Journal of Operation and Automation in Power EngineeringJournal of Operation and Automation in Power Engineering
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Feed provided by Journal of Operation and Automation in Power Engineering. Click to visit.Performance Improvement of Single-Phase Transformerless Grid-Connected PV Inverters Regarding ...
http://joape.uma.ac.ir/article_736_144.html
The single-phase transformerless grid-connected photovoltaic (PV) systems, mainly the low-power single-phase systems, require high efficiency, small size, lightweight, and low-cost grid-connected inverters. However, problems such as leakage current, the DC current injection and safety issues are incorporated with transformerless grid-connected PV inverters. Besides, the new standards such as Low-Voltage Ride-Through (LVRT) capability and staying connected to the grid during the fault occurrence should be considered for the next generation of transformerless PV inverters. In this paper, a study is going underway on the LVRT capability and the Common-Mode Voltage (CMV) in a number of most common transformerless grid-connected PV inverters. In fact, by a comprehensive study on all possible switching combinations and the current paths during the freewheeling period of the selected inverters, the proposed control strategy for performance improvement of the PV inverters under the normal and the LVRT conditions is presented. As a matter of fact, a reconfigurable PWM method is proposed, which makes it possible to switch between two PWM methods and hence provide improved performance of the inverters in the LVRT condition. Finally, the results of simulations in the normal and the LVRT operations to verify the theoretical concepts are indicated.Tue, 30 Apr 2019 19:30:00 +0100A two-stage stochastic programming model for the optimal sizing of hybrid PV/diesel/battery in ...
http://joape.uma.ac.ir/article_737_144.html
Ships play the major role in bulk transportation and they need their special energy system. This paper proposes a stochastic programing method for optimal sizing of a hybrid ship power system with energy storage system (ESS), photovoltaic power (PV) and diesel generator. To account for uncertainties, in this study a two-stage stochastic mixed-integer non-linear programing is used to model the optimal design problem of hybrid system for ships. The uncertainty of the hourly global solar irradiation and its effect on the output power of the PV system is taken into account. The probability density function of the global solar radiation follows a normal distribution. The Monte Carlo sampling approach is used to generate the scenarios with a specified probability and a proper scenario reduction method is used to decrease the computational burden of problem. Three cases are studied and the results are presented and compared.Tue, 30 Apr 2019 19:30:00 +0100Unit commitment by a fast and new analytical non-iterative method using IPPD table and ...
http://joape.uma.ac.ir/article_738_144.html
Many different methods have been presented to solve unit commitment (UC) problem in literature with different advantages and disadvantages. The need for multiple runs, huge computational burden and time, and poor convergence are some of the disadvantages, where are especially considerable in large scale systems. In this paper, a new analytical and non-iterative method is presented to solve UC problem. In the proposed method, improved pre-prepared power demand (IPPD) table is used to solve UC problem, and then analytical “λ-logic” algorithm is used to solve economic dispatch (ED) sub-problem. The analytical and non-iterative nature of the mentioned methods results in simplification of the UC problem solution. Obtaining minimum cost in very small time with only one run is the major advantage of the proposed method. The proposed method has been tested on 10 unit and 40-100 unit systems with consideration of different constraints, such as: power generation limit of units, reserve constraints, minimum up and down times of generating units. Comparing the simulation results of the proposed method with other methods in literature shows that in large scale systems, the proposed method achieves minimum operational cost within minimum computational time.Tue, 30 Apr 2019 19:30:00 +0100Day-ahead economic dispatch of coupled desalinated water and power grids with participation of ...
http://joape.uma.ac.ir/article_739_144.html
Nowadays, water and electricity are closely interdependent essential sources in human life that affect socio-economic growth and prosperity. In other words, electricity is a fundamental source to supply a seawater desalination process, while fresh water is used for cooling this power plant. Therefore, mutual vulnerability of water treatment and power generation systems is growing because of increased potable water and electricity demands especially during extremely-hot summer days. Hence, this paper presents a novel framework for optimal short-term scheduling of water-power nexus aiming to minimize total seawater desalination and electricity procurement cost while satisfying all operational constraints of conventional thermal power plants, co-producers and desalination units. Moreover, advanced adiabatic compressed air energy storage (CAES) with no need to fossil fuels can participate in energy procurement process by optimal charging during off-peak periods and discharging at peak load hours. A mixed integer non-linear programming (MINLP) problem is solved under general algebraic mathematical modeling system to minimize total water treatment cost of water only units and co-producers, total fuel cost of thermal power plants and co-generators. Ramp up and down rates, water and power generation capacities and balance criteria have been considered as optimization constraints. It is found that without co-optimization of desalination and power production plants, load-generation mismatch occurs in both water and energy networks. By incorporating CAES in water-power grids, total fuel cost of thermal units and co-producers reduce from $1222.3 and $24933.2 to $1174.8 and $24636.8, respectively. In other words, application of CAES results in $343.9 cost saving in benchmark water-power hybrid grid.Tue, 30 Apr 2019 19:30:00 +0100High gain multi-input DC-DC converter with combined phase-shift/PWM modulation for stand-alone ...
http://joape.uma.ac.ir/article_740_144.html
The existence of unreliable renewable energy resources would be required to use energy resources and storage units simultaneously, particularly in applications such as electrical vehicles and stand-alone energy supplying systems. The objective of this paper is to introduce a new topology of multi input converter in hybrid power supply system of photovoltaic, fuel cell and battery for medium power applications. In this converter, the current ripple is eliminated, due to the presence of the coupled inductor. On the other hand, the probability to achieve a high voltage efficiency, to develop a high voltage DC link, will be achieved by using two transformers, which their terminals are in series. Since a combination of the magnetizing and the leakage inductors of these two transformers are used, there will be a zero voltage switching for switches, and also a soft switching for the output diodes, because of the presence of the leakage inductor in the secondary side of transformers. Steady state model and control system is discussed for the proposed converter. A 200 watt experimental prototype has been made in laboratory to evaluate the proposed converter.Tue, 30 Apr 2019 19:30:00 +0100Comprehensive Parametric Study for Design Improvement of a Low-Speed AFPMSG for Small Scale ...
http://joape.uma.ac.ir/article_741_144.html
In this paper, a comprehensive parametric analysis for an axial-flux permanent magnet synchronous generator (AFPMSG), designed to operate in a small-scale wind-power applications, is presented, and the condition for maximum efficiency, minimum weight and minimum cost is deduced. Then a Computer-Aided Design (CAD) procedure based on the results of parametric study is proposed. Matching between the generator side and turbine characteristics as well as the mechanical constraints is taken into account in design algorithm. A 2.5 kW AFPMSG with two parallel connected stators and surface mounted permanent magnets on its rotor disk is designed using the developed program, and then three dimensional finite-element analyses are carried out to validate the design procedure.Tue, 30 Apr 2019 19:30:00 +0100Adaptive Sliding Mode Control of Multi-DG, Multi-Bus Grid-Connected Microgrid
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This paper proposes a new adaptive controller for the robust control of a grid-connected multi-DG microgrid (MG) with the main aim of output active power and reactive power regulation as well as busbar voltage regulation of DGs. In addition, this paper proposes a simple systematic method for the dynamic analysis including the shunt and series faults that are assumed to occur in the MG. The presented approach is based on the application of the slowly time-variant or quasi-steady-state sequence networks of the MG. At each time step, the connections among the MG and DGs are shown by injecting positive and negative current sources obtained by controlling the DGs upon the sliding mode control in the normal and abnormal operating conditions of the MG. Performance of the proposed adaptive sliding mode controller (ASMC) is compared to that of a proportional-integral (PI)-based power controller and SMC current controller. The validation and effectiveness of the presented method are supported by simulation results in MATLAB-Simulink.Tue, 30 Apr 2019 19:30:00 +0100Optimal Sensorless Four Switch Direct Power Control of BLDC Motor
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Brushless DC (BLDC) motors are used in a wide range of applications due to their high efficiency and high power density. In this paper, sensorless four-switch direct power control (DPC) method with the sector to sector commutations ripple minimization for BLDC motor control is proposed. The main features of the proposed DPC method are: (1) fast dynamic response (2) easy implementation (3) use of power feedback for motor control that is much easy to implement (4) eliminating the torque dips during sector-to sector commutations. For controlling the motor speed, a position sensorless method is used enhancing drive reliability. For reference speed tracking, a PI control is also designed and tuned based on imperialist competition algorithm (ICA) that reduces reference tracking error. The feasibility of the proposed control method is developed and analyzed by MATLAB/SIMULINK®. Simulation results prove high performance exhibited by the proposed DPC strategy.Tue, 30 Apr 2019 19:30:00 +0100An Interleaved Configuration of Modified KY Converter with High Conversion Ratio for Renewable ...
http://joape.uma.ac.ir/article_753_144.html
In this paper, a new high efficiency, high step-up, non-isolated, interleaved DC-DC converter for renewable energy applications is presented. In the suggested topology, two modified step-up KY converters are interleaved to obtain a high conversion ratio without the use of coupled inductors. In comparison with the conventional interleaved DC-DC converters such as boost, buck-boost, SEPIC, ZETA and CUK, the presented converter has higher voltage gain that is obtained with a suitable duty cycle. Despite the high voltage gain of the proposed converter, the voltage stress of the power switches and diodes is low. Therefore, switches with low conduction losses can be applied to improve the converter efficiency. Moreover, due to utilization of interleaving techniques, the input current ripple is low which makes the suggested converter a good candidate for renewable energy applications such as PV power system. Operation principle and steady-state analysis of the proposed converter in continuous conduction mode (CCM) and discontinuous conduction mode (DCM) are discussed in detail. Also, theoretical efficiency of the proposed converter is calculated. Finally, in order to evaluate the proposed converter operation by a renewable energy source such as a PV, the simulation results are presented. Moreover, a 220W prototype of the presented DC-DC converter is designed and implemented in the laboratory to verify its performance.Tue, 30 Apr 2019 19:30:00 +0100Mini/Micro-Grid Adaptive Voltage and Frequency Stability Enhancement Using Q-learning Mechanism
http://joape.uma.ac.ir/article_764_144.html
This paper develops an adaptive control method for controlling frequency and voltage of an islanded mini/micro grid (M/µG) using reinforcement learning method. Reinforcement learning (RL) is one of the branches of the machine learning, which is the main solution method of Markov decision process (MDPs). Among the several solution methods of RL, the Q-learning method is used for solving RL in this paper because it is a model-free strategy and has a simple structure. The proposed control mechanism is consisting of two main parts. The first part is a classical PID controller which is fixed tuned using Salp swarm algorithm (SSA). The second part is a Q-learning based control strategy which is consistent and updates it's characteristics according to the changes in the system continuously. Eventually, the dynamic performance of the proposed control method is evaluated in a real M/µG compared to fuzzy PID and classical PID controllers. The considered M/µG is a part of Denmark distribution system which is consist of three combined heat and power (CHP) and three WTGs. Simulation results indicate that the proposed control strategy has an excellent dynamic response compared to both intelligent and traditional controllers for damping the voltage and frequency oscillations.Tue, 30 Apr 2019 19:30:00 +0100Operation of multi Carrier microgrid (MCMG) considering demand response
http://joape.uma.ac.ir/article_765_144.html
: In this paper, the operation of a future distribution network is discussed under the assumption of a multi-carrier microgrid (MCMG) concept. The new model considers a modern energy management technique in electricity and natural gas networks based on a novel demand side management (DSM) which the energy tariff for responsive loads are correlated to the energy input of the network and changes instantly. The economic operation of MCMG is formulated as an optimization problem. In conventional studies, energy consumption is optimized from the perspective of each infrastructure user without considering the interactions. Here, the interaction of energy system infrastructures is considered in the presence of energy storage systems (ESSs), small-scale energy resources (SSERs) and responsive loads. Simulations are performed using MCMG which consists of micro combined heat and power (CHP), photovoltaic (PV) arrays, energy storage systems (ESSs), and electrical and heat loads in grid-connected mode. Results show that the simultaneous operation of various energy carriers leads to a better MCMG performance. Moreover, it has been indicated that energy sales by multi sources to main grids can undoubtedly reduce the total operation cost of future networks.Tue, 30 Apr 2019 19:30:00 +0100An Isolated Off-Line High Power Factor Electrolytic Capacitor-Less LED Driver with Pulsating ...
http://joape.uma.ac.ir/article_766_144.html
One of the most efficient lighting technology is based on light-emitting diodes (LEDs). Common LED drivers with AC-input (50-60Hz) usually require a bulk electrolytic capacitor to decrease low-frequency ripple in the output. However, the critical element that limits the lifespan of the LED driver is the electrolytic capacitor. An isolated off-line LED driver is proposed in this paper, in which the required output capacitance is reduced so that the electrolytic capacitor can be omitted from the driver structure. The driver’s configuration and controlling method provide a high input power factor. Just a single switch and therefore a single controlling IC have been used in the proposed structure. The input power factor correction is implemented utilizing a boost-based method, and a novel structure is introduced for dc/dc conversion section. Power factor correction and dc/dc conversion are performed employing a simplistic and single controlling system. The output current feeding the LEDs is a high frequency pulsating current. Calculations, simulations and experimental waveforms of a laboratory prototype are presented to confirm the validity of the proposed driver.Tue, 30 Apr 2019 19:30:00 +0100Optimal Short-Term Coordination of Desalination, Hydro and Thermal Units
http://joape.uma.ac.ir/article_767_0.html
Nowadays, water and electricity are closely interdependent essential sources in human life that affect socio-economic growth and prosperity. Hence, this papers presents a novel framework for optimal short-term scheduling of water-power nexus aiming to minimize total seawater desalination and electricity procurement cost while satisfying all operational constraints of conventional thermal power plants, co-producers of potable water and power, desalination processes and hydro units. A mixed integer non-linear programming problem is developed under general algebraic mathematical modeling system (GAMS) optimization package to minimize total desalination cost of water only units and co-producers, total fuel cost of thermal power plants, co-generators, and hydro units considering ramp up and down rates of thermal units, water and electricity generation capacities, balance constraints, relationship between the released/spilled water and the water head of the reservoir with output power of hydro power plant.Fri, 17 May 2019 19:30:00 +0100Compensation of Voltage and Current Harmonics in Hybrid Renewable Energy System Using ...
http://joape.uma.ac.ir/article_768_0.html
In this paper, an adaptive control strategy is proposed for the inverters of renewable energy source (RES) to simultaneously control the load voltage, grid current and the amount of instantaneous injected power to the grid in the presence of grid voltage distortions and nonlinearity of load current. In the proposed control strategy, the power quality of the local load can be settled based on the operator command. In order to implement the proposed control strategy, a cascaded framework of power, voltage and current control has been introduced. An efficient and fast response controller is introduced for the voltage loop, aiming to compensate of harmonics without any complex calculations. The proposed cascade framework is simulated with nonlinear load and non-ideal grid conditions. The simulation results show the effectiveness of the proposed control strategy to not only supply the local load on an appropriate voltage and current quality but also maintaining the amount of injected power at the operator’s desired level.Fri, 17 May 2019 19:30:00 +0100Resilient operation scheduling of microgrid using stochastic programming considering demand ...
http://joape.uma.ac.ir/article_769_0.html
Resilient operation of microgrid is an important concept in modern power system. Its goal is to anticipate and limit the risks, and provide appropriate and continuous services under changing conditions. There are many factors that cause the operation mode of micogrid changes between island and grid-connected modes. On the other hand, nowadays, electric vehicles (EVs) are desirable energy storage systems (ESSs) because of clean transportation. Besides, energy storage systems are helpful to decrease power generation fluctuations arising from renewable energy sources (RESs) in new power systems. In addition, both sides (EV and RESs’ owners) can gain a good profit by integrating EVs and RESs. Therefore, in this paper, a resilient operation model for microgrid is presented considering disasters and islands from the grid. In the proposed formulation, microgrid (MG) operator schedules its energy resources, EVs and ESSs in minimum cost considering demand response (DR) program and resiliency of the microgrid to islanding and uncertainties in market price, load, and generation of RESs. The impact of uncertainties is modeled in the scenario based framework as stochastic programming. The efficiency of presented method is validated on IEEE standard test system and discussed in two cases.Fri, 17 May 2019 19:30:00 +0100A Repetitive Control- based Approach for Power Sharing among Boost Converters in DC Microgrids
http://joape.uma.ac.ir/article_770_0.html
In this paper a repetitive control (RC) approach to improve current sharing between parallel-connected boost converters in DC microgrids is presented. The impact of changes in line impedance on current sharing is investigated. A repetitive controller is designed and connected in series with current controller of the boost converters to control the switching signals such that by regulating of the output voltage of each converter, the circulating current is minimized. The performance of the proposed control strategy is validated through simulation.Fri, 17 May 2019 19:30:00 +0100Maximum Power Point Tracker for Photovoltaic Systems Based on Moth-Flame Optimization ...
http://joape.uma.ac.ir/article_771_0.html
The performance of photovoltaic (PV) systems is highly dependent on environmental conditions. Due to probable changes in environmental conditions, the real-time control of PV systems is essential for exploiting their maximum possible power. This paper proposes a new method to track the maximum power point of PV systems using the moth-flame optimization algorithm. In this method, the PV DC-DC converter’s duty cycle is considered as the optimization parameter, and the delivered power of the PV system is maximized in real time. In the proposed approach, some schemes are also employed for detecting condition changes and ignoring small fluctuations of the duty cycle. The results of performance evaluation confirm that the proposed method is very fast, robust, and accurate in different conditions such as standard irradiance and temperature, irradiance and temperature variations, and partial shading conditions. The obtained steady-state efficiency and response time for the introduced method under the standard conditions of the test PV system are 99.68% and 0.021 s, respectively. Indeed, in addition to a relatively good efficiency, the faster response of the introduced tracker is also evident in comparison with other methods.Fri, 17 May 2019 19:30:00 +0100Electrical Load Manageability Factor analyses by Artificial Neural Network Training
http://joape.uma.ac.ir/article_772_0.html
On typical medium voltage feeder, Load side management means power energy consumption controlling at connected loads. Each load has various amount of reaction to essential parameters variation that collection of these reactions is mentioned feeder behavior to each parameter variation. Temperature, humidity, and energy pricing variation or major event happening and power utility announcing to the customers are essential parameters that are considered at recent researches. Depends on amount of improvement that each changeable parameters effect on feeder load consumption, financial assets could be managed correctly to gain proper load side management. Collecting feeder loads behavior to all mentioned parameters will gain Load Manageability Factor (LMF) that helps power utilities to manage load side consumption. Calculating this factor needs to find out each types of load with unique inherent features behavior to each parameters variation. This paper and future works will help us to catch mentioned LMF. In this paper analysis of typical commercial feeder behavior due to temperature and humidity variation with training artificial neural network will be done. Load behavior due to other essential parameters variations like energy pricing variation, major event happening, and power utility announcing to the customers, and etc will study in future worksFri, 17 May 2019 19:30:00 +0100A Bi-Level Optimization Approach for Optimal Operation of Distribution Networks with Retailers ...
http://joape.uma.ac.ir/article_773_0.html
Distributed energy resources (DERs) including distributed generators (DGs) and controllable loads (CLs) are managed in the form of several microgrids (MGs) in active distributions networks (ADNs) to meet the demand locally. On the other hand, some loads of distribution networks (DNs) can be supplied by retailers which participate in wholesale energy markets. Therefore, there are several decision makers in DNs which their cooperation should be modeled for optimal operation of the network. For this purpose, a bi-level optimization approach is proposed in this paper to model the cooperation between retailers and MGs in DNs. In the proposed model, the aim of the upper level (leader) and lower level (follower) problems are to maximize the profit of retailers and to minimize the cost of MGs, respectively. To solve the proposed multi-objective bi-level optimization model, multi-objective Particle Swarm Optimization (MOPSO) algorithm is employed. The effectiveness of the proposed bi-level model and its solution methodology is investigated in the numerical results.Fri, 17 May 2019 19:30:00 +0100Optimal energy management of microgrid in day-ahead and intra-day markets using a copula-based ...
http://joape.uma.ac.ir/article_774_0.html
Recently, economic and environmental problems have created a strong attitude toward utilizing renewable energy sources (RESs). Nevertheless, uncertainty of wind and solar power leads to a more complicated energy management (EM) of RESs in microgrids. This paper models and solves the EM problem of microgrid from the generation point of view. To do this, mathematical formulation of a grid- connected microgrid including wind turbine (WT), photovoltaic (PV), micro turbine (MT), fuel cell (FC) and energy storage system (ESS) is presented. Furthermore an improved incentive-based demand response program (DRP) is applied in microgrid EM problem to flatten the load pattern. Comprehensive studying of EM in both intra-day and day-ahead markets is another contribution of this paper. However, the main novelty of this paper is proposing a new uncertainty modeling technique which is based on copula function and scenario generation. This paper tries to optimize operational cost and environmental pollution as the objective functions and solve them using group search optimization (GSO) algorithm. Numerical results approve the efficiency of the proposed method in solving microgrid EM problem.Fri, 17 May 2019 19:30:00 +0100