Showing papers in "Electric Power Components and Systems in 2012"
TL;DR: An expert system based on an artificial neural network for fault classification and distance estimation is proposed in this article and is proven to be successful for classification and location of the faults.
Abstract: The ability to locate the faults as well as to identify the type of fault in overhead transmission lines is of prime importance for the economic operation of modern power systems. An expert system based on an artificial neural network for fault classification and distance estimation is proposed in this article. The power system network has been simulated using EMTP/ATP software, and signal analysis has been performed in MATLAB environment (The MathWorks, Natick, Massachusetts, USA). Various types of faults have been simulated at different locations along the transmission line. The faulty voltage signals have been analyzed through wavelet transform using the Db4 mother wavelet. The entropies of the wavelet decompositions have been fed to the neural networks for classification and fault distance evaluation. The suggested technique is proven to be successful for classification and location of the faults.
80 citations
TL;DR: In this paper, a new approach for the genetic algorithm is applied to solve the optimal power flow problem based on different objective functions and the main distinction of this technique is in using the adapted genetic algorithm with adjusting population size.
Abstract: In this article, a new approach for the genetic algorithm is applied to solve the optimal power flow problem based on different objective functions. The main distinction of this technique is in using the adapted genetic algorithm with adjusting population size. The objective functions are minimized using various controlled system variables (generator voltages, transformer taps, and shunt capacitors). The feasibility of the proposed method is presented on the IEEE 30-bus system and compared to other well-established techniques. A comparison with other methods shows the effectiveness of the proposed technique.
75 citations
TL;DR: In this article, an efficient and reliable optimization procedure based on the behaviors of swarm in nature, namely the gravitational search algorithm, is proposed for solving multi-objective optimal reactive power dispatch problems, which minimizes transmission loss while maintaining the quality of voltages.
Abstract: In this article, an efficient and reliable optimization procedure based on the behaviors of swarm in nature, namely the gravitational search algorithm, is proposed for solving multi-objective optimal reactive power dispatch problems, which minimizes transmission loss while maintaining the quality of voltages. The gravitational search algorithm is based on Newton's law of gravity and interaction of masses. In the proposed algorithm, the searcher agents which are a collection of masses interact with each other using Newton's laws of gravity and motion. In order to investigate the performance of the proposed scheme, multi-objective optimal reactive power dispatch problems are solved. This new gravitational search algorithm method is tested on IEEE 57-bus and IEEE 118-bus power systems. Results obtained by the gravitational search algorithm are compared with two versions of genetic algorithms, three versions of differential evolution algorithms, four versions of particle swarm optimization algorithms...
75 citations
TL;DR: In this paper, a new circuit topology of a high-voltage step-up boost DC-DC converter for photovoltaic power systems is presented, which has various advantages compared to the conventional boost converters, namely, a higher boost rate with low duty cycle, lower voltage stress on components, and higher efficiency.
Abstract: This article presents a new circuit topology of a high-voltage step-up boost DC-DC converter for photovoltaic power systems. The converter boosts the low-output voltage of the solar cell to the required voltage for the load. The proposed circuit has various advantages compared to the conventional boost converters, namely a higher boost rate with low duty cycle, lower voltage stress on components, and higher efficiency. The equations of a dual-boost converter are analyzed, highlighting the advantages of the new DC/DC converter circuit topology. The operation principle is explained using the operating intervals equivalent circuits and operation waveforms. Then, mathematical and theoretical analyses of continuous and discontinuous conduction modes of the converter are presented. Losses and thus efficiency of the proposed converter are calculated using MATLAB (The MathWorks, Natick, Massachusetts, USA). Calculations are used to compare the efficiency of the proposed topology with others available in ...
58 citations
TL;DR: In this article, a simulation and experimental study of a sliding-mode controller of the DC bus voltage of a three-phase shunt active power filter is presented to improve tracking performance characteristics, power quality, and minimized consumption of reactive power.
Abstract: This article presents a simulation and experimental study of a sliding-mode controller of the DC bus voltage of a three-phase shunt active power filter. The sliding-mode controller is introduced to improve tracking performance characteristics, power quality, and minimized consumption of the reactive power. The algorithm used to identify the reference currents is based on the self-tuning filter. The firing pulses of the insulated-gate bipolar transistor inverter are generated using a hysteresis current controller, which is implemented on an analog card. Finally, this study, under steady-state and transient conditions, is illustrated with signal-flow graphs and corresponding analysis. This study was verified by both time-domain computer simulations and experimental tests on a hardware prototype based on dSPACE-1104 (dSPACE, Germany). The experimental results show the feasibility and the effectiveness of the designed active filter associated with a sliding-mode controller and its capability in meeti...
57 citations
TL;DR: A novel methodology that employs a goal programming technique and genetic algorithm for formulation and evaluation of a multi-objective function, respectively, for optimal planning of distributed generator units in the distribution system is proposed.
Abstract: This article proposes a novel methodology that employs a goal programming technique and genetic algorithm for formulation and evaluation of a multi-objective function, respectively, for optimal planning of distributed generator units in the distribution system. The multi-objective function consists of various performance indices that govern the optimal operation of a distribution system with distributed generator units. The proposed method aims to greatly diminish the dependence in existing methods on the global preference information of the distribution system planner by means of simplicity in problem formulation utilizing a goal programming technique. The capacity of the distribution system to accept distributed generator integration is evaluated such that with the placement of every additional distributed generator unit, the value of multi-objective function reduces without any violation in the system operating constraints. The effectiveness of the proposed method is tested using various distr...
56 citations
TL;DR: A three-phase multilevel inverter topology is reported that generates voltage levels similar to the corresponding well-known conventional diode-clamped, flying capacitors and cascaded H-bridge inverters but with fewer power circuit components and simplicity.
Abstract: This article reports a three-phase multilevel inverter topology. The multilevel inverter configuration generates voltage levels similar to the corresponding well-known conventional diode-clamped, flying capacitors and cascaded H-bridge inverters but with fewer power circuit components and simplicity. By optimizing the proposed switching patterns through analysis, the total harmonic distortion of the inverter output line voltage waveforms have been reduced. The validity of the proposed cascaded multilevel inverter is verified through simulation and experiments.
42 citations
TL;DR: In this article, the design of optimal automatic generation control regulators for an interconnected power system operating in a deregulated environment is presented, where an extra-highvoltage AC transmission line in parallel with a high-voltage DC link is considered as an area interconnection between the two areas.
Abstract: This article presents the design of optimal automatic generation control regulators for an interconnected power system operating in a deregulated environment. An extra-high-voltage AC transmission line in parallel with a high-voltage DC link is considered as an area interconnection between the two areas. The dynamic model of the power system under consideration is developed by incorporating various types of possible market transaction environments. The designed optimal automatic generation control regulators are implemented, and dynamic system responses for various system states are obtained considering load perturbation in one of the areas. The patterns of open-loop and closed-loop eigenvalues are also determined to ensure system stability with and without optimal automatic generation control regulators. From the investigations carried out in the work, it is inferred that the dynamics performance of the system under consideration has an appreciable improvement when a high-voltage DC link is inco...
36 citations
TL;DR: In this article, a combination method based on S-transform and the hidden Markov model is presented for power quality disturbance classification, which computes the maximum likelihood probability between training and testing data signals for identification.
Abstract: In this article, a combination method based on S-transform and the hidden Markov model is presented for power quality disturbance classification. S-transform is a new method that has been used in signal processing and power quality disturbance classification applications. S-transform not only has the advantages of both wavelet transform and fast Fourier transform but also characteristics superior than both mentioned transform methods. Besides, the hidden Markov model is a powerful and effective method on signal processing applications. This method computes the maximum likelihood probability between training and testing data signals for identification. The proposed method makes the classification more simple and accurate. The identification procedure has two major steps. First, features are extracted by S-transform, and in the second step, classification is done using a decision tree structure of hidden Markov models. Simulation results by simulated and experimental test signals reveal the robustn...
35 citations
TL;DR: In this paper, the adaptive neuro fuzzy inference system was used for high-impedance fault analysis (detection, classification, and location) in distribution networks using a new approach.
Abstract: This article presents a new approach for high-impedance fault analysis (detection, classification, and location) in distribution networks using the adaptive neuro fuzzy inference system. The proposed scheme was trained by data from simulation of a distribution system under various faults conditions and tested for different system conditions. Details of the design process and the results of performance using the proposed method are discussed in this article. The results show that the proposed technique has very good performance in detecting, classifying, and locating high-impedance faults. The third harmonics, magnitude, and angle for the three-phase currents give superior results for fault detection as well as for fault location in high-impedance faults. The fundamental components magnitude and angle for the three-phase currents give superior results for the classification phase of high-impedance faults over other types of data inputs.
35 citations
TL;DR: In this paper, a digital signal processor based three-phase four-wire shunt active power filter is analyzed to compensate nonlinear and unbalanced loads under non-ideal supply voltages conditions.
Abstract: Shunt active power filters are the most viable solution for solving current harmonic, reactive power compensation, and load unbalancing problems widely presented in electrical distribution systems. In this article, development and implementation of a digital signal processor based three-phase four-wire shunt active power filter are analyzed to compensate non-linear and unbalanced loads under non-ideal supply voltages conditions. The proposed algorithm is divided into two parts, the first associated with the calculation of the positive-sequence component of unbalanced supply voltage and second deriving a simple and attractive fundamental extraction filter to extract the fundamental frequency component from distorted positive-sequence voltage. Average power and DC-link energy balance methods are used to calculate peak value of the supply current, which is required to flow from source to load. The behavior and effectiveness of the proposed control algorithm has been verified by simulation using MATL...
TL;DR: In this article, the sub-optimal automatic generation control regulator designs of a two-area interconnected power system using output feedback control strategy are presented, where the proposed regulators are designed using a modified area control error, which incorporates the DC tie-line power deviation in the modeling of area control errors.
Abstract: This article presents the sub-optimal automatic generation control regulator designs of a two-area interconnected power system using output feedback control strategy. The power system consists of identical plants with reheat thermal turbines and is interconnected via parallel AC/DC links. Efforts have been made to propose sub-optimal automatic generation control regulators based on the feedback of output state variables, which may easily be accessible and available for measurement. In addition, the proposed regulators are designed using a modified area control error, which incorporates the DC tie-line power deviation in the modeling of area control errors. The system dynamic performance has been investigated with the implementation of designed sub-optimal automatic generation control regulators in the wake of 1% load disturbance in one of the two areas. Also, system dynamic responses with optimal automatic generation control regulators for the same power system model are obtained to compare the s...
TL;DR: The results show that the proposed intelligent controller improved the dynamic response of the system faster than the conventional controller and provided a control system that satisfied the load frequency control requirements.
Abstract: One of the main observed problems in the control of automatic generation control systems is the limitation to access and measurement of state variables in the real world. In order to solve this problem, an optimal output feedback method, the linear-quadratic regulator controller, is used. In the output feedback method, only measurable state variables within each control area are required to use for feedback. But in order to improve dynamic performance and provide a better design for this controller, the concept of an intelligent regulator is added to the linear-quadratic regulators; as a result, the particle swarm optimization based linear-quadratic output feedback regulator and the imperialist competitive algorithm based linear-quadratic output feedback are proposed to calculate the global optimal gain matrix of con- troller intelligently. The optimal control law of this controller must be determined by minimizing a performance index under the output feedback conditions leading to coupled matrix equations. In conventionalmethods, the control law is handled by pole placement, iterative, or trial-and-error methods for choosing controller gains; thus, intelligent optimization techniques are applied to solve this problem. The proposed controllers are tested on a two-area automatic generation control power system, and a complete comparison between the proposed output feedback controllers with adaptive weighted particle swarm optimization, particle swarm optimization, the imperialist competitive algorithm, and a conventionaloutput feedbackcontroller is presented.The results show that the proposed intelligent controller improved the dynamic response of the system faster than the conventional controller and provided a control system that satisfied the load frequency control requirements.
TL;DR: In this article, an advanced non-linear control algorithm is proposed to manage active power and voltage provided by a synchronous generator based on the feedback linearization theory, which relies on the central concept to algebraically transform nonlinear systems dynamics into fully or part linear ones, so that linear control techniques can be applied.
Abstract: This article proposes an advanced non-linear control algorithm to manage active power and voltage provided by a synchronous generator. The algorithm is based on the so-called feedback linearization theory, which relies on the central concept to algebraically transform non-linear systems dynamics into fully or partly linear ones, so that linear control techniques can be applied. Starting from the basic (electrical, magnetic, and mechanical) machine equations, a suitable state transformation is introduced in order to apply the feedback linearization block to the generator model. A regulation scheme is then derived, which receives as inputs the measure and reference signals of both the electric power and the voltage at the generator side and produces as outputs the physical inputs of the machine, i.e., the mechanical torque and the field voltage. Particular attention is devoted to both the linearization process, where internal dynamics and stability studies play an important role, and to the design ...
TL;DR: In this article, general analytical equations were developed for the calculation of electromagnetic fields due to an inclined channel directly in the time domain, where the input parameters, angle of inclination of the lightning channel and the angle at the observation point can be varied through all possible values to produce the relevant electromagnetic fields.
Abstract: This article describes general analytical equations that are developed for the calculation of electromagnetic fields due to an inclined channel directly in the time domain. The input parameters of the model, angle of inclination of the lightning channel and the angle at the observation point can be varied through all possible values to produce the relevant electromagnetic fields. The proposed model is validated with eight electromagnetic waveforms measured at close range of the lightning channel. The results of the model show good agreement with the measured data. Furthermore, the proposed equations are compatible with different channel base current functions. The equations could easily be applied in the coupling models that calculate induced voltages in conductors in the presence of lightning-generated electromagnetic fields.
TL;DR: In this article, a new full-scheme distance protection for a series-compensated transmission line is proposed, where a combination of hyperbolic S-transform and learning machines is applied for fault detection, classification, and location, which are three main aspects of distance relays.
Abstract: In this article, a new full-scheme distance protection for a series-compensated transmission line is proposed. The new combination of hyperbolic S-transform and learning machines is applied for fault detection, classification, and location, which are the three main aspects of distance relays. The hyperbolic S-transform is used for extracting useful features from the current and voltage signals sample of the power system from one terminal. The extracted features are employed for distance protection using support vector classification and support vector regression methods. The proposed method is evaluated by the different series capacitor location in the transmission line, where a metal oxide varistor protects the series capacitor against over-voltages. Extensive simulation experiments show that the proposed protection scheme provides accurate tripping logic with good accuracy of fault location. Also, the non-tripping decision for external faults that occurred on adjacent uncompensated transmission...
TL;DR: In this article, a sensorless sliding-mode observer is developed based on the induction motor model in the stationary reference frame, which can be used to provide field orientation in sensorless control scheme.
Abstract: This article discusses the problem of state and rotor flux angle estimation for the induction motor drive and presents a sensorless sliding-mode observer that is developed based on the induction motor model in the stationary reference frame. The observer is realized using the measured motor voltages and currents; it can be used to provide field orientation in a sensorless control scheme. The observer estimates the stationary frame fluxes of the induction motor and is developed using switching (sliding-mode) terms based on the current mismatches. The novelty is the design method used: first, a sensored observer is constructed; second, the observer is made sensorless by replacing the speed with a speed estimate; last, a gain design is found that allows accurate estimation of the rotor flux angle. The observer is analyzed with Lyapunov-based methods. It is found that with the proposed design, when an inaccurate speed signal is used, the resulting flux estimates are in phase with the real fluxes—this...
TL;DR: In this article, a spectral energy function for fault detection during a power swing using a novel time frequency transform known as the S-transform, a variable windowed short-time Fourier transform, which combines the elements of short time Fourier and wavelet transform is presented.
Abstract: Fault during a power swing is a challenging task for the distance relay functioning This article presents a spectral energy function for fault detection during a power swing using a novel time frequency transform known as the S-transform, a variable windowed short-time Fourier transform, which combines the elements of short-time Fourier transform and wavelet transform Initially, the current signal is preprocessed using S-transform to generate the S-matrix and corresponding S-contours (time–frequency contours) The spectral energy content of the S-counters is used to register symmetrical and unsymmetrical faults during a power swing and, based on a set threshold on the spectral energy, the relay blocks during a power swing and issue of the tripping signal during fault The proposed technique is tested for different fault conditions during a power swing with possible variations in operating parameters, including the ability to identify the faults with a response time of 125 cycles from the fault
TL;DR: In this article, a modified inertial control scheme is proposed for a doubly fed induction generator that uses frequency deviations, instead of derivative of frequency, to provide fast active power injection, which arrests the fall in frequency during transient conditions.
Abstract: The increasing share of wind power in the generation mix may lead to serious threats to system frequency, as the wind unit does not provide inertia and isolates from the grid during disturbances. The adverse effects of disturbances can be mitigated if wind units also contribute to system inertia. This article analyzes the dynamic participation of a doubly fed induction generator based wind turbine in system frequency regulation. The modified inertial control scheme is proposed for a doubly fed induction generator that uses frequency deviations, instead of derivative of frequency, to provide fast active power injection, which arrests the fall in frequency during transient conditions. To enhance the participation of a doubly fed induction generator in frequency control, optimal values of the speed control parameters of a doubly fed induction generator based wind turbine have been obtained using the integral square error technique. Frequency-linked pricing control is used to provide secondary freque...
TL;DR: It is shown that the proposed fault-diagnosis system based on Bayesian networks with noisy-OR/AND nodes has many merits, such as rapid reasoning, less storage memory and processing time, easy correctness of diagnosing results, flexibility, and application into a large power station and its transmission lines for real-time fault diagnosis.
Abstract: This article proposes a simplified fault-diagnosis system based on Bayesian networks with noisy-OR/AND nodes to estimate the faulty item/section(s) of a large power station and its transmission lines. The proposed method utilizes the final information of protective relays and corresponding circuit breakers to construct the Bayesian fault diagnosis model for each section. The learning algorithm for Bayesian network parameters takes the sum of the mean-squared error between the expected values and the computed values of certain target variables as the minimizing optimization function to adjust the network parameters continuously. By comparing the result beliefs of possible faulty sections, the faulty item/section(s) becomes a candidate. In order to test the validity and feasibility of that method, a computer simulation of the High Dam power station and its 500-kV transmission lines is used. It is shown that the proposed diagnosis method has many merits, such as rapid reasoning, less storage memory ...
TL;DR: In this article, a hybrid islanding detection technique is proposed which uses average rate of voltage change and capacitor bank tap switching to detect islanding conditions with very small power mismatches in them.
Abstract: Distributed generators are acquiring more attention in power systems because they can avoid distribution and transmission upgrade requirements and improve power quality issues. Islanding is one of the problems that arise with integrating these resources into the distribution system. In this article, a novel hybrid islanding detection technique is proposed which uses average rate of voltage change and capacitor bank tap switching. The proposed method is tested on a real system and different load characteristics with different dependence coefficients to voltage and frequency are studied. The power system is perturbed only when the method suspects that islanding has occurred. The proposed method could detect islanding conditions with very small power mismatches in them.
TL;DR: A predator–prey-based optimization technique is applied to obtain the scheduling of a hydrothermal system with cascaded reservoirs, minimizing economic and gaseous pollutants and emission objectives.
Abstract: In this article, a predator–prey-based optimization technique is applied to obtain the scheduling of a hydrothermal system with cascaded reservoirs, minimizing economic and gaseous pollutants and emission objectives. These objectives are mutually conflicting and are equally important. Predator–prey optimization is a stochastic optimization technique based on the particle swarm optimization concept having an additional predator effect that helps to explore the search area more efficiently due to the fear created by the predator. A heuristic search technique is applied for generating an initial feasible solution. The direct substitution method is implemented to handle the equality constraints, whereby dependent variables are determined from the equality constraint. Inequality constraints of dependent variables are taken care by incorporating an additional objective function represented by the fuzzy membership index, and other variables are set to their limits on violation. Fuzzy methodology has bee...
TL;DR: In this article, a new solution using the semi-definite programming approach to solve the combined heat and power economic dispatch problem is presented. But the solution is not suitable for solving the problem with a large number of variables.
Abstract: This article presents a new solution using the semi-definite programming approach to solve the combined heat and power economic dispatch problem. The proposed method involves reformulating the combined heat and power dispatch problem into a semi-definite programming form. The resulting semi-definite programming problem is solved using the primal-dual solver. The effectiveness of the proposed method is illustrated through some test problems, and the results are compared with those in literature.
TL;DR: In this article, a vector space-based perspective is used to diagnose radial deformation and axial displacement of transformer windings, and the angular proximity index is used. But the results show that transfer functions of radially deformed and axially displaced windings are well separated visually in the reduced space.
Abstract: The transfer function is a well-known method to detect mechanical defects of transformer windings. After measurement of transfer functions, they must be evaluated to detect any anomaly in transformer windings. One of the main problems in this stage is lack of transparency. This article tries to solve this problem through a vector space-based perspective to diagnose radial deformation and axial displacement of transformer windings. To determine the severity of the winding deformation or displacement, the angular proximity index is used. The measurement results show the effectiveness of this index. Based on the verified model of the transformer, a dimensionality reduction technique is applied to transformer's transfer function to map it from its original high-dimensional vector space to a lower-dimensional one. It is shown that transfer functions of radially deformed and axially displaced windings are well separated visually in the reduced space.
TL;DR: In this paper, a manganese oxide-based aqueous super-capacitor was used to convert a conventional battery into a super battery and showed that the performance of the super-cameras can be improved through a new electrode, electrolyte materials, and issues related to the construction of the device.
Abstract: Electrical energy storage is a critical parameter in many advanced electric vehicles. Conventional batteries provide limited solution in this regard. Development of a battery compatible super-capacitor can give a good hybrid energy storage system consisting of a battery and super-capacitor. An aqueous metal oxide super-capacitor is voltage compatible with a conventional battery. Advances are required in improving both the energy and power density of this super-capacitor through a new electrode, electrolyte materials, and issues related to the construction of the device. Modeling with electrical parameters as an output and electrode/ electrolyte parameters as an input can be very effective in developing a low-cost super-capacitor. Electrode construction and material play important roles in its performance; these two aspects have been addressed in this article through a modeling approach to convert a manganese oxide-based aqueous super-capacitor into a cost-effective product. New super-capacitor st...
TL;DR: In this article, a modified particle swarm optimization (MPSO) method is proposed for optimal planning of active power line conditioners in a distribution network that is polluted by non-linear loads.
Abstract: Optimal allocation and sizing of active power line conditioners in a distribution network is a discrete and non-linear problem. Heuristic-based optimization methods are reliable approaches for solving these types of problems, particularly for a large-scale distribution network. However, the optimization parameters in heuristic methods can influence the final solution significantly so that if these parameters are selected improperly, the risk of trapping in local minima may be remarkable. In this article, a new method—modified particle swarm optimization—is proposed for optimal planning of active power line conditioners in a distribution network that is polluted by non-linear loads. In this method, external particle swarm optimization is used to determine the main particle swarm optimization parameters accurately. To validate the performance of the proposed method, a 6-bus and the IEEE 18-bus test systems are employed. Different scenarios are studied, and the results are compared with those obtain...
TL;DR: In this article, the authors discussed the characteristics of voltage dip associated with line-to-ground and lineto-line faults and presented a new method to detect type B and D with the help of positive-and negative-sequence potential gradient methods derived as a function of distance to fault location.
Abstract: The majority of faults on a utility system are line-to-ground faults, and it is also the most common cause of voltage dips in industrial system. The disruption of an industrial process due to a line-to-ground fault can result in substantial costs to operation. The dip in the single phase associated with this fault is either type B or D. However, type D is also associated with to line-to-line faults. For the application of a suitable mitigation scheme to voltage dips, it is essential to distinguish between type B and D from measured sag voltages. This article discusses the characteristics of dips associated with line-to-ground and line-to-line faults and presents a new method to detect type B and D with the help of positive- and negative-sequence potential gradient methods derived as a function of distance to fault location. The need to distinguish type B and D, and the advantages of characterization through the sequence component, are also discussed.
TL;DR: In this paper, an efficient off-line identification method for induction machines by a real-coded genetic algorithm is presented, which minimizes the output error between the current acquired experimentally from the induction machine and the computed one from the adopted model at the same instance.
Abstract: This article presents an efficient off-line identification method for induction machines by a real-coded genetic algorithm. Using only the starting current and the corresponding phase voltage, the electrical and mechanical parameters are estimated simultaneously. This is achieved by minimization of the quadratic output error between the current acquired experimentally from the induction machine and the computed one from the adopted model at the same instance. To improve real-coded genetic algorithm performance and avoid a risk of premature convergence, a dynamic selection based on quadratic ranking is proposed for varying the selection pressure across the generation evolution. A comparison of the different real-coded genetic algorithms—the proposed, linear ranking, Roulette wheel and Boltzmann real-coded genetic algorithms—is carried out on two motors' (1.5 and 0.4 kW) parameter estimation. The transient and steady-state computed current using the estimated parameters are best matched to the meas...
TL;DR: The combination of space-vector modulation and direct torque control is presented to reduce the torque ripple contents in a medium-power adjustable speed drive system of induction motor supplied by a five level diode-clamped inverter.
Abstract: The combination of space-vector modulation and direct torque control is presented in this article to reduce the torque ripple contents in a medium-power adjustable speed drive system of induction motor. The drive is supplied by a five level diode-clamped inverter. The results show improvement in the torque ripple contents compared with a conventional direct torque control scheme. The experimental results of output voltage of the system for a diode-clamped multi-level inverter are also presented.
TL;DR: In this paper, a decentralized reactive power controller for parallel operation of voltage source converters in an autonomous microgrid, which leads to the proper reactive power sharing, voltage regulation, and small signal stability margin in microgrids.
Abstract: Load sharing without communication between voltage source converters is most important for reliable operation of microgrids. The common approach to achieve this is using the conventional droop technique. Although this method shares a common active load, reactive power sharing is strongly affected by system parameters. In addition, there is an inherent trade-off between the reactive power-sharing accuracy, voltage regulation, and small signal stability margin. This article presents a novel decentralized reactive power controller for parallel operation of voltage source converters in an autonomous microgrid, which leads to the proper reactive power sharing, voltage regulation, and small signal stability margin in microgrids. The proposed methodology and other reactive power-sharing controllers are simulated in IEEE 37-bus test system, and the multi-objective optimization method is used to optimum tuning of each controller and comparison against each other. Simulation results show better performance...