Mehrdad Tarafdar Hagh | University of Tabriz (original) (raw)

Papers by Mehrdad Tarafdar Hagh

This paper presents a Least Absolute Value (LAV) state estimator for power system using a new me... more This paper presents a Least Absolute Value (LAV) state estimator for power system using a new method called Recursive Least Squares (RLS). Also, a suitable model is used for state estimation of power system that includes a Unified Power Flow Controller (UPFC). The IEEE 14-bus test system is used to show the validity of the proposed algorithm in estimation of power system states as well as the states of controllable parameters of UPFC.

Minimization of load shedding during contingency conditions is solved as an optimization problem.... more Minimization of load shedding during contingency conditions is solved as an optimization problem. As a new topic, instead of local load shedding, total load shedding of a large power system is considered. Power generation rescheduling is considered to minimize the load shedding, as well. Different importance factors for buses are also considered. The linear programming method (LP) is used to solve this problem in a short period of time without considering some power system constraints. Particle swarm optimization (PSO) is also used
to solve the problem by considering all power system constraints, but with a longer solving time. Finally, a new method, the sequential use of LP and PSO, is proposed, which is faster than PSO and considers all constraints. The IEEE 14 bus test system is used to compare the performance of the mentioned methods and a comparison of the proposed algorithm and genetic algorithm is accomplished.

In this paper a novel configuration of unified power flow controller (UPFC) which consists of two... more In this paper a novel configuration of unified power flow controller (UPFC) which consists of two shunt converters and a series capacitor is proposed. In this configuration, a series capacitor is used between two shunt converters to inject desired series voltage. As a result, it is possible to control the active and reactive power flow as same as the conventional configuration of UPFC. The main advantage of the proposed
UPFC in comparison with the conventional configuration is injection of a series voltage waveform with a very low total harmonic distortion (THD). Also, using two shunt converters instead of a series and a shunt converters, results in reduction of design efforts and simplification of control, measuring and
protection strategies. An optimal control strategy based on the discrete model of converters is applied to shunt converters. The proposed UPFC is simulated using PSCAD/EMTDC and MATLAB software and simulation results are presented to validate the effectiveness of the novel configuration of UPFC. Also, the experimental results which are obtained from an experimental set-up are presented.

In this paper, voltage sag compensation of point of common coupling (PCC) using a new structure o... more In this paper, voltage sag compensation of point of common coupling (PCC) using a new structure of fault current limiter (FCL) is proposed. The proposed structure prevents voltage sag and phase-angle jump of the substation PCC after fault occurrence. This structure has a simple control method. Using the semiconductor switch (insulated-gate bipolar transistor or gate turnoff thyristor at dc current rout leads to fast operation of the proposed FCL and, consequently, dc reactor value is reduced. On the other hand, the proposed structure reduces the total harmonic distortion on load voltage and it has low ac losses in normal operation. As a result, other feeders, which are connected to the substation PCC, will have good power quality. Analytical analysis and simulation results using PSCAD/EMTDC software and experimental results are presented to validate the effectiveness of this structure.

This paper presents a novel solution based on the group search optimizer (GSO) methodology in ord... more This paper presents a novel solution based on the group search optimizer (GSO) methodology in order to determine the feasible optimal solution of the economic dispatch (ED) problem considering valve loading effects. The basic disadvantage of the original GSO algorithm is the fact that it gives a near optimal solution rather than an optimal one in a limited runtime period. In this paper, a new modified
group search optimizer (MGSO) is presented for improving the scrounger and ranger operators of GSO. The proposed MGSO is applied on different test systems and compared with most of the recent methodologies. The results show the effectiveness of the proposed method and prove that MGSO can be applicable for solving the power system economic load dispatch problem, especially in large scale power systems.

Conventional distance protection applies the positive- sequence impedance to protect a line again... more Conventional distance protection applies the positive-
sequence impedance to protect a line against short-circuit
faults. Series-compensated lines may considerably change the
positive-sequence impedance of the fault path and cause the
distance relays to maloperate. To overcome this problem, the
mutual impedance between phases of a transmission line is used for the design of a new distance protection scheme. The voltages and currents of both ends of the line are applied to compute the mutual impedance between the relay and the fault point. The proposed scheme has a reliable performance in protection against single-phase and double-phase-to-ground faults and, therefore, it can be used as a backup protection. Simulation results approve the efficiency of the proposed method in protection of series-compensated transmission lines.

In this paper, a new protection scheme for transmission lines is presented. The method has some a... more In this paper, a new protection scheme for transmission
lines is presented. The method has some advantages in comparison with conventional line protection schemes. Faster fault detection and instantaneous coverage of almost 100% of the line are the main advantages of the new method. A full-cycle averaging window is used for fault detection. While the power system is in normal operation conditions, this average is approximately equal to zero. As soon as the faulty signals enter the window, the average is changed to a nonzero value. It is shown that the product of this average value for voltage and current of the faulty phase, in a specific time interval after fault inception, is negative for the forward faults and positive for the reverse faults. The fault is detected by communication between the local and the remote relays. Simulation and experimental results show the efficiency of the proposed method in fast detection of line faults in less than a half cycle.

This paper presents a new methodology to estimate harmonic distortion in a distribution system, b... more This paper presents a new methodology to estimate harmonic distortion in a distribution system, based on measurements of a limited number of given buses. The algorithm utilizes Principal Component Analysis (PCA). First the PCA of buses is detected off-line from their historical data. Next, the interrelations between the voltages are developed using Inverse PCA method. Finally, through incorporation of a certain finite set of real-time data measurements, the voltages of all network buses in real-time are estimated with a desired
degree of accuracy via the Inverse PCA method (IPCA). The algorithm is applied to an existing industrial distribution network as a test case. This case study shows good agreement between proposed methods with on site measurements.

The performance of the state estimation (SE) depends on the accuracy of the received measured dat... more The performance of the state estimation (SE) depends on the accuracy of the received measured data, as well as the parameter data of the power system. In this paper, a new algorithm is proposed for the simultaneous identification and correction of measurement and branch parameter errors (series and shunt admittances) in the power system SE problem. The proposed method uses Lagrange multipliers for the identification and correction of branch parameter errors without the need for a-priori specification of suspect parameter vectors. Erroneous measurements
and branch parameter values can be corrected using the proposed method to estimate the measurement and branch
parameter errors. Finally, IEEE 14-, 30-, and 57-bus test systems are used to show the validity and robustness of the
proposed algorithm. Single, multiple, and simultaneous errors in the conventional measurements and branch parameters
are considered for different case studies.

In power systems with the high penetration of renewable energies such as wind powers, accuracy in... more In power systems with the high penetration of renewable energies such as wind powers, accuracy in predicting power system state is really important, especially in bidding strategies, risk management and operational decisions. In this paper, the impact of STATic COMpensator (STATCOM) and Static Series Synchronous Compensator (SSSC) on predictability of power system is studied. For this investigation, predictability
indices are utilized. This paper clarifies some important questions and concerns about power system such as; do the STATCOM and SSSC improve or impair the predictability of system state? Also, this paper warns the operator of system about ignoring the predictability concept in FACTS included power systems. Moreover, the necessity of utilizing predictability indices in optimization problems beside conventional objectives, such as losses, is discussed. The results are discussed on IEEE 14 and 57 bus test systems.

In this paper a new power circuit topology for FACTS controllers is introduced. This topology is ... more In this paper a new power circuit topology for FACTS controllers is introduced. This topology is neither series nor parallel FACTS controller. This controller injects an additive compensating voltage between each of two phases of a three phase power line by using a voltage source inverter (VSI). So, it is named as line to line compensator (LLC). Analytical analysis and simulation results by MATLAB/SIMULINK are presented and a test setup is built to verify the operation of proposed FACTC controller.

In this paper, the elimination of harmonics in a cascade multilevel inverter by considering the n... more In this paper, the elimination of harmonics in a cascade multilevel inverter by considering the nonequality of
separated dc sources by using particle swarm optimization is
presented. Solving a nonlinear transcendental equation set
describing the harmonic-elimination problem with nonequal dc
sources reaches the limitation of contemporary computer algebra software tools using the resultant method. The proposed approach in this paper can be applied to solve the problem in a simpler manner, even when the number of switching angles is increased and the determination of these angles using the resultant theory approach is not possible. Theoretical results are verified by experiments and simulations for an 11-level H-bridge inverter. Results show that the proposed method does effectively eliminate a great number of specific harmonics, and the output voltage is resulted in low total harmonic distortion.

In this paper, the results of providing and implementation of the state estimation (SE) program a... more In this paper, the results of providing and implementation of the state estimation (SE) program and
also input/output required information has been presented for the first time in North-West dispatching center of
the country. The SE program has been written based on weighted least square (WLS) in the MATLAB software
and is able to estimate amplitudes and phase angles of all 132kV, 230kV and 400kV power stations voltages in
North-West region of country, every instant. Moreover, in order to convert the measured information and
identify the close/open status of the power stations circuit breakers, a special program was written in the C++
software. This program delivers the mentioned information in a desired order to the SE program, in each
program execution cycle. Output of the proposed SE program provides two options for the experts and
operators of the dispatching center. In the first option, output of SE program can be used in the form of a special
monitoring system unsig Bitmap figures without using any other programs. While for the second option, SE
program output is imported to the well-known DIgSILENT software using a special input script data file, which
can be presented with the DIgSILENT software and used for the other of power network calculations.

This paper proposes a new parallel-LC-resonance type fault current limiter (FCL) that uses a resi... more This paper proposes a new parallel-LC-resonance type
fault current limiter (FCL) that uses a resistor in series with
a capacitor. The proposed FCL is capable of limiting the fault
current magnitude near to the prefault magnitude of distribution feeder current by placing the mentioned resistor in the structure of the FCL. In this way, the voltage of the point of common coupling does not experience considerable sag during the fault.
In addition, the proposed FCL does not use a superconducting
inductor which has high construction cost. Analytical analysis for this structure is presented in detail, and simulation results using power system computer-aided design/electromagnetic transients, including dc software are obtained to validate the effectiveness of this structure. Also, an experimental setup is provided to show the accuracy of the analytic analyses and simulation results.

Accurate prediction of power system state has significant importance specially in bidding strateg... more Accurate prediction of power system state has significant importance specially in bidding strategies, risk management
and operational decisions. Consideration of this matter is very important, especially in systems with large penetration of
renewable energies such as wind powers. The effect of the most versatile flexible alternative current transmission systems
(FACTS) devices unified power flow controller (UPFC) on predictability of power system state has been studied. For this
purpose, predictability indices are used which can quantify the ability of system prediction. The likely harmful properties of
UPFC in power system predictability are presented and the results are discussed on IEEE 14 and IEEE 57 bus test system.

This paper presents an improved heuristic algorithm for solving combined heat and power economic ... more This paper presents an improved heuristic algorithm for solving combined heat and power economic dispatch
(CHPED) problem in large scale power systems, by employing improved group search optimization
(IGSO) method. The basic deficiency of the original GSO algorithm is the fact that, it gives a near optimal
solution rather than an optimal one in a limited runtime period. In this paper, some modifications have
been applied to the original GSO in order to improve its searching ability. In this work, a sinusoidal term
is employed to consider the valve-point effects and Kron’s formula is used in order to consider the transmission
losses. Moreover, prohibited operating zones of power-only units are considered. The effectiveness
and accuracy of the proposed method for solving the non-linear and non-convex problems is
validated by carrying out simulation studies on sample benchmark test cases and three large scale power
systems. Numerical results indicate that proposed method has the better performance in comparison
with original GSO and some recently published papers.

This paper presents a novel method to solve security based optimal placement and parameter settin... more This paper presents a novel method to solve security based optimal placement and parameter setting of
unified power flow controller (UPFC) problem based on hybrid group search optimization (HGSO)
technique. Firstly, HGSO is introduced in order to solve mix-integer type problems. Afterwards, the proposed
method is applied to the security based optimal placement and parameter setting of UPFC problem.
The focus of the paper is to enhance the power system security through eliminating or minimizing the
over loaded lines and the bus voltage limit violations under single line contingencies. Simulation studies
are carried out on the IEEE 6-bus, IEEE 14-bus and IEEE 30-bus systems in order to verify the accuracy and
robustness of the proposed method. The results indicate that by using the proposed method, the power
system remains secure under single line contingencies.

This paper presents a new multi-stage model, based on the mixed integer nonlinear programming (MI... more This paper presents a new multi-stage model, based on the mixed integer nonlinear programming (MINLP)
approach, to determine the optimal sub-transmission system expansion planning (SSEP). This model
considers the placement of distributed generation (DG) units in distribution networks over the planning
periods. The SSEP determines the facilities which should be installed and/or reinforced so that the system
serves the forecasted demand at the lowest cost while satisfying the operational constraints. These constraints
include the maximum allowable voltage drop, and the operation capacity of substations, MV
feeders, and DG units. Meanwhile, the proposed model presents the optimal planning of existing and
new sub-transmission substations, as well as the routes of medium voltage (MV) feeders. Moreover,
the allocation and operation planning of DG units over the planning period is considered, as well. On
the other hand, the expanding limitations of existing and candidate sub-transmission substations and
DG units are considered as the expansion constraints in the SSEP problem. The effectiveness of proposed
MINLP-based model is demonstrated using several case studies.

Lancet

This paper presents a new method for minimizing the number of PMUs and their optimal placement in... more This paper presents a new method for minimizing the number of PMUs and their optimal placement in power systems. The proposed method provides suitable constraints for power systems with two adjacent injection measurements (IMs). In addition, suitable constraints for considering the connection of two buses to each other and to an injection bus are proposed. The proposed constraints result in a reduction in the number of PMUs even though the system topological observability is complete. Existing conventional measurements are also considered. First, the number of PMUs is minimized in such a way that the system topological observability is complete. Then the optimal placement is done to maximize the measurements redundancy. The resulting phased to be installed in multiple stages. The optimal number of PMUs that ensure system topological observability under failure of a PMU or a line is also simulated. Simulations are performed on IEEE 30, 57 and 118 bus test systems by binary integer programming. The results show that the number of PMUs is equal to or less than the corresponding results of recently published papers, while the system topological observability is complete, and measurement redundancy is increased. (S.M. Mahaei), tarafdar@tabrizu.ac.ir (M.T. Hagh).

IEEE Transactions on Industrial Electronics, 2010

In this paper, the elimination of harmonics in a cascade multilevel inverter by considering the n... more In this paper, the elimination of harmonics in a cascade multilevel inverter by considering the nonequality of separated dc sources by using particle swarm optimization is presented. Solving a nonlinear transcendental equation set describing the harmonic-elimination problem with nonequal dc sources reaches the limitation of contemporary computer algebra software tools using the resultant method. The proposed approach in this paper can be applied to solve the problem in a simpler manner, even when the number of switching angles is increased and the determination of these angles using the resultant theory approach is not possible. Theoretical results are verified by experiments and simulations for an 11-level H-bridge inverter. Results show that the proposed method does effectively eliminate a great number of specific harmonics, and the output voltage is resulted in low total harmonic distortion.

Lancet

IEEE Transactions on Industrial Electronics, 2010

In this paper, the elimination of harmonics in a cascade multilevel inverter by considering the n... more In this paper, the elimination of harmonics in a cascade multilevel inverter by considering the nonequality of separated dc sources by using particle swarm optimization is presented. Solving a nonlinear transcendental equation set describing the harmonic-elimination problem with nonequal dc sources reaches the limitation of contemporary computer algebra software tools using the resultant method. The proposed approach in this paper can be applied to solve the problem in a simpler manner, even when the number of switching angles is increased and the determination of these angles using the resultant theory approach is not possible. Theoretical results are verified by experiments and simulations for an 11-level H-bridge inverter. Results show that the proposed method does effectively eliminate a great number of specific harmonics, and the output voltage is resulted in low total harmonic distortion.