Volume 14, Issue 5 -

Faults in the DC circuit constitute one of the main limitations of voltage source converter VSC-HVDC systems, as the high fault currents can damage seriously the converters. In this article, a new design for a fault current limiter (FCL) is proposed, which is capable of limiting the fault current as well as interrupting it, isolating the DC grid. The operation of the proposed FCL is analysed and verified with the most usual faults that can occur in overhead lines.

In this research study, the performance of direct torque and flux control induction motor drive (IMD) is presented using five different speed control techniques. The performance of IMD mainly depends on the design of speed controller. The PI speed controller requires precise mathematical model, continuous and appropriate gain values. Therefore, adaptive control based speed controller is desirable to achieve high-performance drive. The sliding-mode speed controller (SMSC) is developed to achieve continuous control of motor speed and torque. Furthermore, the type-1 fuzzy logic speed controller (T1FLSC), type-1 fuzzy SMSC and a new type-2 fuzzy logic speed controller are designed to obtain high performance, dynamic tracking behaviour, speed accuracy and also robustness to parameter variations. The performance of each control technique has been tested for its robustness to parameter uncertainties and load disturbances. The detailed comparison of different control schemes are carried out in a MATALB/Simulink environment at different speed operating conditions, such as, forward and reversal motoring under no-load, load and sudden change in speed.

Electric distribution feeders are inherently unbalanced and therefore have potential for severe power loss. The penetration of vehicle-to-grid (V2G) into the distribution feeders is expected to impact the power losses in the system. This is a pressing issue since power loss affects the operations, economics, and quality of service for the electric power systems. In this article, the impact of V2G parking lots on power losses of a radial distribution network is investigated. Two test networks were used in the study, namely: IEEE 13 and IEEE 123 Node test feeder networks. The test feeders and the V2G facilities were modeled in Radial Distribution Analysis Package (RDAP). Load flow results provided information on the power losses of the network. Results show that for a given penetration level, the impact of 3-phase and system-wide V2G integration on the power loss results in less power losses than 1-phase V2G integration. Results also indicate that operating the entire system such that V2G facilities will not compromise “near-balanced” state of operation and will have an improved impact on the power loss than highly unbalanced operation. The results obtained will be a useful tool for studying the impact of V2G on the power loss of a distribution network.

From the perspective of global warming suppression and depletion of energy resources, renewable energy such as wind generation (WG) and photovoltaic generation (PV) are getting attention in distribution systems. Additionally, all electrification apartment house or residence such as DC smart house have increased in recent years. However, due to fluctuating power from renewable energy sources and loads, supply–demand balancing fluctuations of power system become problematic. Therefore, “smart grid” has become very popular in the worldwide. This article presents a methodology for optimal operation of a smart grid to minimize the interconnection point power flow fluctuations. To achieve the proposed optimal operation, we use distributed controllable loads such as battery and heat pump. By minimizing the interconnection point power flow fluctuations, it is possible to reduce the maximum electric power consumption and the electric cost. This system consists of photovoltaics generator, heat pump, battery, solar collector, and load. In order to verify the effectiveness of the proposed system, MATLAB is used in simulations.

There has been a large body of statements claiming that the large-scale deployment of Distributed Energy Resources (DERs) could eventually reshape the future distribution grid operation in numerous ways. Thus, it is necessary to introduce a framework to measure to what extent the power system operation will be changed by various parameters of DERs. This article proposed a modelling framework for an overview analysis on the correlation between DERs. Furthermore, to validate the framework, the authors described the reference models of different categories of DERs with their unique characteristics, comprising distributed generation, active demand and electric vehicles. Subsequently, quantitative analysis was made on the basis of the current and envisioned DER deployment scenarios proposed for Sweden. Simulations are performed in two typical distribution network models for four seasons. The simulation results show that in general the DER deployment brings in the possibilities to reduce the power losses and voltage drops by compensating power from the local generation and optimizing the local load profiles.

Distributed Generation (DG), which is interlinked with distribution system, has inevitable effect on distribution system. Integrating DG with the utility network demands an anti-islanding scheme to protect the system. Failure to trip islanded generators can lead to problems such as threats to personnel safety, out-of-phase reclosing, and degradation of power quality. In this article, a new method for anti-islanding protection based on impedance monitoring of distribution network is carried out in presence of DG. The impedance measured between two phases is used to derive the rate of change of impedance (dz/dt), and its peak values are used for final trip decision. Test data are generated using PSCAD/EMTDC software package and the performance of the proposed method is evaluated in MatLab software. The simulation results show the effectiveness of the proposed scheme as it is capable to detect islanding condition accurately. Subsequently, it is also observed that the proposed scheme does not mal-operate during other disturbances such as short circuit and switching event.

The penetration of Vehicle-to-Grid (V2G) into the electrical distribution system has potential to create room for many operational benefits. A V2G facility installed on a distribution feeder line segment may affect power loss in the distribution system. Mathematical models are developed to study how magnitude of V2G reactive power injection and different mixes of uniformly distributed loads and lumped loads can impact power loss on a distribution system feeder. The V2G facilities assumed in this research are V2G parking lots with provision for injecting reactive currents into the feeder of a distribution network. It is shown that loss reduction can be greatly influenced by the pattern of loading, the amount of V2G reactive injection as well as position and number of V2G parking lot along the feeder segment. Useful results are obtained, with a promise that more than 95% power loss reduction (relative to power loss in the system without V2G installed) is possible by optimally locating a V2G parking lot along the feeder. It is observed that location and capacity injection of a V2G facility are the most critical for loss reduction. It was concluded that proper system planning and operational practice are required in order to reduce power losses.

This article deals with the design of an outer rotor Permanent Magnet Synchronous Machines (PMSM) driven by wind turbines. The Voltage Total Harmonic Distortion (VTHD) is especially addressed, under design parameters’ handling, i.e., the geometry of the stator, the polar arc percentage, the air gap, the skew angle in rotor poles, the pole length and the core steel class. Seventy-six cases are simulated and the results provide information useful for designing this kind of machines. The study is conducted on a 5 kW PMSM.

This article presents novel fault location algorithms for ungrounded distribution systems. The proposed methods are capable of locating faults by using obtained voltage and current measurements at the local substation. Two types of fault location algorithms, using line to neutral and line to line measurements, are presented. The network structure and parameters are assumed to be known. The network structure needs to be updated based on information obtained from utility telemetry system. With the help of bus impedance matrix, local voltage changes due to the fault can be expressed as a function of fault currents. Since the bus impedance matrix contains information about fault location, superimposed voltages at local substation can be expressed as a function of fault location, through which fault location can be solved. Simulation studies have been carried out based on a sample distribution power system. From the evaluation study, it is evinced that very accurate fault location estimates are obtained from both types of methods.

This article presents a control strategy for a three-phase grid interactive voltage source inverter that links a renewable energy source to the utility grid through a LCL-type filter. An optimized LCL-type filter has been designed and modeled so as to reduce the current harmonics in the grid, considering the conduction and switching losses at constant modulation index ( M a ). The control strategy adopted here decouples the active and reactive power loops, thus achieving desirable performance with independent control of active and reactive power injected into the grid. The startup transients can also be controlled by the implementation of this proposed control strategy: in addition to this, optimal LCL filter with lesser conduction and switching copper losses as well as core losses. A trade-off has been made between the total losses in the LCL filter and the Total Harmonic Distortion (THD%) of the grid current, and the filter inductor has been designed accordingly. In order to study the dynamic performance of the system and to confirm the analytical results, the models are simulated in the MATLAB/Simulink environment, and the results are analyzed.

This article proposed coordinated tuning and real-time implementation of power system stabilizer (PSS) with static var compensator (SVC) in multi-machine power system. The design of proposed coordinated damping controller is formulated as an optimization problem, and the controller gains are optimized instantaneously using advanced adaptive particle swarm optimization. Here, PSS with SVC installed in multi-machine system is examined. The coordinated tuning among the damping controllers is performed on the non-linear power system dynamic model. Finally, the proposed coordinated controller performance is discussed with time-domain simulations. Different loading conditions are employed on the test system to test the robustness of proposed coordinate controller, and the simulation results are compared with four different control schemes. To validate the proposed controller, the test power system is also implemented on real-time (OPAL-RT) simulator, and acceptable results are reported for its verifications.

New high-voltage (HV) substations are fed by transmission lines. The position of these lines necessitates earthing design to ensure safety compliance of the system. Conductive structures such as steel or concrete poles are widely used in HV transmission mains. The earth potential rise (EPR) generated by a fault at the substation could result in an unsafe condition. This article discusses EPR based on substation fault. The pole EPR assessment under substation fault is assessed with and without mutual impedance consideration. Split factor determination with and without the mutual impedance of the line is also discussed. Furthermore, a simplified formula to compute the pole grid current under substation fault is included. Also, it includes the introduction of the n factor which determines the number of poles that required earthing assessments under substation fault. A case study is shown.

This article presents a comprehensive statistical analysis of data obtained from a wide range of literature on the most widely used appliances in the UK residential load sector, as well as a comprehensive technology and market survey conducted by the authors. The article focuses on the individual appliances and begins by consideration of the electrical operations performed by the load. This approach allows for the loads to be categorised based on the electrical characteristics, which is particularly important for implementing load-use statistics in power system analysis. In addition to this, device ownership statistics and probability density functions of power demand are presented for the main residential loads. Although the data presented is primarily intended as a resource for the development of load profiles for power system analysis, it contains a large volume of information that provides a useful database for the wider research community.