GA-Based Reliability Enhancement in Distribution Systems Through Sagged Bus Numbers Reduction by Optimal Placement of Unified Series-Shunt Compensator

This paper presents a new method to reliability improvement of distribution system by optimal sizing and placement of unified series -shunt compensator (USSC).The GA based approach is used to solve the USSC optimization problem with considering capital cost of USSC installation and interruption costs due to interruption of loads in sensitive point. In this paper using ETAP software, the worst point that if three phase fault occur, therefore leads to the propagation of voltage sags to most number of system buses is investigated and located. Simulation results show that the proposed method is efficient and feasible for improving the system reliability level by reducing the number of sagged bus and load outages and momentary interruptions. Finally in this paper, after optimal location of USSC, the reliability improvement is investigated through expected energy not supplied (EENS) index, average system interruption frequency index (ASIFI) and the momentary average interruption frequency index (MAIFI)

Simulation study of FACTS devices based on AC-AC modular multilevel hexagonal chopper

This paper proposes a new range of FACTS device based on direct AC-AC conversion, where the modular multilevel AC hexagonal chopper (M2AHC) is employed. The M2AHC is operated in quasitwo-level (Q2L) mode; and the heterodyne modulation is used to decouple voltage amplitude regulation from the phase shift; thus, independent control of active and reactive power is achieved. Then, a family of FACTS devices based on M2AHC that offers voltage, active power and reactive power flow control as both shunt and series compensators is analyzed. The use of AC cell capacitors instead of DC capacitors in M2AHC makes its footprint much smaller and lighter than conventional AC-DC or DC-AC voltage source converter (VSC) based FACTS devices; hence, high reliability and extended service life could be expected. The system modeling and controller design of the proposed FACTS devices are illustrated in a unified reference frame, considering different control modes, transient and unbalanced conditions. Simulation results are used to verify the feasibility of the proposed M2AHC based FACTS device. These FACTS devices will be preferred over conventional counterpart for confined spaced applications such as the grid access of large-scale offshore wind farms and resolution of loop flow in megacities

Online Control of Modular Active Power Line Conditioner to Improve Performance of Smart Grid

This thesis is explored the detrimental effects of nonlinear loads in distribution systems and investigated the performances of shunt FACTS devices to overcome these problems with the following main contribution: APLC is an advanced shunt active filter which can mitigate the fundamental voltage harmonic of entire network and limit the THDv and individual harmonic distortion of the entire network below 5% and 3%, respectively, as recommended by most standards such as the IEEE-519

Modelling of power electronics controllers for harmonic analysis in power systems

The research work presented in this thesis is concerned with the modelling of this new generation of power electronics controllers with a view to conduct comprehensive power systems harmonic analyses. An issue of paramount importance in this research is the representation of the self-commutated valves used by the controllers addressed in this work. Such a representation is based on switching functions that enable the realization of flexible and comprehensive harmonic models. Modularity is another key issue of great importance in this research, and the model of the voltage source converter is used as the basic building block with which to assemble harmonic models of actual power systems controllers. In this research the complex Fourier series in the form of operational matrices was used to derive the harmonic models. Also, a novel methodology is presented in this thesis for conducting transient analysis of electric networks containing non-linearities and power electronic components. The methodology is termed the extended harmonic domain. This method is based on the use of time-dependent Fourier series, operational matrices, state-space representation and averaging methods. With this method, state-space equations for linear circuit, non-linear circuits, and power electronics controllers models are obtained. The state variables are the harmonic coefficients of x(t) instead of x(t) itself. The solution of the state-space equations gives the dynamic response of the harmonic coefficients of x(t). Moreover, a new harmonic power flow methodology, based on the instantaneous power flow balance concept, the harmonic domain, and Newton-Raphson method, is developed and explained in the thesis. This method is based on the instantaneous power balance as opposed to the active and reactive power balance, followed by traditional harmonic power flow methods. The power system and the power electronics controllers are modelled entirely in the harmonic domain

Dynamic Harmonic Domain Modeling of Flexible Alternating Current Transmission System Controllers

Flexible alternating current transmission system (FACTS) and multi-line FACTS controllers play an important role in electrical power transmission systems by improving power quality and increasing power transmission capacity. These controllers are nonlinear and highly complex when compared to mechanical switches. Consequently, during transient conditions, it is very difficult to use conventional time and frequency domain techniques alone to determine the precise dynamic behavior of the harmonics introduced into the system by these controllers. In particular, the time-varying nature of the harmonic components is not captured by these techniques. The contribution of this work to the state of power systems analysis is the development of new models for seven important and widely-used FACTS controllers (static synchronous series compensator (SSSC), unified power flow controller (UPFC), fixed capacitor-thyristor controlled reactor (FC-TCR), thyristor controlled switched capacitor (TCSC), generalized unified power flow controller (GUPFC), interline power flow controller (IPFC), and generalized interline power flow controller (GIPFC)) using a technique called the dynamic harmonic domain method. These models are more accurate than existing models and aid the power systems engineer in designing improved control systems. The models were simulated in the presence of disturbances to show the evolution in time of the harmonic coefficients and power quality indices. The results of these simulations show the dynamic harmonic response of these FACTS controllers under transient conditions in much more detail than can be obtained from time-domain simulations, and they can also be used to analyze system performance under steady-state conditions. Some of the FACTS controllers\u27 models discussed in this work have a common DC link, but for proper operation, the DC side voltage must be held constant. The dynamic harmonic domain method was applied to the FACTS devices to design feedback controllers, which help in maintaining constant DC

Dynamic Harmonic Domain Modeling of Flexible Alternating Current Transmission System Controllers

Flexible alternating current transmission system (FACTS) and multi-line FACTS controllers play an important role in electrical power transmission systems by improving power quality and increasing power transmission capacity. These controllers are nonlinear and highly complex when compared to mechanical switches. Consequently, during transient conditions, it is very difficult to use conventional time and frequency domain techniques alone to determine the precise dynamic behavior of the harmonics introduced into the system by these controllers. In particular, the time-varying nature of the harmonic components is not captured by these techniques. The contribution of this work to the state of power systems analysis is the development of new models for seven important and widely-used FACTS controllers (static synchronous series compensator (SSSC), unified power flow controller (UPFC), fixed capacitor-thyristor controlled reactor (FC-TCR), thyristor controlled switched capacitor (TCSC), generalized unified power flow controller (GUPFC), interline power flow controller (IPFC), and generalized interline power flow controller (GIPFC)) using a technique called the dynamic harmonic domain method. These models are more accurate than existing models and aid the power systems engineer in designing improved control systems. The models were simulated in the presence of disturbances to show the evolution in time of the harmonic coefficients and power quality indices. The results of these simulations show the dynamic harmonic response of these FACTS controllers under transient conditions in much more detail than can be obtained from time-domain simulations, and they can also be used to analyze system performance under steady-state conditions. Some of the FACTS controllers\u27 models discussed in this work have a common DC link, but for proper operation, the DC side voltage must be held constant. The dynamic harmonic domain method was applied to the FACTS devices to design feedback controllers, which help in maintaining constant DC

DFT-based recursive group-harmonic energy distribution approach for power interharmonic identification

AbstractThe Discrete Fourier Transform (DFT) is still a widely used tool for analyzing and measuring both stationary and transient signals in power system harmonics. However, the misapplications of DFT can lead to incorrect results caused by some problems such as the aliasing effect, spectral leakage and picket-fence effect. The strategy of a DFT-based recursive Group-harmonic Energy Distribution (GED) algorithm is developed for system-wide harmonic/interharmonic evaluation in power systems. The proposed algorithm can restore individual dispersing spectral leakage energy caused by the DFT, and thus retrieve respective real harmonic/interharmonic value. Every distribution of energy minimizing iteration procedure for harmonic/interharmonic evaluation can be convergent fast, and therefore guarantee each harmonic/interharmonic magnitude and respective frequency approaches its actual value. Consequently, not only can high precision in integer harmonic measurement be retained, but also the interharmonics can be identified accurately, particularly under system frequency drift. A numerical example is presented to verify the proposed algorithm in terms of robust, fast and precise performance

Power quality and electromagnetic compatibility: special report, session 2

The scope of Session 2 (S2) has been defined as follows by the Session Advisory Group and the Technical Committee: Power Quality (PQ), with the more general concept of electromagnetic compatibility (EMC) and with some related safety problems in electricity distribution systems. Special focus is put on voltage continuity (supply reliability, problem of outages) and voltage quality (voltage level, flicker, unbalance, harmonics). This session will also look at electromagnetic compatibility (mains frequency to 150 kHz), electromagnetic interferences and electric and magnetic fields issues. Also addressed in this session are electrical safety and immunity concerns (lightning issues, step, touch and transferred voltages). The aim of this special report is to present a synthesis of the present concerns in PQ&EMC, based on all selected papers of session 2 and related papers from other sessions, (152 papers in total). The report is divided in the following 4 blocks: Block 1: Electric and Magnetic Fields, EMC, Earthing systems Block 2: Harmonics Block 3: Voltage Variation Block 4: Power Quality Monitoring Two Round Tables will be organised: - Power quality and EMC in the Future Grid (CIGRE/CIRED WG C4.24, RT 13) - Reliability Benchmarking - why we should do it? What should be done in future? (RT 15

Optimization of FACTS devices : classification, recent trends, and future outlook

Since the inception of industrialization, power system has been an indispensable aspect of economy. With the progression of time, technology has impalpably commingled into our lifestyle. Alongside blooming technologies, energy demand is proliferating and power companies are begetting energy at their best to quench it. Growing reliance on power system has brought its quality into more advertence. Various electronic devices and topologies have been invented to enhance power quality and reliability; numerous others are still underway. During the course, power system has grown to an intricate network of sources, loads and control devices, leading to various issues such as transmission congestion and high losses. This paper discusses ways to ameliorate congestion and gives an overview of relationship between our present energy resources and ecological threats like global warming. Moreover, it points out various power system problems such as energy losses and transients. The necessity of FACTS devices has also been elaborated alongside their classification and comparison. Finally, numerous topologies and optimization methods proposed in the technical literature have been classified and analyzed to alleviate power system conundrums, and a glimpse into future energy trends is presented

Grid Voltage Synchronization for Unbalanced Voltages Using the Energy Operator

This paper presents a novel synchronization technique which can identify the grid voltage frequency and phase angle under unbalanced grid voltage conditions. The method combines the features of two different energy operator schemes: the basic one for estimating the frequency of the grid voltages and the cross-energy operator for phase tracking. Using a moving data window of five samples the algorithm can track the fundamental frequency and phase angle quickly and accurately. The paper discusses the fundamental principles of the method, highlights its features and filter requirements in implementation. An experimental implementation of this method is presented which validates its performance for practical operation. The ability of the proposed method to enable a STATCOM riding-through unbalanced grid voltage condition is verified by the results from a power network simulation study