Sharif Digital Repository

This paper discusses various aspects of unified power flow controller (UPFC) control modes and settings and evaluates their impacts on the power system reliability. UPFC is the most versatile flexible ac transmission system device ever applied to improve the power system operation and delivery. It can control various power system parameters, such as bus voltages and line flows. The impact of UPFC control modes and settings on the power system reliability has not been addressed sufficiently yet. A power injection model is used to represent UPFC and a comprehensive method is proposed to select the optimal UPFC control mode and settings. The proposed method applies the results of a contingency... 

This paper presents a robust decentralized proportional-integral (PI) control design as a solution of the load frequency control (LFC) in a multi-area power system. In the proposed methodology, the system robustness margin and transient performance are optimized simultaneously to achieve the optimum PI controller parameters. The Kharitonov's theorem is used to determine the robustness margin, i.e., the maximal uncertainty bounds under which the stable performance of the power system is guaranteed. The integral time square error (ITSE) is applied to quantify the transient performance of the LFC system. In order to tune the PI gains, the control objective function is optimized using the... 

A fractional order PID controller is designed to stabilize fractional delay systems with commensurate orders and multiple commensurate delays, where the time delays in the system may belong to several distinct intervals. Moreover, the controller parameters should belong to given intervals. In order to stabilize the system, the D-subdivision method is employed to choose the stabilizing set of the controller parameters from their available values. Furthermore, the nearest values of the obtained stabilizing set to their mean values are selected as the controller parameters so that a non-fragile controller is concluded. Two numerical examples evaluate the proposed control design method  

This paper presents closed loop simulation of a CMOS-MEMS force sensor for biomedical applications employing an optimal proportional-integral-derivative controller. Since the dynamic behavior of the sensor under investigation is nonlinear the iterative feedback tuning approach was proposed for optimal gains tuning of the proposed controller. Simulation results presented in this research illustrate that the proposed controller suppresses the undesired in-plane vibration induced by environment or gripper 40 times faster than the nonlinear controller proposed in the literature. To suppress the maximum input disturbance the maximum voltage was approximately 18 V which was less than the pull-in... 

Objective: The objective of this paper is to develop a hierarchical two-level power system load frequency control. Design: At the button level, standard PI controllers are utilized to control area's frequency and tie-line power interchanges. At the higher layer, model predictive control (MPC) is employed as a supervisory controller to determine the optimal set-point for the PI controllers in the lower layer. The proposed supervisory predictive controller computes the optimal set-points such that to coordinate decentralized local controllers. Blocking and coincidence point technology is employed to alleviate the computational effort of the MPC. In order to achieve the best closed loop... 

Available transfer capability (ATC) is a measure of the transfer capability remaining in a transmission system. Application of unified power flow controllers (UPFCs) could have positive impacts on the ATC of some paths while it might have a negative impact on the ATC of other paths. This paper presents an approach to evaluate the impacts of UPFCs on the ATC from a cost/worth point of view. The UPFC application worth is considered as the maximum cost saving in enhancing the ATC of the paths due to the UPFC implementation. The cost saving is considered as the cost of optimal application of other system reinforcement alternatives (except for UPFC) to reach the same ATC level obtained by UPFC... 

Utilization of Unified Power Flow Controllers (UPFCs) can be more beneficial in the restructured power systems due to their capabilities in increasing the transmission line capacities as well as shunt reactive compensation. So, these devices should be installed such that the most benefit can be gained. In this paper, the problem of optimal placement of UPFCs is solved using Mixed-Integer Non-Linear Programming (MINLP) method. Hence, the problem is completely formulated based on this method and is solved using available commercial solvers. The salient feature of this method is having potential to simultaneously determine the optimal location of multi UPFCs. Also, since a full AC Optimal Power... 

Application of fractional order PID (FOPID) controller to an automatic voltage regulator (AVR) is presented and studied in this paper. An FOPID is a PID whose derivative and integral orders are fractional numbers rather than integers. Design stage of such a controller consists of determining five parameters. This paper employs particle swarm optimization (PSO) algorithm to carry out the aforementioned design procedure. PSO is an advanced search procedure that has proved to have very high efficiency. A novel cost function is defined to facilitate the control strategy over both the time-domain and the frequency-domain specifications. Comparisons are made with a PID controller and it is shown... 

In this paper, AC Optimal Power Flow combined with UPFC has been used to manage the congestion of transmission lines in a restructured power system with pool market model. The modeling of Unified Power Flow Controller (UPFC) has been adopted based on bipolar model and power injection method. To determine an appropriate location for UPFC as well as to set its parameters, an approach based on genetic algorithm has been suggested. The modified IEEE 14-bus system is used to determine the effectiveness and applicability of the proposed method and results are discussed. ©2006 IEEE  

This paper presents a single-phase phase-locked loop (PLL) system which is primarily free from the double-frequency ripples from which the conventional PLL system suffers. The proposed PLL is then extended to reject the harmonic components from the input signal and to estimate the phase-angle and frequency of the distorted input signal with no error. Three units of the proposed PLL can be used in three-phase power systems, such as FACTS and HVDC converters, to estimate the phase-angles of the individual phases with no double-frequency ripples and without sensitivity to the presence of harmonics and inter-harmonics. This makes the proposed PLL unique and desirable for applications which... 

Fractional order PID controllers are suitable for almost all types of dynamic models. In this paper, a new adaptive fractional order PID controller using neural networks is introduced.The overall performance using the proposed adaptive fractional order PID controller is demonstrated through some examples. It is shown that the new controller scheme can give excellent performance and more robustness in comparison with the conventional controllers like GPC  

This paper evaluates the reliability impact of UPFC application in power system. The paper proposes a new reliability model for the UPFC which is capable of considering different operating states of UPFC. The model is then applied to a test system to study the reliability impacts of UPFC. The impacts of operating points of different states of the model on the system reliability are analyzed. The role of model parameters in reliability impacts of UPFC is analyzed through the sensitivity analysis. A comparative study is finally conducted to illustrate the applicability of the proposed model compare to that of existing UPFC reliability models. The abilities and deficiencies of the proposed... 

this paper presents two new methods for power flow calculation of power systems in presence of Dynamic Flow Controller (DFC), which is a new member of FACTS controllers. In first method A new steady state model of DFC is introduced for the implementation of the device in the conventional Newton-Raphson power flow algorithm. The impact of DFC on power flow is accommodated by adding new entries and modifying some existing ones in the linearized Jacobian equations of the same system without DFC. The focus of second method is on the discrete nature of the DFC and including its effects on power flow. This method is based on Nabavi model for FACTS devices. A case study on a power system located in... 

This paper probes the impact of utilizing an IPFC on the reliability indices of interconnected power systems. First, a concise presentation of IPFC and its structure are provided and the reliability model of two unequally-rated parallel transmission lines equipped with IPFC is then extracted. The assumed IPFC is composed from two parallel converting bridges associated with each line. Afterwards, based-on equivalent assisting unit approach, different commonly-used adequacy indices including the loss of load expectation (LOLE), loss of energy expectation (LOEE) and system minutes (SM) are calculated. A set of numerical analyses are conducted to illustrate the sensitivity of these indices with... 

In this paper we propose to control a bipedal robot in an unstable position by means of a PID controller that gains are turned by a fuzzy logic system. For that, a model of planar 3 linked segment consisting of limb, trunk and extended arms with fixed base is used. Fuzzy if-then rules are constructed based on human expert knowledge and biomechanics studies for tuning of PID's gain. For construction of tuning rules, we have developed an optical measuring system to record experimental data of balance keeping of a human in an unstable position. The control model is based on three sets of different global variables: (1) limb orientation and its derivative, (2) trunk/upper attitude and its... 

This paper proposes a novel method to designing an H∞ PID controller with robust stability and disturbance attenuation. This method uses particle swarm optimization algorithm to minimize a cost function subject to-norm to design robust performance PID controller. We propose two cost functions to design of a multiple-input, multiple-output (MIMO) and single-input, single-output (SISO) robust performance PID controller. We apply this method to a SISO flexible-link manipulator and a MIMO super maneuverable F18/HARV fighter aircraft system as two challenging examples to illustrate the design procedure and to verify performance of the proposed PID controller design methodology. It is shown with... 

The significant importance of micro-scaled devices in medicine, lab-on-a-chip, and etc resulted in a vast variety of researches. The idea behind the novel hydro magnetic micro-pump and flow controller is that ferromagnetic particles, mixed and dispersed in a carrier fluid, can be accumulated and retained at specific sites to form pistons in a micro-tube using some external magnetic field sources along the micro-tube. This external magnetic field is related to some solenoids, which are turned on and off alternatively. Depending upon dragging speed of these pistons, which itself is a function of switching time, this device can be used to either increase (pumping) or decrease (valving) the flow... 

The novel idea of the Hydromagnetic Micropump and Flow Controller (HMFC) is used in this paper to construct a laboratory setup capable of bidirectional pumping and controlling the flow in microtubes. A laboratory setup, which contains no moving parts, is integrated with a pressure-driven flow setup to make the presented HMFC device. The device operation is based on controllable motion of magnetic particles, added to the carrier fluid, caused by the magnetic field, produced by solenoids located just next to the microtube. The magnitude of these forces is proportional to the strength and gradient of magnetic field which, in turn, is related to the electrical current and arrangement of the... 

Inverse dynamics analysis as well as the generation of an optimal goal oriented human motion both lead to the problem of finding suitable activations of the redundant muscles involved. This paper employs an iterative feedback tuning approach to perform the forward dynamics simulation of the human musculoskeletal system during level walking. A modified form of the proportional-integral-derivative (PID) controller is proposed to stabilize the movement and provide tracking of problems of the desired lower extremity joint profiles. Controller parameters were determined iteratively using an optimization algorithm to minimize tracking errors during forward dynamics simulation. Static optimization... 

This paper discusses various aspects of unified power flow controller (UPFC) control modes and settings and evaluates their impacts on the power system reliability. UPFC is the most versatile flexible ac transmission system device ever applied to improve the power system operation and delivery. It can control various power system parameters, such as bus voltages and line flows. The impact of UPFC control modes and settings on the power system reliability has not been addressed sufficiently yet. A power injection model is used to represent UPFC and a comprehensive method is proposed to select the optimal UPFC control mode and settings. The proposed method applies the results of a contingency...