Moayed Moghbel

A new adaptive configuration of PID type fuzzy logic controller

In this paper, an adaptive configuration for PID type fuzzy logic controller (FLC) is proposed to improve the performances of both conventional PID (C-PID) controller and conventional PID type FLC (C-PID-FLC). The proposed configuration is called adaptive because its output scaling factors (SFs) are dynamically tuned while the controller is functioning. The initial values of SFs are calculated based on its well-tuned counterpart while the proceeding values are generated using a proposed stochastic hybrid bacterial foraging particle swarm optimization (h-BF-PSO) algorithm. The performance of the proposed configuration is evaluated through extensive simulations for different operating conditions (changes in reference, load disturbance and noise signals). The results reveal that the proposed scheme performs significantly better over the C-PID controller and the C-PID-FLC in terms of several performance indices (integral absolute error (IAE), integral-of-time-multiplied absolute error (ITAE) and integral-of-time-multiplied squared error (ITSE)), overshoot and settling time for plants with and without dead time.

Coordinated charging of PEVs in unbalanced residential network based on worst node voltage profile

Plug in Electric Vehicles (PEVs) have recently become available and are starting to penetrate the distribution system as new loads. There are a few potential issues associated with uncoordinated (random) charging of PEVs such as network congestion and overloading of distribution transformers. This paper explores the detrimental impacts of random PEV charging on the distribution transformer loading and bus voltage profiles of an unbalanced smart grid. The impacts of deferred plugging of vehicles that could be encouraged by introducing higher electricity prices during the peak load hours are also explored. Finally, a practical coordinated PEV charging approach through controlling the worst node voltage profile is proposed and implemented. Simulation results are presented using Matlab/Simulink software.

Effects of iron-core topology on inrush currents in three-phase multi-leg power transformers

This paper investigates the inrush currents of three-phase (a)symmetric multi-leg transformer cores considering magnetic core structure (e.g., three-leg vs. five-leg) and switching effects (e.g., recloser operating). The electromagnetic steady-state and transient behavior of three-phase transformers significantly differs from single-phase transformer operation mainly because of the unique flux coupling interactions in multi-leg and asymmetric core structures. A recently developed three-leg nonlinear transformer core model is applied to this study which considers the influence of magnetic hysteresis, flux couplings in the core-structure and nonsinusoidal operation in three-phase transformers. Simulations results for multi-leg (e.g., three-leg and five-leg) transformer cores demonstrating inrush current behavior based on the model are presented and discussed.

Power system transient stability enhancement using direct drive wind generators

Recent grid codes requires the wind farms not only to ride through the fault disturbances but also support the stability of nearby grid during severe network disturbances. This paper presents the impact of direct drive wind generators to the improvement of fault ride through (FRT) capability of fixed speed wind turbine. Three operational strategies have been investigated, i.e. without reactive power support, considering reactive power support complying with the Danish grid codes (with and without considering overloading of the converter currents). The proposed control strategies enable the direct drive wind generators to inject the required reactive power in order to help stabilizing the nearby fixed speed wind generators during faults. Simulation studies are carried out by using MATLAB/SIMULINK.

Optimal Sizing, Siting and Operation of Custom Power Devices with STATCOM and APLC Functions for Real-Time Reactive Power and Network Voltage Quality Control of Smart Grid

A new custom power device (CPD) is introduced for real-time control of reactive power and improving the overall network voltage quality of smart grid (SG) at fundamental and harmonic frequencies, respectively. The idea is to take advantage of the online smart meter data transmitted from each bus to the SG central control to concurrently perform the static synchronous compensator and the active power line conditioner operations by optimal compensations of fundamental reactive power and harmonic currents at selected optimal buses. The proposed strategy involves two particle swarm optimization algorithms. The first algorithm is implemented for the worse operating condition to determine the optimal locations and sizes of CPDs while the second algorithm relies on smart meter information to continuously compute fundamental and harmonic reference currents for real-time operation and control of the allocated CPDs. The objective functions are cost minimizations associated with bus voltage regulations, network total harmonic distortions voltage and custom device sizing while the constraints include upper limits for CPD sizes, fundamental, and harmonic bus voltages. Detailed simulations are performed in MATLAB/Simulink to evaluate the performances of allocated CPDs in controlling the reactive power and voltage quality of a distorted 15-bus SG with six nonlinear loads according to the IEEE-519 standard.

D-STATCOM based on hysteresis current control to improve voltage profile of distribution systems with PV solar power

The increasing penetration of renewable power generations such as PV power plants in distribution systems is creating serious voltage quality problems such as voltage fluctuations, voltage imbalance and voltage instability. These issues can be solved by injecting reactive power to the grid. Reactive power control of transmission lines through the static synchronous compensator (STATCOM) has gained wide attentions due to its phenomenal performance. This paper investigates the voltage instability problems in distribution systems integrated with rooftop photovoltaic (PV) resources and presents a solution based on the incorporation of distribution STATCOM (D-STATCOM). It will present modeling, simulation and hysteresis current control (HCC) of D-STATCOM to improve power quality problems including line short circuit, voltage sag and voltage swell. Simulation results are performed and analyzed in Matlab/Simulink to investigate the performance and ability of D-STATCOM under various operating conditions.

Optimal placement and sizing of multiple STATCOM in distribution system to improve voltage profile

Power quality is an important issue when integrating renewable distributed generations and power electronic devices in distribution systems. Possible issues are unacceptable voltage fluctuation and harmonic current injections that may result in unstable and unreliable power networks. Voltage profile can be improved by compensating reactive power using flexible AC transmission systems (FACTSs) such as the static synchronous compensator (STATCOM) which has gained wide attention due to its prodigious performance. The main objectives of this paper are placement and sizing of STATCOM units as well as evaluating their performances using particle swarm optimization (PSO) to improve voltage profiles of highly distorted distribution systems. The 15-bus unbalanced test system is used for the analyses and simulations. A five level neutral-point clamped (FL-NPC) inverter with an adaptive hysteresis current controller (AHCC) is used to model the STATCOM in Matlab/Simulink.

Derating active power filters considering network and bus voltage total harmonic distortions

The most practiced and acceptable approach to improve the power quality of distorted distribution networks is to install active power filters (APFs) at the point of common couplings (PCCs) of nonlinear loads. This approach has proven to be very effective since APFs fully compensate for the injected current harmonics at the PCCs that will effectively result in negligible voltage total harmonic distortion (THDv) of the entire network. The main drawback of APFs is that they are relatively expensive and not feasible for small facilities. This paper proposes a simple and practical approach for reducing the cost of APFs by derating them under the worst operating condition. The idea is instead of designing APFs to completely eliminate the injected current harmonics at their PCCs, reduce their ratings such that the overall network THDv is within permissible limit recommended by the power quality standards. Simulation results are presented and compared for the distorted IEEE 31 bus 23kV network without and with APFs considering different levels of filter deratings.

Power Quality Improvement Using an Enhanced Network-Side-Shunt-Connected Dynamic Voltage Restorer

Abstract Among the four basic dynamic voltage restorer (DVR) topologies, the network-side shunt-connected DVR (NSSC-DVR) has a relatively poor performance and is investigated in this paper. A new configuration is proposed and implemented for NSSC-DVR to enhance its performance in compensating (un)symmetrical deep and long voltage sags and mitigate voltage harmonics. The enhanced NSSC-DVR model includes a three-phase half-bridge semi-controlled network-side-shunt-connected rectifier and a three-phase full-bridge series-connected inverter implemented with a back-to-back configuration through a bidirectional buck-boost converter. The network-side-shunt-connected rectifier is employed to inject/draw the required energy by NSSC-DVR to restore the load voltage to its pre-fault value under sag/swell conditions. The buck-boost converter is responsible for maintaining the DC-link voltage of the series-connected inverter at its designated value in order to improve the NSSC-DVR capability in compensating deep and long voltage sags/swells. The full-bridge series-connected inverter permits to compensate unbalance voltage sags containing zero-sequence component. The harmonic compensation of the load voltage is achieved by extracting harmonics from the distorted network voltage using an artificial neural network (ANN) method called adaptive linear neuron (Adaline) strategy. Detailed simulations are performed by SIMULINK/MATLAB software for six case studies to verify the highly robustness of the proposed NSSC-DVR model under various conditions.

Improving the Learning Experience of Power System Protection Students using Computer-based Simulations and Practical Experiments

This paper presents a survey on the activities carried out to improve the learning experience of electrical engineering undergraduate students in power system protection unit in Cur-tin University, Australia. The unit was conducted initially based on lectures and tutorials where only two sessions on computer simulation and one session of laboratory demonstration were conducted. In academic year of 2013, to improve the learning experience of students, several computer-based simulations and laboratory experiments were prepared. The students are introduced with two power system analysis software, namely ETAP and PSCAD/EMTDC which are used to demonstrate the over-current relays performance and their coordination as well as the time transient analysis of different faults in an electric network where some protection relays are applied. A practical setup composed of LabVolt electrical modules and SEL relays is used to simulate an electric network. Several tests are built up to simulate fault and protection layout for transformer and induction motor. Finally, a secondary injection test set is used to introduce the concepts of relay testing and commissioning.