Amir Hassan Shams-Ansari ¹, Farzad Razavi ¹, Ali Asghar Ghadimi ², Hossein Abolmasoumi ³

Affiliations
1 Department of Electrical Engineering, University of Tafresh, Tafresh, IR
2 Department of Electrical Engineering, Science and research branch, Islamic Azad University, Arak, IR
3 Department of Electrical Engineering, Arak University, Arak, IR

Abstract

Converters are widely used in many fields specially Distributed Generation applications. Because of the non-linear and the uncertain characteristics of DC-DC converters, Sliding Mode Control (SMC), which is robust against uncertainties and disturbances, is implemented in a full-bridge converter in order to control the converter output by varying the duty cycle of the converter. The proposed method is explained and formulated using state-space average model of the fullbridge converter. Additionally, the effects of changing the design parameters of the introduced sliding mode controller in tracking performance and tracking are discussed. Moreover, the system behavior during load and source sudden changes is analyzed. High performance and tracking accuracy of the system under parameter variation are confirmed appropriately using simulations.

Keywords

Full-Bridge Converter, Sliding Mode Control, Nonlinear Control, DG

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Peyman Salah ¹, Seyed Siavash Karimi Madahi ¹, Hassan Feshki Farahani ², Ali Asghar Ghadimi ³

Affiliations
1 Department of Electrical Engineering, Abhar Branch, Islamic Azad University, Abhar, IR
2 Department of Electrical Engineering, Ashtian Branch, Islamic Azad University, Ashtian, IR
3 Department of Electrical Engineering, Science and Research Branch, Islamic Azad University, Arak, IR

Abstract

One of the most important issues in modeling and simulation of electricity distribution systems is to know different customers' consumption, which depends on season, weekdays and hour day. So, load behavior pattern and determination of its value is of great importance. In this paper, a method is proposed to measure substation values using registers. Then, the method to obtain consumption pattern curve is presented. After that, a strategy is discussed to determine the peak and minimum values of load curve using normalized energy value consumed by customers. This method is implemented on a sample distribution system of Ashtian town in Iran. Obtained results verify the capability of the method to estimate load consumption value in each hour of a day.

Keywords

Computer Modeling, Consumption Demand, Consumption Pattern, Distribution Systems, Load Duration Curve

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Hamidreza Mahdian , Mohamadreza Hashemi , Ali Asghar Ghadimi

Abstract

Phase-Locked Loop (PLL) Structures have many applications in power system engineering. When required the synchronous performance of Voltage Sourced Converter (VSC) with Grid, such as wind power generation system, active filters, HVDC transmission lines and FACTS devices, the most common method for accurate estimation of frequency of network, is to use a PLL. However, problems such as grid disturbances due to noise, voltage unbalances, lack of coordination, changes in grid frequency and harmonics can produce a frequency disturbance, twice the grid frequency and disturbed PLL and also the control system connected to it. In this paper, common structures of PLL is introduced. After that, unbalance and disturbance in the three phase input of PLL is studied. Then for idea and invention in PLL, a new control method based on predictive control technique is used in the control strategy of converter. Furthermore, the use of type III controller in PLL to ensure optimal performance in various conditions is proposed in this paper. How to set the parameters of the proposed controller is described by the Bode stability criterion. Conducting simulations to evaluate the performance of the proposed method is done in PSIM software. According to the proposed method and the result observed, the double frequency disturbance term is weakened and also the transient state is improved.

Keywords

Phase-Locked Loop (PLL), Voltage-Sourced Converters (VSC), Synchronization, Current Control, Unbalanced Voltage

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Mohamadreza Hashemi ¹, Hamidreza Mahdian ¹, Ali Asghar Ghadimi ²

Affiliations
1 Department of Electrical Engineering, Science and Research Branch, Islamic Azad University, Arak, IR
2 Department of Electrical Engineering, Faculty of Engineering, Arak University, Arak, IR

Abstract

One of the facing problems in distributed generation is being unintentionally islanded which the detection of this phenomenon is of great importance. Common methods are active and passive islanding detection. These two methods are based on changing in parameters such as frequency, voltage and current harmonics. If, after the islanding occur, this changes are revealing and visible, islanding phenomenon is demonstrated which is detected by passive methods. If the generated power of inverter is equal to local loads consumption and assuming of the generated reactive power of grid connected inverter equal to zero, it should be detected by active methods but these two methods have some challenges such as reduction in power quality or wide Non Detection Zone (NDZ). In this paper, in proposed method, change of a new parameter will be studied for islanding detection diagnosis. With the difference that the studied system is a three phase system and unbalanced load is studied which is more consistent to reality. Because of small changes in parameters, we have to find the right approach toward active methods. Generally there are two views about the islanding performance. At first view, this phenomenon is seems negatively but in fact this is an opportunity. The first view suggests that all generators in the island should bring out of grid within a maximum of two seconds. In this view the concept of anti-islanding protection is proposed to tackle the task of creating such islands. The second view expresses the concept of micro grid. In this case as far as possible, power required by Inner Island loads were provided by distributed generators. The studied system was similar to standard IEEE-1547 and UL-1741. With the difference that we used three phase and local loads are assumed unbalanced. Conventional active detection methods are not able to identify the island with the aim to help keep it stable. They usually try to bring out the electrical parameters such as voltage and frequency from nominal limits. So in micro grids the island should be diagnosed using passive or remote techniques. Note that detection time of 2 seconds which is referred to on standards is not good and the detection time must be lower than this value. However, the proposed method that is one of the active detection methods is capable for use in micro grids. Simulation results using PSIM software on standard network shows the effectiveness of the proposed method.

Keywords

Islanding, Unbalanced Loads, dq-frame, Phase Locked Loop (PLL), Non Detection Zone (NDZ), Micro-grid

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Masoud Ghazipour Shirvan ¹, Ali Asghar Ghadimi ²

Affiliations
1 Department of Electrical Engineering, Science and Research Branch, Islamic Azad University, Arak, IR
2 Department of Electrical Engineering, Arak University, Arak, IR

Abstract

This paper deals with the selection type and capacity of hybrid DGs in a stand–alone distribution system considering random behavior of loads and generators in augmenting renewable energy sources. Two methods were used to determine the capacity: by using Deterministic Parameters irrespective of stochastic behavior of loads and generators; the other was by considering the random behavior of renewable energies and loads. The objective is to minimize the cost and reliability constraint problem. In fact, the problem of capacity determination is expressed as a non-linear optimization problem. The combination of considered DG is wind, solar and battery that is independent from the network. The capacity was determined with respect to random behavior of DG and load. We used the Probability Density Function for DG and sequence Monte Carlo Method for load determination. Intelligent Algorithm (PSO) was used to find out the optimal capacity of DGs. All of the simulations were made in MATLAB software.

Keywords

Wind Energy, Solar Energy, Battery, Monte Carlo, Algorithm of Particle Mass

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Mohammad Mohammadinodoushan ¹, Ali Asghar Ghadimi ², Abolfazl Salami ³, Hamid Reza Alirezaei ¹, Alireza Mohammadi-Nodooshan ⁴

Affiliations
1 Electrical Engineering Department, Science and Research Branch, Islamic Azad University, Tehran, IR
2 Electrical Engineering Department, Arak University, Arak, IR
3 Electrical Engineering Department, Arak University of Technology, Arak, IR
4 Department of Electrical Engineering, Science and Research Branch, Islamic Azad University, Tehran, IR

Abstract

Background/Objectives: Several advantages of Distributed Generation (DG) have created incentives to increase DG penetration in distribution networks. In order to meet this requirement, Coordinated Reconfiguration and Voltage Control (CRVC) is used in this paper. Methods: To do so, simulations are done in two parts. In the first part, the power loss of a distribution system is decreased through CRVC, and in the second part, DG allowable capacity is increased through CRVC. In order to decrease the computational time for finding the best network configuration and voltage control devices values, modified Binary Particle Swarm Optimization (BPSO) is used. The method has been tested on a 33-bus radial distribution system. Findings and Improvements: Simulation results in both two parts show the efficiency of the method. In the first part, CRVC method could decrease power loss 33%. In the second part, the DG allowable penetration is increased 140% thorough CRVC. This shows that this method is more robust than various techniques that have been proposed to increase DG allowable capacity in the past. Moreover, without using complex voltage control methods, CRVC improved the voltage of all busses considerably. Furthermore, simulations verified the decrease in computational time for reconfiguration which is an important challenge in using reconfiguration.

Keywords

Binary Partcile Swarm Optimization, Distributed Generation, Loss Reduction, Reconfiguration, Voltage Control

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