving
power quality at the point of installation on power distribution systems
or industrial power systems. This paper discusses the control strategy
of the UPQC, with the focus on the flow of instantaneous active and
reactive power inside the UPQC. Some interesting experimental results
obtained from a laboratory model of 20 kVA, along with theoretical
analyses, are shown to verify the viability and effectiveness of the
UPQC
... (5), the instantaneous non-linear load power (P l ðtÞ) can be computed as. Table 7 Filter characterization with respect to voltage and current source-based non-linear load [198][199][200][207][208][209][210][211][212][213][214][215][216][217][218][219][220][221][222]. ...
... Notionally, the PRM-based controller operates by forecasting a voltage control signal for SHAF operation based on the comportment of reference and measured current and supply voltage components. This helps the output current to reach the actual reference target within the sample time [114,115,[200][201][202][203][204][205][206][207][208][209][210][211]. However, to forecast an accurate desired current, actual knowledge of the system must be required. ...
Owing to avoid harmonic and power quality issues, the concept of eliminating their impacts on microgrid systems has gained a lot of interest. Incidentally, shunt active filters (SHAFs) is selected as the most reliable solutions against the concern problems and become the first choice of researchers. However, the performance of SHAF is strictly dependent upon the controller's action, design, and stability. Looking at the necessity, the detailed working of parallel/series filters for current and voltage source-based non-linear load application is discussed and compared. This paper reviews and collects information related to various SHAF control techniques for improving microgrid performances. The effectiveness of the controller is examined and justified by considering the non-linearity reduction, dc-link voltage balancing, current and voltage regulation, and improving the synchronization techniques. In this review, the most advanced control techniques are discussed and contrasted systematically to highlight their strengths and weaknesses. In addition to that, by considering different control architectures, the possible control outcomes and shortfalls are also summarized in different tabular forms. The survey can hypothetically serve as a standard and establishment of material for selecting the most significant methods for smoothening the SHAF operation for complex microgrid systems.
... In paper [6], a new power line conditioner for harmonic compensation in power systems is presented. In paper [7], the unified power quality conditioner: the integration of series active filters and shunt active filters is presented. Steady-state operating characteristics of unified active power filters is presented in [8]. ...
The authors have already proposed using new control strategy for control operation of shunt and series active filter used separately used for suppression of current harmonic of nonlinear load for adjust THD of terminal voltage at the IEEE standard, for harmonic terminal voltage don't effect on the other loads connected on the same common coupling point on distribution power system and improving power quality. In this paper we study the validate of the unified active filter with specific control strategy, already proposed previously by the authors for operation series and shunt active filter separately, for suppression terminal voltage harmonic and current source harmonic, in case of harmonic voltage source and harmonic current source separately and simultaneously. The effectiveness and viability of the unified active filter with specific control strategy in case of harmonic voltage source and harmonic current source has been verified by theoretical analysis and simulation results. Index Terms-Active filter, power quality, harmonic suppression in distribution power system.
... Low voltage distribution systems composed of non-conventional energy systems such as wind energy systems; PV systems, small-scale hydro systems, etc. are discussed in [8,9] . These types of a distributed systems can be operated isolated or they may be interconnected to the medium voltage distribution network [10]. Its application is discussed [11] from the local side are that it provides reliability, reduces emission, also provides both thermal and electricity needs, improve power quality & reduce the cost of energy. ...
... Low voltage distribution systems composed of non-conventional energy systems such as wind energy systems; PV systems, small-scale hydro systems, etc. are discussed in [8,9] . These types of a distributed systems can be operated isolated or they may be interconnected to the medium voltage distribution network [10]. Its application is discussed [11] from the local side are that it provides reliability, reduces emission, also provides both thermal and electricity needs, improve power quality & reduce the cost of energy. ...
... The reference currents are used for generating switching pulses of shunt compensator's inverter. To improve the performance of UPQC, a novel control strategy using Fuzzy Logic Controller (FLC) is proposed which eliminates the drawback of using fixed gains in conventional PI controller [13][14][15]. In order to regulate the DC-link capacitor voltage, a conventional PI controller is used to maintain the DC-link voltage at the reference value. ...
... Despite active power filters having some demerits while performing as a separate unit, these demerits can be rectified by making both shunt and series active power filters operate simultaneously. Unified Power Quality Conditioner system is a FACTS device, which is a combination of both series and shunt active power filters coupled together by a DC link element (Fujita and Akagi 1996; Muthu Selvan 2020). ...
The utility grid is prone to power quality issues due to the advent of power
electronic devices and integration of Distributed Energy Resources. The
power quality has to be maintained despite variation in load under steady
and fault conditions. Unified Power Quality Conditioner is a FACTS device
that improves the power quality at the Distribution side of the utility grid. In
Unified Power Quality Conditioner, reactive and real power compensation is
carried out simultaneously improving the power quality. The proposed control
algorithm for Unified Power Quality Conditioner is a hybrid combination
of Reactive Power Control and Unit Vector Template. The Unified Power
Quality Conditioner is integrated with Distributed Energy Resources like
solar energy to minimize the power rating of converters and meet the
power demand. The reinforced learning algorithms have been effectively
increasing the performance of the power electronic devices; among them,
the most commonly used is the Neural-Network algorithm. The Artificial
Neural Network controller for the solar integrated Unified Power Quality
Conditioner system improves the power quality when compared to the
conventional controllers by self-adapting themselves to the environmental
needs. The system is tested under both balanced and unbalanced load
conditions with MATLAB-SIMULINK. The per-unit system has been used for
the analysis purpose to minimize the complexity. The hybrid control of the
series and shunt converters supported by solar integration at the DC link
proves to eliminate distortion caused by the non-linear load. The system is
subjected to a momentary voltage sag/swell as per IEEE 1159 standards. The
momentary sag/swell that varies between 0.5 seconds to 3 seconds has been
made to ride through less than 50 milliseconds as per the Computer and
Business Equipment Manufacture Association curve. The load side current
harmonics have been minimized inevitably by the proposed control methodology
to ensure reliability and good power factor at the Distribution side.
A comparative analysis between the conventional Proportional-Integral controller
and Artificial Neural Network controller in solar integrated Unified
Power Quality Conditioner proved the Artificial Neural Network controller
improved the harmonic reduction of various orders by an average of 12.72%.
The Total Harmonic Distortion minimization for various harmonic orders was
brought under the limits of IEEE 519 standards with Artificial Neural Network
controller.
... In addition, the APF also acts as a powerconditioning device which provides a cluster of multiple functions, such as harmonic filtering, damping, isolation and termination, load balancing, reactive-power control for power factor correction and voltage regulation, voltage flicker reduction and their combinations. Resent research presents applications of the unified power quality conditioner (UPQC) to compensate the power quality problems [4][5][6][7][8][9]. ...
Unified Power Quality Conditioner (UPQC) consists of series and shunt active filter sharing a common dc bus capacitor. The series active filter minimizes voltage source harmonics. The shunt active filter is designed to decrease harmonic current-components generated by the nonlinear loads. Thus with compensating effectively all harmonics and reactive power improve power factor. For optimal mitigation of voltage/current source harmonics, a neural network is proposed to control the UPQC. The artificial neural network (ANN) controller has been designed to extract fundamental frequency components from non-sinusoidal. Three multilayer perceptron neural networks are used to identify and reduce the harmonics. A back-propagation algorithm trains this network. Simulation carried out by Matlab/Simulink and results verify the efficiency of the proposed UPQC.
Voltage stability in integrated photovoltaic (PV) distribution systems is crucial for enabling the efficient operation of all linked equipment in the distribution network. One of the most challenging aspects of PV integration is keeping voltage profiles stable. The primary focus is maintaining a constant 22 kVA load voltage profile. In the end, we settled on a PV integrated distribution system with a single phase. Combining a differential inverter with a dynamic voltage restorer (DVR) and a distribution static synchronous compensator (D-Statcom) is a first for the power conditioning sector (UPQC). The purpose of this innovative UPQC system is to employ a fuzzy controller to successfully connect a 10 kW solar PV system to the grid. Based on these results, the optimal battery-powered UPQC control strategy may be selected. As a means of increasing PV integration and ensuring voltage stability in the distribution network, a 20 kVA UPQC was constructed. Total harmonic dispersion may be minimised by maintaining a steady distribution system frequency, voltage, and reactance/resistance ratio.
The decarbonization of the economy and the increasing integration of renewable energy sources into the generation mix are bringing new challenges, requiring novel technological solutions in the topic of smart grids, which include smart transformers and energy storage systems. Additionally, power quality is a vital concern for the future smart grids; therefore, the continuous development of power electronics solutions to overcome power quality problems is of the utmost importance. In this context, this paper proposes a novel three-phase multi-objective unified power quality conditioner (MO-UPQC), considering interfaces for solar PV panels and for energy storage in batteries. The MO-UPQC is capable of compensating power quality problems in the voltages (at the load side) and in the currents (at the power grid side), while it enables injecting power into the grid (from the PV panels or batteries) or charging the batteries (from the PV panels or from the grid). Experimental results were obtained with a three-phase four-wire laboratory prototype, demonstrating the feasibility and the large range of applications of the proposed MO-UPQC.
This paper presents a control algorithm for generation of reference voltage and current based on Observerbased QSG (Quadrature Signal Generator) for UPQC (Unified Power Quality Conditioner) in a Single-Phase Distribution System. The proposed UPQC is a combination of DSTATCOM and DVR used for load and source compensation such as voltage sag and swell, voltage and current harmonics etc. The proposed control algorithm is capable of generating reference signals from the distorted voltages and currents. In this paper, an improved OQSGbased PLL (Phase-Locked Loop) is utilized over OQSG to enable and operate with increased bandwidths that will improve the dynamic response, tracking accuracy and faster detection of reference signal under all varying load and grid conditions. The control algorithm is tested and evaluated using MATLAB / Simulink.
Emerging trends and advances in techniques in power electronics, Unified Power Quality Conditioner (UPQC) has a superior performance compared to other methods. The paper proposes the application of a ANN based UPQC to enhance the power quality of a three-phase Low-voltage network connected to a hybrid distribution generation (DG) system. The proposed work emphases the detailed performance analysis of a distributed generation system that integrates a solar PV and wind energy system by utilizing Unified Power Quality Conditioner (UPQC) with an artificial neural network (ANN) controller with respect to proportional-integral (PI) controller. The core objective of the proposed ANN is to offer good steady and dynamic state performance compared to the PID controller. The system called UPQC-ANN-RE feeds energy generated by a photovoltaic array and a wind turbine into the electrical grid and loads attached to a system of 3-phase 4-wire electrical distribution. In addition to inserting active/real power in the utility grid, the system of UPQC-ANN-RE functions as a UPQC, improving power quality signs e.g., voltage and current harmonics and power factor. A detailed analysis of the active-real power flow by converters is carried out to allow a good understanding of the operation of the UPQC-ANN-RE. The simulation outcomes are presented to assess the dynamic and steady state performance of the system of UPQC-ANN-RE connected to an electrical distribution system and to compare the consequences with the PI controller.
In this article, a unified power quality conditioner (UPQC) that does not employ line-frequency transformers (LFTs) is proposed. In the proposed UPQC, the dc links of the series H-bridge cells are fed from the dc link of the three-phase shunt cell with a unidirectional dc–dc converter isolated with a multiwinding high-frequency transformer (HFT). The three-phase shunt cell is able to compensate reactive power, current harmonics, and unbalances from the load, while the H-bridge series cells compensate voltage disturbances such as sags and swells. A control strategy of the dc-link voltages of the series cells is proposed to allow the compensation of unbalanced disturbances, and strategies to extend the operation of the converter to also compensate voltage swells are discussed. Compared with the UPQC topologies available in the literature, the proposed one does not require LFTs and does not present the operational problems of the transformerless solutions such as limitations of series compensation and balancing issues. Also, it requires fewer controlled switches than the HFT-based solutions in the literature and does not require control in the dc–dc converter. Converter model is presented as well as pulsewidth modulation, control strategy, and experimental results for validation.
Power quality disturbances have created great challenges for both electric utilities and manufacturers. Utilities must supply consumers with good quality of electric power for operating their equipment satisfactorily, and the manufactures must develop their electric equipment either to be immune to such disturbances or to override them. As a result, various techniques have been developed for the mitigation of these power quality problems. In this chapter, the various power quality issues, such as transients, harmonics, short‐ and long‐term voltage variations, and momentary power supply outages, are overviewed. Existing solutions based on passive filters and the more flexible power electronic compensation devices are reviewed with descriptions of basic circuitry and control schemes. Finally, hybrid AC/DC microgrid specific power quality issues and challenges and their compensation strategies are reviewed.
In this paper, a novel method for real-time prediction of voltage sag duration is proposed. It is based on the recently introduced new characteristic of voltage sag, named harmonic footprint, and is formulated using a logistic regression model. The concept is mathematically formulated and statistically analyzed using an extensive set of real grid measurement data which are recorded in distribution grids. Furthermore, the proposed method is applied as a part of an advanced grid-tie converter control. It is included in previously developed methods for fast sag detection and magnitude of voltage sag prediction. The algorithm is applied to the control of grid-tie converters used in distributed generators and tested with real/grid measurement data in the IEEE 13-bus test grid by simulations and in the IEEE 33-bus test grid using a hardware-in-the-loop (HIL) microgrid laboratory testbed. It is shown that this method can prevent unnecessary tripping of distributed generators (DG) and improve low-voltage ride-through (LVRT) support. In addition, the model has the potential to be applied to a wide range of devices or algorithms for the protection, monitoring, and control systems of distribution grids.
The advances in the field of power systems, distribution utilities ordinance the associated non-linear advance loads compliance with the stern power quality (PQ) enhances the reliableness of the delivery system to provide demands of censorious loads and subtle automation systems. Hurdles for sustaining quality power are linked with the continuation of elemental VAR power necessities of loads; voltage dips and swells at the point of common coupling (PCC) due to sudden switching of large industrial loads as well as VAR power indemnifying capacitors and harmonic distortions due to voltage and/or current along with non-linear loads. The harmonic distortions are pertained to be the major drawback the root cause of the PQ issues also the fluctuating pattern by loads causes degradation of voltage waveform which has been presented with variable loads. Hence, custom power device (CPD) materialized as Unified Power Quality Conditioner (UPQC) settles the issue. Intention of the work is to bring spontaneity in both the voltage and current waveform with the Sinusoidal current control strategy (SCCS), a time dominion strategy founded over instantaneous pq-theory executed with MATLAB 2016a. The results are well analyzed with proper explanation for selection of the said strategy for the UPQC. As an elementary and inherent strategy, it has titanic prospects further to be applied under photo-voltaic environment associated with a proton exchange membrane fuel cell (FC) in a hybrid grid integrated (HGI) system.
The single-phase unified power quality conditioner (UPQC) is widely used to improve the power quality of sensitive end-users. However, the inherent instantaneous power difference between parallel and series converter will generate a significant low-frequency dc-link voltage ripple and degrade the compensation performance of UPQC. The generation mechanism of dc-link voltage ripple and its influences on compensation voltage and current are analyzed in this paper. To suppress the influence, a control strategy is proposed for the single-phase UPQC. For parallel converter, a notch filter is introduced in the outer voltage loop to prevent the ripple from entering the control loop, the specific order harmonic compensation is proposed in the inner current loop to reduce the grid current harmonics. For series converter, the dc-link voltage feedback is adopted to suppress the influence of voltage ripple on the compensation performance. Simulation and experimental results show that the grid current total harmonic distortion (THD) can be reduced effectively with the fixed dc-link capacitance compared with the traditional control strategy. The load voltage THD has also been reduced by more than half by the dc-link voltage feedback control. Moreover, with the smaller dc-link capacitance, single-phase UPQC can maintain better performance under the proposed control strategy.
Unified power quality conditioner (UPQC) is now
the most relevant and optimistic mitigating equipment in modern
power systems for power quality (PQ) concerns. Optimal usage
of the dynamic voltage restorer (DVR) for load reactive powercompensation
during steady state significantly improves UPQC
utilisation, leads to improved power system efficiency and reliability.
VA loading of DVR can be regulated by maintaining an
optimal angle � between source and load voltage. This paper
introduces a novel algorithm based on variable phase angle
control (PAC) approach that incorporates evolutionary optimization
techniques to calculate this optimal angle. Population based
evolutionary optimization techniques, PSO and JAYA are used
for the same. Comparative analysis of the result is presented to
show the effectiveness of proposed algorithm. This research work
will help to develop an optimized instantaneous VA loading based
controlling strategy for UPQC for improving efficiency and the
VA loading on the UPQC.
Optimal use of DVR for load reactive power sharing
increases the utilization of overall UPQC system, efficiency and
reliability. In present paper an attempt is made to find the optimal
utilization of both PECs to minimize VA loading of overall UPQC
system using Teaching Learning based Optimization is proposed.
The simulation results demonstrate the efficacy of TLBO.
Attention has been paid to active filters for power conditioning which provide the following multifunctions: reactive power compensation; harmonic compensation; flicker/imbalance compensation; and voltage regulation. Active filters in a range of 50 kVA-60 MVA have been practically installed in Japan. In the near future, the term "active filters" will have a much wider meaning than it did in the 1970s. For instance, active filters intended for harmonic solutions are expanding their functions from harmonic compensation of nonlinear loads into harmonic isolation between utilities and consumers, and harmonic damping throughout power distribution systems. This paper presents the present status of active filters based on state-of-the-art power electronics technology, and their future prospects and directions toward the 21st Century, including the personal views and expectations of the author
This paper proposes a synchronous reference frame based controller
for a hybrid series active filter system. A hybrid series active filter
system has been designed, built and installed at Beverly Pump Station in
New England Electric utility for 765 kVA adjustable speed drive load to
meet IEEE 519 recommended harmonic standards. The series active filter
is rated 35 kVA-4% of the load kVA, and is controlled by a synchronous
reference frame based controller to act as a harmonic isolator between
the supply and load. This paper discusses the basic synchronous
reference frame controller structure and addresses its operation under
nonunity controller loop gain conditions. Design trade-offs and
implementation issues of the synchronous reference frame controller are
discussed. Operation of the hybrid series active filter system under
off-tuned passive filter conditions and its impact on the performance of
the synchronous reference frame based controller is experimentally
evaluated. Effectiveness of the series active filter to provide harmonic
damping and the use of simpler and low cost power factor correction
capacitors as passive filters, is demonstrated by laboratory
experimental results. Field installation and laboratory experimental
results demonstrate the practical viability of the synchronous reference
frame based controller for hybrid series active filter to provide
harmonic isolation of nonlinear loads and to comply with IEEE 519
recommended harmonic standards
The control of an AC power system in real time is involved because power flow is a function of the transmission line impedance, the magnitude of the sending and receiving end voltages, and the phase angle between these voltages. It has been long realized that an all solid-state or advanced, static VAR compensator, which is the true equivalent of an ideal synchronous condenser, is technically feasible and, with the use of gate turn-off (GTO) thyristors, is economically viable. This uniform approach of power transmission control promises simplified system design, reduction in equipment size and installation labor, improvements in performance, and significant reduction in capital cost that is fueled by advances in power semiconductor technology. The objective of this paper is to outline the technical and economical factors which characterize the uniform, all solid-state power-flow controller approach for real time controlled, flexible AC transmission systems. (CACT)
A technique is presented for the isolation of harmonic-sensitive loads from harmonic-producing loads, such as rectifiers and power converters. The solution, referred to as a line voltage regulator/conditioner (LVRC), utilizes a combination of a series and a parallel active power filter. The series filter isolates the sensitive loads on the output side of the LVRC from the nonlinear, distortion-producing loads on the input side by correcting for the harmonic voltage distortion present at the input. In addition, the series filter is utilized to regulate the output voltage. The parallel filter acts to generate the harmonic current required by the loads connected on the output side, therefore reflecting a linear load to the source.< >
The author outlines the technical and economic factors which
characterise the uniform, all solid-state power-flow controller approach
for real-time controlled, flexible AC transmission systems. The unified
power-flow controller in its general form can provide simultaneous,
real-time control of all basic power system parameters (transmission
voltage, impedance, and phase angle), or any combinations thereof,
determining the transmitted power. The parameters selected for control
can be changed without hardware alterations, e.g. the function of the
controller can be changed from that of a phase-shifter to that of a
series line compensator, or vice versa, with or without additional
terminal voltage regulation and shunt VAr compensation, to adapt to
particular short term contingencies or future system modifications
The conventional reactive power in single-phase or three- phase circuits has been defined on the basis of the average value concept for sinusoidal voltage and current waveforms in steady states. The instantaneous reactive power in three-phase circuits is defined on the basis of the instantaneous value concept for arbitrary voltage and current waveforms, including transient states. A new instantaneous reactive power compensator comprising switching devices is proposed which requires practically no energy storage components.
The authors present a combined system with a passive filter and a
small-rated active filter, both connected in series with each other. The
passive filter removes load produced harmonics just as a conventional
filter does. The active filter plays a role in improving the filtering
characteristics of the passive filter. This results in a great reduction
of the required rating of the active filter and in eliminating all the
limitations faced by using only the passive filter, leading to a
practical and economical system. The active filter has a much smaller
rating than a conventional active filter. Experimental results obtained
from a prototype model are shown to verify the theory developed
A novel approach to compensating for harmonics in power systems is
presented. It is a combined system of a shunt passive filter and a small
rated series active filter. The compensation principle is described, and
some filtering characteristics are discussed in detail. Excellent
practicability and validity to compensate for harmonics in power systems
are demonstrated experimentally. Although the source harmonic voltage
was only 1%, the source harmonic current reached about 10% before the
series active filter was started. After it was started, no harmonic
current flowed into the shunt passive filter. In addition, no harmonic
voltage appeared at the terminals of the shunt passive filter, because
the source harmonic voltage was applied to the series active filter. The
total loss of the series active filter was less than 40 W. It is
concluded that the combined system is far superior in efficiency to
conventional shunt active filters
Instantaneous R e active Power Compensators Comprising Switching Devices without Energy Storage Components,” IEEE h n s Akagi: “New Trends in Active Filters and Ap-p l i ~ t i o m
- H Akagi
- Y Kanazawa
- A Nabae
H. Akagi, Y. Kanazawa, and A. Nabae: “Instantaneous R e active Power Compensators Comprising Switching Devices without Energy Storage Components,” IEEE h n s . Ind. Appl., vol. 20, no. 3, pp. 625430, 1984 [l] H. Akagi: “New Trends in Active Filters,” Pmeedings of the 6th European Conference on Power Electronics and Ap-p l i ~ t i o m , Vol. 0, pp. 17-26, 1995 501
New Trends in Active Filters Pmeedings of the 6th European Conference on Power Electronics and Ap-p l i ~ t i o m
- H Akagi
H. Akagi: " New Trends in Active Filters, " Pmeedings of the 6th European Conference on Power Electronics and Ap-p l i ~ t i o m, Vol. 0, pp. 17-26, 1995
Series Active Filter for the DC Side of HVDC Transmission Systems
- E H Watanabe
E. H. Watanabe: " Series Active Filter for the DC Side of HVDC Transmission Systems, " Proceedings of the 1990 In-ternational Power Electronics Conference, Tokyo, Japan, pp. 1024-1030, 1990