Power Quality In Distribution System Research Articles

A 3P4SW Based UPQC to Improve Power Quality in Medium Voltage Distribution System

The adverse effect of power quality issues on power distribution system due to power electronics based controllers has tremendously increased in the modern power system; therfore, it is highly desired to design a novel power quality conditioner with a minimum number of switches to compensate voltage and current distortions. This proposed configuration reduces switching losses and also effectively alleviates the performance of the power quality conditioner. This paper introduces a configuration of 3P4SW (Three Phase Four Switch) UPQC (Unified Power Quality Conditioner) for both shunt and series APF (Active Power Filter) which can be implemented in medium voltage power grid. The major challenge of phase balance with only four switches in UPQC is accomplished by adaptive Self-tuning PID using neuro-fuzzy logic control and adaptive reference current generation scheme. This controller improves sag and swells compensation with better angle control via shunt and series converter performance and passive components design. The efficacy of proposed topology is tested on MATLAB/Simulink software and results are compared with the existing three phase six switch configuration (3P6SW).

Optimal switching strategy of an SVC to improve the power quality in a distribution network

This study presents a scheme for improvement of power quality in electrical distribution systems using a static VAr compensator (SVC). The switching of the SVC has been controlled with an objective to improve the overall power quality at the distribution level. The reduction of the degree of unbalance and improvement of power factor along with minimisation of harmonics injected into the system due to the operation of SVC are identified as the objectives of the SVC switching scheme. The proposed scheme can minimise a wider range of harmonics injected into the system without any external filter. The optimised switching angles have been calculated using the particle swarm optimisation technique. An artificial neural network has been designed to predict the optimum triggering angles and the performance of the scheme for fast changing loads has been evaluated in the laboratory using a data acquisition system. Practical evaluation of power quality has been carried out at each stage of simulation and experimentation to highlight the effectiveness of the proposed scheme. The results obtained from the proposed scheme have been compared with other recent works to prove the efficacy of the system.

D-STATCOM for harmonic mitigation in low voltage distribution network with high penetration of nonlinear loads

With the increased use of power electronic for ac-to-dc converters, electrical distributions systems are experiencing an increased in non-linear loads. These non-linear loads, such as the classical rectifier, draw non-sinusoidal currents which tend to have a deleterious impact on the power quality of the modern AC distribution systems. The interaction of non-sinusoidal currents with the grid impedance leads to distorted system voltage which can adversely impact other devices connected to the grid. The integration of distributed energy resources (DERs) with the distribution power grid can further exacerbate the harmonic power issues. The traditional methods of compensation are no longer adequate and hence it is necessary to develop a means to provide local reactive and harmonic compensation at the source of the power quality problem within the low-voltage distribution network. This article investigates the use of a capacitor-less distribution static synchronous compensator (D-STATCOM) for power quality compensation in modern distribution systems. The proposed topology is based on a matrix converter (MC), controlled by finite control set model predictive control (FCS-MPC) which makes possible the use of inductive energy storage rather than electrolytic capacitors, which have been proven to be the most failure-prone components in a power electronic circuit. Simulation and experimental results are presented to validate the effectiveness of the approach.

Controller Design of UPQC for Enhancing Power Quality in Distribution System

This paper presents the procedure of PI controller design of Unified Power Quality Conditioner (UPQC) for improving power quality in the distribution system. A mathematical model of the distribution system with the UPQC is thoroughly explained in this paper. The mathematical model that is founded has been used for designing the PI controller. In order to investigate the dynamic performance and design the controller, linear approximation technique is used. Linearization of the systems that is around the operating point provides a set of linear equations, and then multi-input multi-output (MIMO) transfer functions of the systems are obtained. Two controller design techniques are presented and compared. One is the sequential loop closure controller design with parameter tuning through the Bode diagram (SLC-BD). The other one is the controller optimization design with the genetic algorithms (CO-GA). The performances of these techniques are verified and compared by using MATLAB program. Simulation results reveal that the power quality in the distribution system can be enhanced by using UPQC with the proposed controller design.

Enhancing power quality in electrical distribution systems using a smart charging architecture

The electrification of the mobility sector comes with multiple challenges such as the lack of information on when, where, how long and how fast charging processes of electric vehicles will take place. In order to keep up with increasing power demand of charging processes, besides better predictions also the active control of charging processes will be necessary to minimize infrastructure costs. This work deals with a real-time mechanism for supporting the Power Quality (PQ) in electric distribution grids in terms of congestion and voltage management. In the paper, we propose a distributed smart charging approach that considers real-time conditions of the distribution grid provided by an event-driven architecture that collects data from different points in the grid. Our approach adopts the traffic light model, which allows smooth changing of the charging power to avoid drastic changes of the grid state. In order to be ready for real-world application, the algorithm is validated by a series of experiments on two setups: Pure software (co-)simulation and Power Hardware In the Loop (PHIL) where physical charging stations and electric cars are controlled in a laboratory setup.

Performance analysis of facts devices for reduction of power quality issues in DFIG based WECS integrated to grid

Integration of a wind farm with electric grid is an issue that has gained interest due to poor power quality and unmatched power and frequency of grid. Maintenance of power quality has become an important factor in modern power systems. The usage of non-linear loads results in various power quality events which over a period would reduce life and deteriorate the performance of end user equipment. FACTS devices are available that use power electronic components provide efficient solutions for improving power quality in Distribution systems. This paper discusses performance of three FACTS devices SSSC, DSTATCOM and UPQC for mitigating voltage sags, swells and harmonics injected into a DFIG based WECS. The model is developed on MATLAB/ SIMULINK platform and results are presented.

Solar Photovoltaic System Interfaced Shunt Active Power Filter for Enhancement of Power Quality in Three-Phase Distribution System

This paper presents a solar photovoltaic (SPV) interfaced shunt active power filter (APF), which is certainly one of the utmost effective custom power devices, which mitigates the long duration current harmonics and compensates the reactive power. The shunt APF consists of the parallel connected voltage source inverter (VSI) and storage capacitor which is connected in the DC link. The compensation ability of the APF is mainly inspired by the control technique which is used to estimate the reference source current signal. Furthermore, the controller chooses the number of devices required and measurement practices; thus, it determines the corresponding costs. The fuzzy logic controller (FLC)-based second order generalized integrator (SOGI) is employed to estimate the reference source current of the shunt APF. The presented control scheme does not require voltage associated information and sensors, because it utilizes the details concerning the VSI and load currents. The shunt APF uses the solar photovoltaic (SPV) system with an auxiliary energy storage unit to deliver the required active power to the electric grid and affords the uninterrupted compensation. The performance analysis has been carried out with different load and voltage conditions through the simulation by using the MATLAB/Simulink. The experimental prototype was developed to confirm the usefulness of the PV integrated shunt APF with FLC-based SOGI control scheme.

Simulation of Reduced Rating Dynamic Voltage Restorer using SRF–ANFIS Controller

Power Quality (PQ) and reliability in distribution system have been appealing to a greater extend in modern era and also have become an area of concern for current industrial and commercial applications. This paper examines the problem of voltage sag and swells and also deals with the improved design of Dynamic Voltage Restorer (DVR) for PQ enhancement. A novel control algorithm Synchronous Reference Frame (SRF) theory with Adaptive Neuro-Fuzzy Inference System (ANFIS) controller is proposed for the creation of reference DVR voltages. In addition, different voltage injection schemes are analyzed to focus on novel method for the design of Reduced Rating DVR (RRDVR) to improve its performance in terms of output power, cost and size. The proposed DVR is demonstrated for PQ problems sag and swell using MATLAB/SIMULINK. During compensation, the output power attained from the proposed DVR is also compared with other intelligent controllers, namely Fuzzy Logic (FL) and ANFIS controller. Simulation results proved that the proposed SRF–ANFIS controller-based RRDVR offers economic solution for both utilities and customers by providing extremely deep compensation for voltage-based PQ problems occurring at very short duration of time.

Stochastic analysis of electric transportation charging impacts on power quality of distribution systems

This work studies the power quality impacts of electric transportation charging including electric buses (EBs) and electric vehicles (EVs) on distribution systems. The stochastic harmonic models for EBs and EVs and the stochastic models for their usage scenarios are built utilising the measured charging data. Based on these models, a power quality analysis method considering the charging uncertainties of EBs and EVs is proposed in this study and then their impacts on distribution systems are investigated. The Monte Carlo simulation is integrated into the proposed method to study the under voltage, overcurrent, voltage unbalance, transformer overload, harmonic current, voltage etc. caused by the stochastic charging of EBs and EVs. An actual distribution system acquired from Taiwan Power Company is taken as an example to validate the practicability of the proposed method. The test results of the proposed stochastic model are compared with those of the conservative model.

Real-Time Implementation of a Three-Phase THSeAF Based on a VSC and a P+R Controller to Improve the Power Quality of Weak Distribution Systems

This paper proposes a novel three-phase transformerless hybrid series active filter (THSeAF) based on voltage-fed type of converters (VSCs) to address major power quality issues related to residential and commercial buildings. This power quality compensator presents an affordable solution to overcome current-related issues as well as integrating renewables to ensure a sustainable supply to the loads. The controller is based on a novel combination of the synchronous reference frame and pq theory to extract voltage and current harmonics as well as voltage unbalances. A proportional resonant (P+R) regulator is producing gate switching signals for the three-phase THSeAF. The generated duty-cycle waveforms will produce compensating voltage to rectify harmonic currents initiated from typical nonlinear loads. The device ensures a reliable and dynamically restored power supply on the load's point of common coupling by means of three auxiliary dc supplies. This paper describes mitigation of power-quality-related issues of a microgrid systems and smart distribution grids along with the proposed solution to enhance the power system performances. A combination of simulations and experimental laboratory results are carried out to validate the study.

Enhancement of Power Quality in Wind Power Distribution System by using Hybrid PSO-Firefly based DSTATCOM

Electricity generation, electric power transmission and final distribution to an electricity meter are some of the processes performed in the industry of electric power. Power quality is an important factor to show the wellness of electric power. Due to the changing behavior of power generation in wind systems, more power quality issues may occur. This paper presents the simulation and analysis of Distribution Static Synchronous Compensator for voltage sag mitigation, harmonic distortion and power factor improvement using the control strategy named hybrid PSO-Firefly algorithm. The hybrid control strategy effectively enhances the performances of Distribution Static Synchronous Compensator in order to provide the faster and dynamic response. By utilizing the novel control strategy the compensation in the proposed work was completely admirable when compared with the existing techniques like proportional integral and derivative controller and proportional integral and derivative-particle swarm optimization control. The reduction of harmonics achieved to a lower percentage as 1.216 in the proposed work. The operation of simulated control method for Distribution Static Synchronous Compensator is performed in MATLAB SIMULINK.

Risk Assessment of Switchgears in Distribution System Considering Environmental Dependency

As a link between power system and users, the distribution network plays an important role. Therefore, the power quality and reliability of distribution system are of main significance to both users and power system. The switchgears are one of the most widely used components in the distribution network. Consequently, it is necessary to study the reliability of the distribution switchgears. Traditional researches on risk assessment of switchgears hardly considered the potential threat caused by high temperature, high pressure and humid environment, which is quite common in some areas especially the coastal areas of distribution network. In order to forecast the failure rates of switchgears better, the method for failure rate forecasting considering the environmental factors based on Back Propagation Neural Network (BPNN) and Support Vector Regression (SVR) are advanced in this paper. The related ambient temperature, humidity and the historical failure rate which were obtained from the actual operation distribution data from China Southern Power Grid (CSPG) are normalized firstly. And then create the training function to train the processed data. Next the BPNN and SVR are used to minimize the error between the predicted value and the actual value through iteration. A demonstration based on a coastal city in China is given to prove the validity of the algorithm. The environmental dependency result is compared with the result from the method that only the historical failure rate considered. A general conclusion can be drawn that the SVR method is more accurate than the BPNN method. And it is expected to be widely used in the whole CSPG in the future.

Multiobjective optimization for power quality monitoring allocation considering voltage sags in distribution systems

In this research, a multiobjective optimization approach is proposed to help allocate Power Quality (PQ) monitors in Distribution Systems (DS), focusing on: minimizing the cost of monitoring; minimizing topological ambiguity; maximizing the load monitoring; maximizing the amount of monitored extensions; minimizing the amount of Voltage Sags (VS) that are not monitored and maximizing the monitoring redundancy of the VS. A Multiobjective Evolutionary Algorithm with Tables (MEAT) was used to solve the problem. Results from the IEEE test systems showed that the MEAT provided the Pareto Fronts with diversified and well-distributed solutions, which made them relevant for planning monitoring systems for PQ in DS. The proposed model enables power companies to evaluate investments needed for continuous monitoring of PQ, ensuring greater flexibility in the monitoring plan and a better analysis of the cost/benefit ratio considering the six objectives presented.

Mitigation of Power Quality Problems Using Custom Power Devices: A Review

Electrical power quality (EPQ) in distribution systems is a critical issue for commercial, industrial and residential applications. The new concept of advanced power electronic based Custom Power Devices (CPDs) mainly distributed static synchronous compensator (D-STATCOM), dynamic voltage restorer (DVR) and unified power quality conditioner (UPQC) have been developed due to lacking the performance of traditional compensating devices to minimize power quality disturbances. This paper presents a comprehensive review on D-STATCOM, DVR and UPQC to solve the electrical power quality problems of the distribution networks. This is intended to present a broad overview of the various possible DSTATCOM, DVR and UPQC configurations for single-phase (two wire) and three-phase (three-wire and four-wire) networks and control strategies for the compensation of various power quality disturbances. Apart from this, comprehensive explanation, comparison, and discussion on D-STATCOM, DVR, and UPQC are presented. This paper is aimed to explore a broad prospective on the status of D-STATCOMs, DVRs, and UPQCs to researchers, engineers and the community dealing with the power quality enhancement. A classified list of some latest research publications on the topic is also appended for a quick reference.

Mitigation of Power Quality Problems Using Custom Power Devices: A Review

Electrical power quality (EPQ) in distribution systems is a critical issue for commercial, industrial and residential applications. The new concept of advanced power electronic based Custom Power Devices (CPDs) mainly distributed static synchronous compensator (D-STATCOM), dynamic voltage restorer (DVR) and unified power quality conditioner (UPQC) have been developed due to lacking the performance of traditional compensating devices to minimize power quality disturbances. This paper presents a comprehensive review on D-STATCOM, DVR and UPQC to solve the electrical power quality problems of the distribution networks. This is intended to present a broad overview of the various possible DSTATCOM, DVR and UPQC configurations for single-phase (two wire) and three-phase (three-wire and four-wire) networks and control strategies for the compensation of various power quality disturbances. Apart from this, comprehensive explanation, comparison, and discussion on D-STATCOM, DVR, and UPQC are presented. This paper is aimed to explore a broad prospective on the status of D-STATCOMs, DVRs, and UPQCs to researchers, engineers and the community dealing with the power quality enhancement. A classified list of some latest research publications on the topic is also appended for a quick reference.

Exploiting end-users capability in voltage support by means of power electronic transformer

Summary Studying reactive power has been initiated since the inception of power grids. In the past, the capacitor banks and synchronous compensators were only used to provide the reactive power. Nowadays, the game is changed, and power electronic devices have come to help with this issue. End-users inverter-based power supplies had the ability to provide real and reactive power support at the distribution level. The other device that can be used to enhance the distribution system power quality is power electronic transformer (PET) as an emerging new type of power converter. The PETs incorporated the benefits of the power electronics into conve7ntional power transformers. This paper focuses on the effects of reactive power interaction of end users and PETs in distribution level and investigates their effects on distribution level voltage profile.

Parameters Extraction of Unified Power Quality Conditioner on the Calculation of a Membership Function

The Unified Power Quality Conditioner (UPQC) has the capability of improving power quality in the industrial distribution systems. It is a combination of shunt and series active power filters, both joined together by a common Direct current (DC) bus. The major issue when utilizing the UPQC is the determination of the optimal parameters. The traditional method used to determine the optimal parameters of the UPQC is a daunting task, because the system requires greater computational and simulation efforts. This paper proposes a faster approach using the concept of a Membership Function (MF) in which a Weight Factor (WF) is utilized. In the proposed technique, a range of values is specified for each parameter of the filters. These values are used to design a membership function for each parameter, and the choice of the optimal parameter is extracted by the aid of a WF. In this study, the effectiveness of the UPQC was tested at various system conditions to verify the performance of the proposed technique. The presented results show that the obtained parameters of UPQC using the proposed technique can provide fast dynamic response.

Performance Analysis of Neural Network Training Algorithms and Support Vector Machine for Power Generation Forecast of Photovoltaic Panel

Current energy policies are encouraging the connection of power generation based on low-polluting technologies, mainly those using renewable sources to distribution networks. The photovoltaic (PV) systems have experienced a great growth around the word in last years. Hence, it becomes increasingly important to understand technical challenges, facing high penetration of PV systems at the grid, especially considering the effects of intermittence of this source on the power quality, reliability and stability of the electric distribution system. In another hand, the connections of distributed generators, by PV panels, changes voltage profile at low voltage power systems. This fact can affect the distribution networks on which they are attached causing overvoltage, undervoltage, frequency oscillations and changes in protection design. In order to predict these disturbs, because of this PV penetration, this article aims to analyze seven training algorithms used in artificial neural networks for temporal prediction of the generated active power and thus the state of the distribution network in which these microgenerators are connected and, then compare its best results with the Support Vector Machine (SVM) technique. As a result it was concluded that 3 algorithms are suitable for this type of analysis with the best performance among the seven analyzed was the Bayesian Regularization and that Artificial Neural Networks are more suitable for this problem than the SVM.

A New Structure of Dynamic Voltage Restorer Based on Asymmetrical 􀄫-source Inverters to Compensate Voltage Disturbances in Power Distribution Networks

As a consequence of sensitive, diverse and complex loads in today's distribution networks, improving power quality in distribution systems has attracted great attention. Power quality issues involve voltage sags, transient interrupts and other distortions in sinusoidal waveforms. Enormous methods have been proposed for power quality modification. One of the methods by which power quality problems might be addressed is to apply power electronic devices in the form of custom power devices. One of such devices is Dynamic Voltage Restorer (DVR) which is connected in series to distribution networks. At the same time, through injection of voltage to the network it is able to control voltage amplitude and phase. It is adopted lend to compensate for voltage sags through injecting series and synchronous three phase voltage. Consisted of three single phase inverters and a DC bus, it can protect susceptible loads against various types of voltage sags as well as other disturbances in the power supply. Moreover, it is capable of generating and absorbing active and reactive power. Therefore, in this paper, different structures of DVR have been investigated and eventually proposed a new structure for DVR based on Γ-Source asymmetric inverter. With the proposed structure, severe voltage sags can be retrieved 80- 90 percent. The simulation results that obtained by using MATLAB/Simulink indicate the properly functioning of proposed structure.

A multifunctional DSTATCOM for power quality improvement

The distribution static compensator (DSTATCOM) is used for various purposes such as load balancing, harmonic rejection, and power factor correction (PFC) in power distribution networks. In unbalanced and polluted power systems, the classic definition of power factor cannot be used for PFC due to the existence of harmonics and negative sequence components in voltage and current waveforms. In this paper, PFC is performed using the IEEE power factor definition for harmonic and unbalanced environments. Moreover, the application of a proportional-resonant (PR) controller is proposed as an effective controller in the stationary frame for DSTATCOM performance improvement. The PR controller is used in the abc-frame for load balancing and is then compared theoretically and by simulation with the conventional PI controller, which has the main drawback of steady-state error when used in the stationary frame. To improve the DSTATCOM structure, an LCL harmonic filter is used as it is advantageous over the L/LC filter in terms of the size of the filter. The proposed DSTATCOM compensates for the disturbances in the source current imposed by nonlinear, unbalanced, and low power factor loads. Simulation results show the capability of the DSTATCOM including the proposed PR controller in improving the power quality of distribution systems.