S.K. Gupta; J.M. Tripathi; A. Ranjan; R. Kesh; A. Kumar; M. Ranjan; P. Sahu
Abstract
In the family of Flexible AC Transmission Systems (FACTS) controllers, the distributed power flow controller (DPFC) can control powerfully all the system's parameters like bus voltages magnitude, transmission angle, and line impedances with high redundancy and a wide range of compensation. In this paper, ...
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In the family of Flexible AC Transmission Systems (FACTS) controllers, the distributed power flow controller (DPFC) can control powerfully all the system's parameters like bus voltages magnitude, transmission angle, and line impedances with high redundancy and a wide range of compensation. In this paper, IEEE-14 bus IEEE-30 bus, and IEEE-118 bus systems are taken for the testing of the proposed approach. The optimal placement of the series and shunt converters of the DPFC is decided by the most critical bus and most critical line associated with that bus respectively. The sizing of the DPFC is decided based on the minimization of active power losses of the systems. The loss function is considered an objective function and the limits of the bus voltages magnitudes, bus voltage angles, thermal limits of the lines, and level of compensation of the DPFC are taken as the system's constraints. To solve complex problems in various fields, meta-heuristic optimizations are more popular. Among the meta-heuristic optimizers, the jellyfish optimizer is one that is based on the behavior of jellyfish in the ocean. The optimization of the objective function with constraints has been solved by time-varying acceleration coefficients (TVAC) particle swarm optimization (PSO), artificial bee colony (ABC), genetic algorithm (GA), and metaheuristic optimizer jellyfish methods. Results show that all the optimization techniques provide solutions with minimum losses. Among these methods, the solution of the jellyfish optimizer has the lowest active power losses, highest convergence rate, less number of iterations, and also takes less computational time.
Power System Operation
S.M. Mohseni-Bonab; A. Rabiee; S. Jalilzadeh; B. Mohammadi-Ivatloo; S. Nojavan
Volume 3, Issue 1 , June 2015, , Pages 83-93
Abstract
Optimal Reactive Power Dispatch (ORPD) is a multi-variable problem with nonlinear constraints and continuous/discrete decision variables. Due to the stochastic behavior of loads, the ORPD requires a probabilistic mathematical model. In this paper, Monte Carlo Simulation (MCS) is used for modeling of ...
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Optimal Reactive Power Dispatch (ORPD) is a multi-variable problem with nonlinear constraints and continuous/discrete decision variables. Due to the stochastic behavior of loads, the ORPD requires a probabilistic mathematical model. In this paper, Monte Carlo Simulation (MCS) is used for modeling of load uncertainties in the ORPD problem. The problem is formulated as a nonlinear constrained multi objective (MO) optimization problem considering two objectives, i.e., minimization of active power losses and voltage deviations from the corresponding desired values, subject to full AC load flow constraints and operational limits. The control variables utilized in the proposed MO-ORPD problem are generator bus voltages, transformers’ tap ratios and shunt reactive power compensation at the weak buses. The proposed probabilistic MO-ORPD problem is implemented on the IEEE 30-bus and IEEE 118-bus tests systems. The obtained numerical results substantiate the effectiveness and applicability of the proposed probabilistic MO-ORPD problem.
Electric Mechinces & Drive
Mehdi Bigdeli; Davood Azizian; Ebrahim Rahimpour
Volume 4, Issue 1 , June 2016, , Pages 83-92
Abstract
Nowadays, the most generated electrical energy is consumed by three-phase induction motors. Thus, in order to carry out preventive measurements and maintenances and eventually employing high-efficiency motors, the efficiency evaluation of induction motors is vital. In this paper, a novel and efficient ...
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Nowadays, the most generated electrical energy is consumed by three-phase induction motors. Thus, in order to carry out preventive measurements and maintenances and eventually employing high-efficiency motors, the efficiency evaluation of induction motors is vital. In this paper, a novel and efficient method based on Improved Big Bang-Big Crunch (I-BB-BC) Algorithm is presented for efficiency estimation in the induction motors. In order to estimate the induction motor’s efficiency, the measured current, the power factor and the input power are applied to the proposed method and an appropriate objective function is presented. The main advantage of the proposed method is efficiency evaluation of induction motor without any intrusive test. Moreover, a new effective and improved version of BB-BC algorithm is introduced. The presented modifications can improve the accuracy and speed of the classic version of algorithm. In order to demonstrate the capabilities of the proposed method, a comparison with other traditional methods and intelligent optimization algorithms is performed.
Energy Management
Sh. Shadi; J. Salehi; A. Safari
Abstract
Energy management (EM) in smart distribution networks (SDN) is to schedule the power transaction between the SDN and the existing distributed energy resources (DERs) e.g., distributed generations, especially renewable resources and electrical vehicles, from an eco-technical viewpoint. Due to the dual ...
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Energy management (EM) in smart distribution networks (SDN) is to schedule the power transaction between the SDN and the existing distributed energy resources (DERs) e.g., distributed generations, especially renewable resources and electrical vehicles, from an eco-technical viewpoint. Due to the dual role of electric vehicles (EVs) acting as a power source and load, they presented both challenges and opportunities in EM. The complexity of EM increases as DERs become more prevalent in SDN. Moreover, the uncertainties of renewable resources, price, and load besides the uncertainties related to the place, amount, and time of EV’s charging makes EM a more intricate field. This supports the necessity of extensive tools and approaches to manage EM in SDNs. In this respect, this paper proposes an optimum scenario-based stochastic energy management scheme for intelligent distribution networks. The proposed approach is modeled as a MINLP problem and solved in GAMS software under the DICOPT solver. The test is conducted on a 33-bus SDN with and without factoring in uncertainties.
M. Moazen; M. Sabahi
Volume 2, Issue 2 , December 2014, , Pages 141-150
Abstract
Using an Electric Differential (ED) in electric vehicle has many advantages such as flexibility and direct torque control of the wheels during cornering and risky maneuvers. Despite its reported successes and advantages, the ED has several problems limits its applicability, for instance, an increment ...
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Using an Electric Differential (ED) in electric vehicle has many advantages such as flexibility and direct torque control of the wheels during cornering and risky maneuvers. Despite its reported successes and advantages, the ED has several problems limits its applicability, for instance, an increment of control loops and an increase of computational effort. In this paper, an electric differential for an electric vehicle with four independent driven motors is proposed. The proposed ED is easy-to-implement and hasn’t the problems of previous EDs. This ED has been developed for four wheels steering vehicles. The synchronization action is achieved by using an improved fictitious master technique, and the Ackerman principle is used to compute an adaptive desired wheel speed. The proposed ED is simulated and the operation of the system is studied. The simulation results show that ED ensures both reliability and good path tracking.
J. Fallah Ardeshir; A. Ajami; A. Jalilvand; A. Mohammadpour
Volume 1, Issue 2 , November 2013, , Pages 147-155
Abstract
This paper proposes a Flexible Power Electronic Transformer (FPET) for the application in the micro-grids. The low frequency transformer is usually used at the Point of Common Coupling (PCC) to connect the low voltage grid and utility network to each other. The conventional 50Hz transformer results in ...
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This paper proposes a Flexible Power Electronic Transformer (FPET) for the application in the micro-grids. The low frequency transformer is usually used at the Point of Common Coupling (PCC) to connect the low voltage grid and utility network to each other. The conventional 50Hz transformer results in enhanced low voltage-grid power management system during grid-connected operation. In this paper, the whole system represented as two, three-phase AC systems with an intermediate high-frequency transformer for power flow controlling. The FPET consists of a high frequency transformer and three-phase to single-phase matrix converter. The matrix converters are modulated with a Pulse Width Modulation (PWM) strategy for a bi-directional power flow control. Phase shift modulation strategy in two sides of FPET is used for power flow controlling by PI controller from utility network to low voltage grid and vice versa. FPET model is established in Matlab/Simulink software with controller for power flow controlling. Presented simulation results have shown the validity of the proposed control system for FPET through the Matlab/Simulink simulation.
F. Shamsini Ghiasvand; K. Afshar; N. Bigdeli
Abstract
In the restructured electricity industry, the electricity retailer, as a profit-oriented company, buys electricity from wholesale electricity markets and sells it to end customers. On the other hand, with the move of the electricity networks towards smart grids, small customers who, in addition to receiving ...
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In the restructured electricity industry, the electricity retailer, as a profit-oriented company, buys electricity from wholesale electricity markets and sells it to end customers. On the other hand, with the move of the electricity networks towards smart grids, small customers who, in addition to receiving energy from the distribution network, can generate power on a small scale, have emerged as prosumers in the electricity market environment. Therefore, the prosumers' aggregator is defined to maximize the profit of a set of prosumers in this environment. In this paper, the energy exchange between the retailer and the aggregator has been modeled as a bi-level game. At a higher level, the retailer, as a leader to maximize its profit or minimize its expenses, offers a price to buy or sell energy to the prosumers' aggregator. The aggregator also decides on the amount of exchange energy to buy or sell, to minimize the energy supply costs required of its consumers according to the retailer's bid price. In this paper, a combined method based on~MILP (Mixed Integer Linear Programming)~and MO (Mayfly Optimization) has been used to find the optimal point of this modeled game. To evaluate the efficiency of the proposed method, the three pricing methods FP (Fixed Pricing),~TOU (Time Of Using), and RTP (Real Time Pricing) as price-based demand response programs have been compared using the proposed algorithm. The simulation results show that among the three pricing methods for customers, the RTP pricing method has the highest profit for the retailer and the lowest cost for the aggregator.
Distribution Systems
B. Mohammadzadeh; A. Safari; S. Najafi Ravadanegh
Volume 4, Issue 2 , December 2016, , Pages 165-174
Abstract
This paper presents a new and useful methodology for simultaneous allocation of sectionalizer switches and distributed energy resources (DERs) considering both reliability and supply security aspects. The proposed algorithm defines the proper locations of sectionalizer switching devices in radial distribution ...
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This paper presents a new and useful methodology for simultaneous allocation of sectionalizer switches and distributed energy resources (DERs) considering both reliability and supply security aspects. The proposed algorithm defines the proper locations of sectionalizer switching devices in radial distribution networks considering the effect of DER units in the presented cost function and other optimization constraints such as providing the maximum number of costumers to be supplied by DER units in islanded distribution systems after possible outages. In this paper, the main goal of cost function is to minimize the total cost of expected energy not supplied (EENS) with regard to impacts of load priority and optimum load shedding in the both grid connected and islanding states after possible outages. The proposed method is simulated and tested on a case study system in both cases of with DER and non DER situations. Also, this paper evaluates the number and amount of DER, switch and different DER penetration percentage effects in cost function value. For solving of mentioned problem, this paper uses a new and strong method based on imperialist competitive algorithm (ICA). Simulation and numerical results show the effectiveness of the proposed algorithm for placement of switch and DER units in the radial distribution network simultaneously.
Power Electronic
Ebrahim Babaei; Mohsen Hasan Babayi; Elias Shokati Asl; Sara Laali
Volume 3, Issue 2 , December 2015, , Pages 167-184
Abstract
In this paper, a new topology for boost Z-source inverterbased on switched-inductor cell is proposed. The operating modes of the proposed inverter are analyzed and also a suitable control method to generate the trigger signals of the inverter is presented. Having a common earth between the input source ...
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In this paper, a new topology for boost Z-source inverterbased on switched-inductor cell is proposed. The operating modes of the proposed inverter are analyzed and also a suitable control method to generate the trigger signals of the inverter is presented. Having a common earth between the input source and inverter and capability to generate a higher voltage gain by using lower amounts of the duty cycles are some advantages of the proposed Z-source inverter. Comparison of the proposed inverter with conventional Z-source inverters is presented from different points of the view. Finally, the accuracy performance of the proposed inverter is reconfirmed through the simulation results in EMTDC/PSCAD software program.
Distribution Systems
S. Ghaemi; K. Zare
Abstract
The determination of practical and coherent policy to pin down the price in restructured distribution networks should be considered as a momentous topic. The present paper introduces a new method of distribution marginal price (DMP) calculation. The main aim of this paper is to evaluate the DMP for both ...
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The determination of practical and coherent policy to pin down the price in restructured distribution networks should be considered as a momentous topic. The present paper introduces a new method of distribution marginal price (DMP) calculation. The main aim of this paper is to evaluate the DMP for both producers and consumers separately. For this purpose, the first part of the procedure emphasizes a price by which the producers should sell their power. To meet this target, the share of each node plays a significant role in the total active loss of the network. The producers will make a substantial profit when their efficiency leads to decreasing the share of the node that is associated with the total loss. In the second part of the procedure, DMP is computed for the consumers. In this part, based on the distribution system operator’s decision about the obtained profit allocated to the consumers, their payment has been reduced. This method has been applied to the 33-Bus Distribution System. The results demonstrate the characteristic of the method which tends to encourage the distributed units to increase their output powers. This is the reason why the penetration of these units in the networks is an opportunity for consumers from an economic aspect in such a way that merchandising surplus (MS) becomes zero.
Energy Management
N. Eskandari; S. Jalilzadeh
Abstract
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, ...
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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 works
Power System Stability
M. Nasiri; J. Milimonfared; S. H. Fathi
Abstract
This paper presents a new nonlinear backstepping controller for a direct-driven permanent magnet synchronous generator-based wind turbine, which is connected to the power system via back-to-back converters. The proposed controller deals with maximum power point tracking (MPPT) in normal condition and ...
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This paper presents a new nonlinear backstepping controller for a direct-driven permanent magnet synchronous generator-based wind turbine, which is connected to the power system via back-to-back converters. The proposed controller deals with maximum power point tracking (MPPT) in normal condition and enhances the low-voltage ride-through (LVRT) capability in fault conditions. In this method, to improve LVRT capability, machine-side converter controls dc-link voltage and MPPT is performed by grid side converter. Hence, PMSG output power is reduced very fast and dc-link voltage variation is reduced. Due to nonlinear relationship between dc-link voltage and controller input, nonlinear backstepping controller has good performances. By applying the proposed controller, dc-link overvoltage is significantly decreased. The proposed controller has good performance in comparison with Proportional-Integral (PI) controller and Sliding Mode Controller (SMC). In asymmetrical faults, to decrease grid side active power oscillations, the nonlinear backstepping dual-current controller is designed for positive- and negative- sequence components. The simulation results confirm that the proposed controller is efficient in different conditions.
M. Sadeghighasami; M. Shafieirad; I. Zamani
Abstract
The purpose of this study is to present a practical approach in which the effect of performance degradation and instability factors such as exogenous disturbances, parametric uncertainties, time-varying delay, and unstable modes can reduce to the minimum possible amount in linear switched positive systems. ...
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The purpose of this study is to present a practical approach in which the effect of performance degradation and instability factors such as exogenous disturbances, parametric uncertainties, time-varying delay, and unstable modes can reduce to the minimum possible amount in linear switched positive systems. To reduce the effect of the mentioned destructive factors and to strengthen the robust design of switched positive systems, in this paper, instead of using the co-positive Lyapunov function along with the L1-gain, the quadratic Lyapunov-Krasovskii function utilized along with the L2-gain, which leads to the design of H_∞ performance. The latter method, especially when there is a requirement to estimate the parameters with the support of the output feedback approach by minimizing the interface parameters, provides the feasibility of designing a more convenient and efficient observer-based controller. The necessary and sufficient conditions for solving the problem concerning the positivity of the system, disturbance attenuation, and parametric uncertainties are expressed by two theories and implemented by the linear matrix inequality technique. The results of this technique's solution include the gains of the controller and observer. Considering that stable and unstable modes are in this system, it is necessary to guarantee the exponential stability of the whole system by the controllers and designing the average dwell-time switching regime. Finally, illustrative examples, including numerical, practical, and comparative, are presented to show the efficiency and performance of different aspects of the proposed approach. The smallness of the mean square error values in the example compared with the output feedback method in linear programming confirms the capabilities of the presented approach. For instance, the mean square error of the system output for the method of this paper is 0.008 and for the compared approach is 0.081.
Power System Operation
A. Niromandfam; A. Sadeghi Yazdankhah; R. Kazemzadeh
Abstract
The regulatory schemes currently used for reliability improvement have weaknesses in the provision of quality services based on the customers’ perspective. These schemes consider the average of the service as a criterion to incentivize or penalize the distribution system operators (DSOs). On the ...
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The regulatory schemes currently used for reliability improvement have weaknesses in the provision of quality services based on the customers’ perspective. These schemes consider the average of the service as a criterion to incentivize or penalize the distribution system operators (DSOs). On the other hand, most DSOs do not differentiate electricity services at the customer level, due to the status of the electricity grid and lack of adequate information about customers’ preferences. This paper proposes a novel reliability insurance scheme (RIS), which enables the electricity consumers to determine their desired reliability levels according to their preferences and pay corresponding premiums to the DSO. The DSO can use the premiums to improve reliability or reimburse consumers. To design efficient insurance contracts, this paper uses utility function to estimate customers’ viewpoints of electricity energy consumption. This function measures the customers’ satisfaction of electricity energy consumption. The proposed utility based reliability insurance scheme (URIS) may create a free-riding opportunity for the DSO, in which low quality service is provided and the collected premiums are used to pay the reimbursements. To prevent free-riding opportunity, this paper incorporates the proposed URIS and reward/penalty schemes (RPSs). The results show that the success of the proposed reliability scheme increases as the grid flexibility increases.
V. Rahi; A. Abdollahi; E. Heydarian-Forushani; M. Rashidinejad; A. Sheikhi Fini
Abstract
One of the most important challenges of smart grids is the congestion of transmission lines. A flexible smart grid with demand-side resources can be a suitable solution to manage transmission lines congestion. This paper proposes a multi-objective model with the aim of congestion management through generation ...
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One of the most important challenges of smart grids is the congestion of transmission lines. A flexible smart grid with demand-side resources can be a suitable solution to manage transmission lines congestion. This paper proposes a multi-objective model with the aim of congestion management through generation rescheduling considering cost and emission purposes in a flexible smart grid. An inconvenience cost for consumers is defined to model the consumers’ unsatisfactory as a consequence of participating in demand response programs (DRPs). Furthermore, a smart grid flexibility index (SGFI) has been presented to show the available flexibility of smart grid as a result of DRPs and gas turbine generators as fast response resources. The DRPs could increase the flexibility of the smart grids due to their impact on flattening the load curve, but this may cause some inconveniences for consumers. On the other hand, participation of consumers in DRPs and the power output gas turbine are associated with uncertainty. In this paper, the uncertainty of consumer's participation in the DRPs has been modeled by Fuzzy-Markov. The proposed multi-objective particle swarm optimization (MOPSO) has been implemented on the IEEE 30-bus system. The results show that the total operation cost including the generation cost, DRP cost, inconvenience cost of consumers, and pollution is reduced. In fact, the share of generation of expensive generators is reduced.
Distribution Systems
H. Fateh; A. Safari; S. Bahramara
Abstract
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 ...
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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.
Power Electronic
S. Jalilzadeh; M. Pakdel
Abstract
This paper presents a soft-switching DC-DC boost converter, which can be utilized in renewable energy systems such as photovoltaic array, and wind turbine connections to infinite bus of a big power network, using grid connected inverters. In the proposed topology for the DC-DC boost converter, the main ...
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This paper presents a soft-switching DC-DC boost converter, which can be utilized in renewable energy systems such as photovoltaic array, and wind turbine connections to infinite bus of a big power network, using grid connected inverters. In the proposed topology for the DC-DC boost converter, the main and the auxiliary power switches are turned on and turned off with zero voltage switching (ZVS) and zero current switching (ZCS), respectively. Furthermore, by applying soft-switching techniques to driving power switches, the power losses and stresses associated with commutation of power devices decrease significantly. The efficiency of the proposed soft-switched DC-DC converter at various output powers is compared with that of the traditional DC-DC converter and a few topologies proposed in recent literature. This comparison indicates that the proposed DC-DC boost converter is much more efficient around the rated power (1 kW). The power topology and the control strategy applied to the proposed soft-switched DC-DC boost converter, which is connected to a grid-tied inverter, are analyzed theoretically by simulation studies. Moreover, an experimental prototype is implemented to verify the theoretical analysis and the simulation studies.
G.V.B. Chary; K. Roslina
Abstract
Today, commercial simulation packages can have the capability of solving complex power system networks by using various transmission line models. When there is a change in the modeling routine of transmission lines, their accuracy is also changese main aim of this paper is to compare lumped PI and distribute ...
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Today, commercial simulation packages can have the capability of solving complex power system networks by using various transmission line models. When there is a change in the modeling routine of transmission lines, their accuracy is also changese main aim of this paper is to compare lumped PI and distribute CP transmission line models in terms of accuracy and optimization capability. The IEEE 57 bus time domain power system models are designed by using these transmission line models for analysis in this paper. In these proposed systems the transmission line parameters are described as frequency independent. Therefore, in CP lines the Clark's transformation method does not provide exact decoupling of lines, to achieve exact decoupling of lines and accuracy the lines are continuously transposed in proposed systems. The NR load flow analysis was used for error estimation in balanced and unbalanced networks. The results had reported voltage error at the buses, transmission line error as function of line length and frequency response of line parameters. The frequency study of the line parameters was shown the PI lines system behaves as low pass filter and the CP lines system behaves as high pass filter. In this paper, also studied the optimization of proposed models by using a well-known Ant Lion Optimization (ALO) algorithm to set control variables, such as generator voltages, position of tap changing transformers and shunt capacitor banks. The optimization results of total power loss, voltage deviation and voltage stability index were compared with other algorithms. The results revealed that the ALO has best cothe nvergence characteristics and best elitism phase. Therefore, the CP lines system had shown considerable improvements of optimization results.
Electric Mechinces & Drive
S. Hajiaghasi; Z. Rafiee; A. Salemnia; M. R. Aghamohammadi
Abstract
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 ...
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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.
Power System Stability
M. Abbasi; B. Tousi
Abstract
In this paper, dynamic performance of a transformerless cascaded PWM static synchronous shunt compensator (STATCOM) based on a novel control scheme is investigated for bus voltage regulation in a 6.6kV distribution system. The transformerless STATCOM consists of a thirteen-level cascaded H-bridge inverter, ...
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In this paper, dynamic performance of a transformerless cascaded PWM static synchronous shunt compensator (STATCOM) based on a novel control scheme is investigated for bus voltage regulation in a 6.6kV distribution system. The transformerless STATCOM consists of a thirteen-level cascaded H-bridge inverter, in which each voltage source H-bridge inverter should be equipped with a floating and isolated capacitor without any power source. The proposed control algorithm uses instantaneous p-q power theory in an innovative way that devotes itself not only to meet the reactive power demand but also to balance the dc link voltages at the same time. DC link voltage balancing control consists of two main parts: cluster and individual balancing. The control algorithm based on a phase shifted carrier modulation strategy has no restriction on the number of cascaded voltage source H-bridge inverters. Comprehensive simulations are presented in MATLAB/ SIMULINK environment for validating the performance of proposed transformerless STATCOM.
M. Karimi; M. Eslamian
Abstract
This paper presents a resilience-based approach for critical load restoration in distribution networks using microgrids during extreme events when the main supply is disrupted. Reconfiguration of the distribution network using graph theory is investigated, for which Dijkstra's algorithm is first used ...
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This paper presents a resilience-based approach for critical load restoration in distribution networks using microgrids during extreme events when the main supply is disrupted. Reconfiguration of the distribution network using graph theory is investigated, for which Dijkstra's algorithm is first used to determine the shortest paths between microgrids and critical loads, and then the feasible restoration trees are established by combining the restorable paths. A mixed-integer linear programming (MILP) model is then used to find the optimal selection of feasible restoration trees to make a restoration scheme. The service restoration is implemented with the objectives of maximizing the energy delivered to the critical loads and minimizing the number of switching operations. The limited fuel storage of the generation sources in microgrids, the operational constraints of the network and microgrids, as well as the radiality constraint of the restored sub-networks, are considered the constraints of the optimization problem. The presented method can be used for optimal restoration of critical loads including the number of switching operations which is essential for the ease of implementation of a restoration plan. The results of simulations on a 118-bus distribution network demonstrate the efficiency of the procedure.
M.H. Amirioun; E. Heydarian-Forushani
Abstract
With the advent of advanced measurement and supervisory devices in power systems, wide area measurement systems and real-time monitoring of power systems have become viable. Accordingly, modeling techniques should be updated as well. This paper proposes a transformer asset management model based on real-time ...
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With the advent of advanced measurement and supervisory devices in power systems, wide area measurement systems and real-time monitoring of power systems have become viable. Accordingly, modeling techniques should be updated as well. This paper proposes a transformer asset management model based on real-time condition monitoring in the presence of distributed generation. The model is tested under different case studies and compared with the previous models in which constant failure rate model was used for asset management of transformers. The system cost includes operation, repair, and interruption costs. The objective is to determine the hourly loading of the transformer so that the cost of system is minimized. The long-term objective is to determine the loading pattern of the transformer which guaranties the most economical pattern among various options. Results showed that the proposed model is efficiently capable of returning more accurate responses if real-time monitoring data is used. A set of sensitivity analysis studies are also performed to highlight the impact of each factor separately. The contribution of distributed generators to supply the load is also investigated. Results showed that the use of distributed generators reduces the overall cost of the system by diminishing the risk-based element of the system cost.
Power Electronic
E. Seifi Najmi; A. Ajami; A. H. Rajaei
Abstract
This paper proposes a novel topology of multilevel current source inverter which is suitable to apply in low/medium voltage. The proposed topology is capable of producing desirable bidirectional output current levels. Furthermore, it can employ symmetrical DC current sources as well as asymmetrical ones ...
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This paper proposes a novel topology of multilevel current source inverter which is suitable to apply in low/medium voltage. The proposed topology is capable of producing desirable bidirectional output current levels. Furthermore, it can employ symmetrical DC current sources as well as asymmetrical ones which is a significant advantage. Asymmetrical mode makes it possible to generate a great number of output levels by appropriate selection of DC current source magnitude, needless to make changes in the hardware of the inverter. As a result, various methods are presented to compute the magnitude of needed DC current sources. In comparison to the conventional H-Bridge inverter (CHB), the proposed inverter has lessened the number of required DC current sources, switches as well as related gate driver circuits. The reduced number of required components has leads to cost and volume advantages. In addition, the control layout has become simpler. Reduction of power loss as a result of reduced number of on-state switches is the other merit of the proposed inverter. To evaluate the efficiency of the proposed inverter, its simulation and experimental results are extracted including results of various methods of determining DC current source magnitude.
Distribution Systems
M. Alilou; D. Nazarpour; H. Shayeghi
Abstract
The optimal management of distributed generation (DG) enhances the efficiency of the distribution system; On the other hand, increasing the interest of customers in optimizing their consumption improves the performance of DG. This act is called demand side management. In this study, a new method based ...
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The optimal management of distributed generation (DG) enhances the efficiency of the distribution system; On the other hand, increasing the interest of customers in optimizing their consumption improves the performance of DG. This act is called demand side management. In this study, a new method based on the intelligent algorithm is proposed to optimal operate the demand side management in the presence of DG units and demand response. Firstly, the best location and capacity of different technologies of DG are selected by optimizing the technical index including the active and reactive loss and the voltage profile. Secondly, the daily performance of multi-DG and grid is optimized with and without considering the demand response. The economic and environmental indices are optimized in this step. In both steps, the non-dominated sorting firefly algorithm is utilized to multi-objective optimize the objective functions and then the fuzzy decision-making method is used to select the best result from the Pareto optimal solutions. Finally, the proposed method is implemented on the IEEE 33-bus distribution system and actual 101-bus distribution systems in Khoy-Iran. The obtained numerical results indicate the impact of the proposed method on improving the technical, economic and environmental indices of the distribution system.
M.S. Syed; C.V. Suresh; S. Sivanagaraju
Abstract
In this paper, Renewable energy sources (RES) are incorporated into the electricity grid. A real-time Andhra Pradesh 14 bus system is considered in which, windy and sunny locations are identified for this study. A new algorithm called Persistence - Extreme Learning Machine (P-ELM) is suggested. The suggested ...
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In this paper, Renewable energy sources (RES) are incorporated into the electricity grid. A real-time Andhra Pradesh 14 bus system is considered in which, windy and sunny locations are identified for this study. A new algorithm called Persistence - Extreme Learning Machine (P-ELM) is suggested. The suggested methodology is used to predict wind speed and solar insolation in the selected regions across the short-term and long-term time period horizons. The load flow problem is handled in 12 distinct by penetrating the wind and solar power into the system. The research findings are examined in terms of voltage variation and active power loss. The results obtained observed as, with wind and solar integration, the voltage variation is higher in both the short and long-term time frames, but the active power losses are lower than in the other cases.
