Power Quality Of Distribution Network Research Articles

Fast network reconfiguration in harmonic polluted distribution network based on developed backward/forward sweep harmonic load flow

Power quality of distribution network is an emerging issue due to rapid increase in usage of non-linear loads on the one hand and utilization of sensitive devices on the other hand. Especially, harmonic emission is an important concern in both electric utilities and end users of electric power. Therefore, an accurate and rapid harmonic analysis method is of interest. In this paper, a non-iterative harmonic load flow (HLF) method is proposed based on backward/forward sweep technique. Proposed method is capable of performing harmonic analysis while considering linear loads and capacitor banks effects on harmonic emission in distribution network. Consideration of radial topology of distribution network in HLF, results in less computational time. Therefore, the method is more suitable for applications that needs thousands of HLFs such as network reconfiguration (NR). The proposed method is utilized in NR of capacitor compensated IEEE 69-bus distribution network while considering linear loads effects. The results confirm that the method is faster and more comprehensive than conventional HLF methods In addition, results show that the method of linear load modelling affects the reconfiguration results.

Planning of distributed generation in distribution network based on improved particle swarm optimization algorithm

Large-scale access of distributed power can improve the current environmental pressure, at the same time, increasing the complexity and uncertainty of overall distribution system. Rational planning of distributed power can effectively improve the system voltage level. To this point, the specific impact on distribution network power quality caused by the access of typical distributed power was analyzed and from the point of improving the learning factor and the inertia weight, an improved particle swarm optimization algorithm (IPSO) was proposed which could solve distributed generation planning for distribution network to improve the local and global search performance of the algorithm. Results show that the proposed method can well reduce the system network loss and improve the economic performance of system operation with distributed generation.

Impact of Photovoltaic Systems Placement, Sizing on Power Quality in Distribution Network

The paper presents a Decision Tree Algorithm for impact of photovoltaic systems placement and sizing in order to improve power quality in distribution networks. The proposed approach ...

Modeling of three-phase electric motor operation by the MATLAB system with deteriorated power quality in the 0.38 kV distribution networks

One of the main operation modes that characterizes power quality in distribution networks is asymmetry of three-phase voltage system. Operation of an induction motor (IM) with disturbed voltage symmetry in the supply network can not be considered as a rated one. The system of voltages applied to the stator winding of IM under these conditions contains positive- and negative-sequence components. This worsens the performance characteristics of IM essentially. In order to balance the 0.38 kV network operation and enhance the efficiency of the three-phase electric motor operation it is suggested to use a special balancing unit (BU) that minimizes the negative-sequence components of current and voltage. The operation modes of the obtained system “supply source – induction motor – balancing unit” are simulated within the MATLAB software package of applied programs, which allows one to assess the impact of low quality of power on the operating characteristics of the electric motor and the efficiency of the balancing unit to increase the “durability” of the motor under the asymmetrical power consumption.

Stochastics multi-objective modelling of simultaneous reconfiguration of power distribution network and allocation of DGs and capacitors

ABSTRACTThis paper suggests a method based on stochastic multi-objective modelling for optimally siting and sizing of distributed generations and capacitors and simultaneously network reconfiguration, in order to take more advantages of recent developed technologies. With respect to the widespread effect of uncertainties of load forecasting and market price, some strategies must be devised so as to well incorporate them into the problem. The mentioned problem can be regarded as a multi-objective optimisation problem for which NSGA-II accompanied by fuzzy set theory are chosen. The main aim of DisCo is to provide highly reliable power at the lowest possible costs. Besides, voltage deviation and voltage stability as the criteria of power quality in distribution networks and emission pollutant reduction are treated as independent objective functions. Eventually, to validate the effectiveness of the proposed scheme, simulations are carried out and the results are compared to the initial configuration.

Risk based multi‐objective dynamic expansion planning of sub‐transmission network in order to have eco‐reliability, environmental friendly network with higher power quality

This study suggests a method based on stochastic multi-objective modelling for optimally timing, siting and sizing of sub-transmission substationsand medium voltage feeders, distributed generations and capacitors, simultaneously, in order to take more pros of recent developed technologies. Regards to comprehensive impact of uncertainties including: intermittent nature of renewable energy sources, load forecasting and market price errors, some strategies must be devised in order to well incorporate them into the problem. The mentioned problem is modelled by dynamic programming which NSGA-2 is chosen for optimisation purposes and then fuzzy set theory is applied to find the best compromise solution. The proposed scheme aims to minimise substations expansion and installation cost, medium voltage feeders installation and replacement cost, DG units installation and operation cost, capacitors installation cost, cost of purchased energy from the transmission network, active and reactive power losses cost, and connection cost of sub-transmission substations to the upstream network. Besides, risk based modelling of energy not-supplied as an efficient reliability index is incorporated to cost function in order to improve the reliability of the network. Also voltage deviation and voltage stability as the criterion of power quality in distribution networks and emission reduction are treated as independent objective functions.

Optimal Recloser Setting, Considering Reliability and Power Quality in Distribution Networks

Reclosers and fuses are the commonplace protective devices in distribution networks. A recloser can prevent long-time outages by clearing temporary faults before operation of the fuses in the system. Thus, it decreases the rate of long-term outages and improves system reliability and power quality. Despite positive features of reclosers, each operation of a recloser causes a momentary voltage interruption that exacerbates power quality. Nowadays, power quality issues have become more important because of the increasing use of sensitive equipment to voltage interruptions. According to the mentioned concerns, it seems necessary to set reclosers to strike a balance between power quality and the effectiveness of fuse saving scheme. Thus, we proposed a method to set reclosers. Due to the random nature of faults, the proposed method is stochastic based on the Monte Carlo method. The proposed method determines the optimal number of operations, reclosing intervals, and protection zones. The proposed method efficiency is evaluated according to the simulation results, and the proposed method is capable of establishing an optimal trade-off between power quality and protection efficiency.

Why Do Electricity Policy and Competitive Markets Fail to Use Advanced PV Systems to Improve Distribution Power Quality?

The increasing pressure for network operators to meet distribution network power quality standards with increasing peak loads, renewable energy targets, and advances in automated distributed power electronics and communications is forcing policy-makers to understand new means to distribute costs and benefits within electricity markets. Discussions surrounding how distributed generation (DG) exhibits active voltage regulation and power factor/reactive power control and other power quality capabilities are complicated by uncertainties of baseline local distribution network power quality and to whom and how costs and benefits of improved electricity infrastructure will be allocated. DG providing ancillary services that dynamically respond to the network characteristics could lead to major network improvements. With proper market structures renewable energy systems could greatly improve power quality on distribution systems with nearly no additional cost to the grid operators. Renewable DG does have variability challenges, though this issue can be overcome with energy storage, forecasting, and advanced inverter functionality. This paper presents real data from a large-scale grid-connected PV array with large-scale storage and explores effective mitigation measures for PV system variability. We discuss useful inverter technical knowledge for policy-makers to mitigate ongoing inflation of electricity network tariff components by new DG interconnection requirements or electricity markets which value power quality and control.

Analysis of the Impact of Distributed Grid-Connected PV System on Power Quality of the Electrical Distribution Network

Electricity generation from solar energy by using PV cells is drastically increased due to global warming concern, greenhouse effect, and quality of living standards. However, PV generation may offer variable and unpredictable energy output due to intermittent nature of solar irradiance and hence, integration of PV into grid may provide some drawback effect to the power system. The aim of this paper is to investigate the impact of grid connected PV system on the power quality of distribution network. The power quality analysis is based on real measurements of 10 kWp, Energy Park SERT, School of Renewable Energy, Naresuan University, Thailand. Parameters such as active and reactive power, voltage, current, power factor, THDv, THDi, individual harmonic voltage and harmonic current are observed for the investigation of the interaction between SERT PV system and distribution network’s power quality. According to the measured data, PV system operation is negligible in terms of voltage distortion, voltage magnitude and frequency variation. Therefore, it can be noticed that 10 kWp SERT PV system does not effect on the distribution system power quality due to low PV penetration level.

Modified Filter for Enhancement of Power Quality in Distribution Networks

The recent rise in renewable energy sources has brought with it a corresponding rise in the utilization of Voltage Source Converters (VSCs). These typically contain a Pulse Width Modulation (PWM) switched element that can introduce harmonics into the power grid, resulting in equipment damage and failure. In order to suppress excessive harmonics and improve performance, various lowpass filters are inserted between the VSC and grid. This paper presents a comparative and systematic analysis of the LCL filter and its derivatives based on both theoretical and simulation results. The paper details the impact of each parameter on the system behaviour, as well as a performance analysis between different filter structures such as the conventional LCL filter, LLCL filter, LCL-LC filter and others. Then a design process of the modified filter is introduced with particular focus on development of a formal model which allows the filter components to be determined while maintaining filter performance and reducing damping loss.

Presented a Novel Scheme for Hysteresis Current Control by Hysteresis Current Control Grid Connected PV Three Level Inverter with LCL FilterC

Nowadays power quality is the most important issues in distributed power grids. Hysteresis current is one of the factors that reduce power quality in grid. This paper describes a hysteresis current controller inverter with application of a grid-connected PV system with application of LCL filter. The aim of this project is to reduce the hysteresis current magnitude and its THD by three levels PV gride connected inverter and remain in steady state inverter while reducing the switching frequency, reduces the losses. In addition, we add to this inverter, L filter and next time add LCL filter. We observe the function of each of them on the hysteresis current control. In fact, reducing hysteresis current causes improves power quality and final aim of this project is to improve the power quality of distribution network. This control method provides, unity power factor, load harmonic distortion reduction and reduce hysteresis current amplitude to 2.2 A. So by this method we improved power quality of distributed grid. This system uses one of the main sources of renewable energy. In this paper we want to do a complete simulation for hysteresis current control software using MATLAB / SIMULINK and SIM POWER toolbars.

Research on Harmonic Characteristics Influence for Distribution Network with Renewable Energy

In order to study the influence on harmonic characteristics of distribution network with renewable energy, a simplified model of distribution network is established to analyse theory while considering the influence of cable on the system capacitive current. Establishing an actual distribution network model by Digsilent to research the harmonic characteristics impact when photovoltaic power with PV incorporated the distribution network in a variety of different access , while using constant current source model as harmonic source model which often been used in engineering practices. The simulation results show that: optimizing the access location and dispersion of PV can decrease the waveform distortion levels in distribution network and a certain number of high-order harmonic will magnify by a specific grid structure, deteriorating the distribution network power quality.

Impact of Solar Panels on Power Quality of Distribution Networks and Transformers

This paper presents an investigation on the impact of solar panels (SPs) on the power quality of distribution networks and transformers. Both solar farms and residential rooftop SP are modeled with the distribution network according to Canadian Utility data. Total harmonic distortion of voltages and currents on both sides of the distribution transformer are monitored under different operation conditions. A laboratory setup employing a single-phase inverter and three-phase transformer is used to test system performance in the presence of phase unbalance and harmonics. Core and winding temperatures are measured under various loads. Simulation and experimentation results show that the performance of distribution networks and transformers under the impact of SPs is within standard limits.

Analysis on the Impacts of Different Distributed Generation Grid-Connected Modes on Power Quality

This paper propose the power quality evaluation index used to evaluate the impacts of the different distributed generation grid-connected modes made on power quality in the distribution network. Simulation example is built on the basis of a real distribution network as prototype using DigSilent software. Then Comparative analysis of the impacts on voltage deviation, harmonic and short duration voltage fluctuations of decentralized integration mode and centralized integration mode are made. The simulation results show that the centralized mode has more influences on the distribution network power quality, especially when there is power generated by distributed generations flowing to the main grid.

VOLTAGE SAG MITIGATION USING SUPERCAPACITOR BASED DYNAMIC VOLTAGE RESTORER

One of the major issues in improving power quality in distribution network is the mitigation of voltage sags which is caused by the system faults and adversely affects the sensitive electrical equipments involved in the end user system. End user system includes industrial production processes and large commercial customers. System faults affect sensitive equipments and result in substantial financial losses. Thus need for introduction of custom power devices emerged. One of these devices is Dynamic Voltage Restorer (DVR) which has excellent dynamic capabilities, installed between supply and a critical load feeder; it compensates voltage sags and restores line voltage to its nominal value. The proposed system comprises of a supercapacitor and the power circuit of the DVR. Thus DVR avoids any power disruption to that load. This paper presents supercapacitor based DVR using Proportional Integral (PI) controller. The system is simulated using PSCAD/EMTDC software. The graphic facility available in this software helps to carry out various aspects of model implementation and simulation results.

Fault Current Limiter: An Enabler for Increasing Safety and Power Quality of Distribution Networks

The impact of fault current limiter (FCL) devices on safety and power quality of distribution networks is quantitatively investigated. The thermal let-through caused by actual short-circuit current waveforms rather than the rms value of the symmetric component is introduced to assess the impact of the fault. Situations of vulnerability caused by a very high short-circuit current for distribution networks supplied by large power transformers, especially if operating at a lower voltage, are discussed. Concerning power quality, the possibility of restricting, by means of an FCL, the area affected by voltage dips due to a polyphase fault, thus avoiding the propagation of the disturbance to all customers, is investigated. The impact of the FCL on dispersed generation (DG) is also looked into. In particular, the possible use of FCL for avoiding unwanted trips of protection due to the DG is discussed. Finally, the possibility of interconnecting, by means of an FCL, two distribution networks without risking excessive vulnerability in the event of a fault is discussed, and the increased performance of such interconnected networks in terms of maximum permissible disturbing power is quantitatively assessed.

Performance Study of Dynamic Voltage Restorer (DVR) in Order to Power Quality Improvement

Power quality has become an increasingly important topic in the performance of many industrial applications. One of the major issues in improving power quality in distribution networks is the mitigation of voltage sags. Voltage sag can be mitigated by voltage and power injections into the distribution system using Dynamic Voltage Restorer (DVR). The DVR is a powerful controller that is commonly used for voltage sags mitigation at the point of connection. This paper describes of modeling and analysis of DVR. Different types of faults are applied for DVR in distribution network and the responses of the system for these disturbances are examined. Simulation results obtained in PSCAD/EMTDC also prove that the DVR can mitigate voltage sag and protect bus bar voltage from various types of faults.

Design of a Distribution Network Power Quality Monitoring System based on Metering Automation Systems and its Application

According to the situation that almost all the power quality systems (PQM) focus on the transmission network rather than the distribution network (DN), a distribution network power quality monitoring system (DNPQMS) based on metering automation systems is proposed in this paper. This DNPQMS can take full advantage of the power data collected by the existing intelligent terminals that set throughout the DN. The DNPQMS is divided into three parts, including equipment layer, data layer and application layer. The equipment layer consists of power quality monitoring devices, including the power quality monitoring device based on dual-CPU platform and intelligent terminals of other manufacturers. The data layer completes the power data storage and integrated that collected by the intelligent terminals. The application layer completes the day-to-day maintenance and management of the system as well as a number of advanced applications. The verification of the DNPQMS by application is presented at the end of the paper. DOI: http://dx.doi.org/10.11591/telkomnika.v10i7.1450 Full Text: PDF

Voltage regulation capability of a prototype Static VAr Compensator for wind applications

Power quality of distribution networks is severely affected with the increasing of wind penetration in power systems. One of the most important considerations in grid integration of wind energy is voltage variations. This paper presents a prototype Static VAr Compensator (SVC) that considers RMS value of grid voltage power as reference for reactive power regulation of wind turbines in order to decrease voltage fluctuations. The simulation and experimental studies have demonstrated the effective influences of the SVC on the voltage profile, even in the case of the sudden changes in the voltage magnitude. Furthermore, the experimental results give fairly good agreements with the simulation results.

A novel FACTS dynamic stabilisation scheme for stand-alone tidal energy conversion systems

Renewable abundant ocean kinetic energy has become increasingly popular as a consequence of strong ecological viable concerns and economical energy solutions in remote island communities. However, the integration of dispersed renewable tidal energy will pose a greater challenge to the power quality of distribution networks in remote areas due to fluctuation of the tidal stream velocity. The paper presents the dynamic simulation of novel stabilisation scheme with coordinated hybrid controller developed by the second author. The tidal energy converter system comprises four key parts. The tidal turbine drives an induction generator and stabilised using the novel modulated power filter MPFC and SVC compensator. The standalone renewable energy scheme feeds a hybrid electric load. The proposed integrated tidal green energy conversion scheme with all subsystems has been digitally simulated using the Matlab/Simulink/Sim-Power software environment. The novel filter compensator scheme with the dynamic error driven hybrid controller developed by the second author was fully validated.