Iman Ziari

A New Approach for Allocation and Sizing of Multiple Active Power-Line Conditioners

In this paper, a particle swarm optimization (PSO) algorithm is developed for allocation and sizing of multiple active power-line conditioners (APLCs) in power systems. The utilized objective function comprises four factors as total harmonic distortion, total size of active power-line conditioners (APLCs), harmonic transmission-line loss, and motor load loss. To evaluate the capability of the proposed method, the IEEE 18-bus test system is employed and investigated in three different cases. These cases are based on the assumption of continuous/discrete and limited/unlimited size for APLCs, requiring the optimization method to solve discrete/nondiscrete nonlinear problems. Therefore, in addition to PSO, an integer nonlinear optimizer (discrete PSO called DPSO) algorithm is also developed. Simulation results are compared with results obtained by genetic algorithm as well as with nonlinear programming (discrete nonlinear programming). It is demonstrated that analytical methods enjoy higher accuracy in smooth objective functions while they are not accurate enough in practical situations where nonsmooth objective functions are involved. If improper initial solutions are provided, achieving optimized results cannot be guaranteed by using analytical approaches. It is also shown that heuristic algorithms due to their randomness characteristics are more useful in practical cases where a number of local minima are present. Simulation results confirmed the capability and effectiveness of the proposed PSO-based algorithm in the allocation and sizing of multiple APLCs in a test power system compared with analytical methods and other heuristic algorithms.

Optimal Allocation and Sizing of Active Power Line Conditioners Using a New Particle Swarm Optimization-based Approach

Abstract Optimal allocation and sizing of active power line conditioners in a distribution network is a discrete and non-linear problem. Heuristic-based optimization methods are reliable approaches for solving these types of problems, particularly for a large-scale distribution network. However, the optimization parameters in heuristic methods can influence the final solution significantly so that if these parameters are selected improperly, the risk of trapping in local minima may be remarkable. In this article, a new method—modified particle swarm optimization—is proposed for optimal planning of active power line conditioners in a distribution network that is polluted by non-linear loads. In this method, external particle swarm optimization is used to determine the main particle swarm optimization parameters accurately. To validate the performance of the proposed method, a 6-bus and the IEEE 18-bus test systems are employed. Different scenarios are studied, and the results are compared with those obtained by other optimization methods, such as conventional particle swarm optimization, genetic algorithm, and discrete non-linear programming. The results illustrate higher accuracy of the proposed modified particle swarm optimization and its applicability for solving discrete and non-linear problems, such as active power line conditioner planning.

Using Active Power Filter Based on New Control Strategy to Compensate Power Quality

In this paper, a three-phase active power filter is presented to improve the power quality of a system which supplies a three-phase non-linear load. For this purpose, a three-phase voltage source inverter bridge with a DC bus capacitor is used as an active power filter. A new control strategy is proposed which is based on two popular strategies: synchronous d-q reference frame method & synchronous current detection method which have their own advantages and disadvantages. The proposed control strategy is based on both of two mentioned strategies in order to obtain a good accuracy as well as settling the current response to steady state value very quickly. A hystersis based carrierless PWM current control over the command currents of the active power filter is used to derive the gating signals. Computer simulation results are provided to verify the effectiveness of the proposed method.

Using Active Power Filter Based on a New Control Strategy to Compensate Power Quality

In this paper, a three-phase active power filter is presented to improve the power quality of a system which supplies a three-phase non-linear load. For this purpose, a three-phase voltage source inverter bridge with a dc bus capacitor is used as an active power filter. A new control strategy is proposed which is based on two popular strategies: synchronous d-q reference frame method & synchronous current detection method which have their own advantages and disadvantages. The proposed control strategy is based on both of two mentioned strategies in order to obtain a good accuracy as well as settling the current response to steady state value very quickly. A Hystersis based carrierless PWM current control over the command currents of the active power filter is used to derive the gating signals. Computer simulation results are provided to verify the effectiveness of the proposed method

Optimal placement of an active filter in a power system

Active filtering has now become a mature technology to compensate harmonics in power systems with nonlinear loads. This paper introduces an iterative algorithm to investigate the optimal determination of location of an active filter. The objective function includes minimization of transmission lines losses and total harmonic distortion. The 5 bus IEEE power system is used to evaluate the applicability of the proposed method.

A New Method for Modelling Loss in a Distribution Network

In this paper, a method is proposed for modeling the loss in power systems for the economic dispatch problem. It is based on the analysis of number of second order polynomial equations which model the loss so that by calculating the coefficients of these equations the loss relation is obtained which is the main objective. Using the noted equations and some load flows then curve fitting between them, the coefficients are calculated. A case study is used to evaluate the proposed method and the results are compared with the results of conventional B-method and those obtained by the load flow. The Accordance between the results of the proposed method and load flow shows the accuracy of the model. The method also enjoys simple equations and process and besides it is not as time consuming as some other methods.

Using Correced Criteria to Model Flashover Voltage of Polluted Insulators

In this paper, a dynamic model to calculate the flashover voltage of polluted insulators is presented. This paper focuses mainly on two points: the criterion of arc propagation and the arc length in which the flashover occurs. For first point, the typical criteria of arc propagation are not regarded but also the main criterion of arc propagation is used. For the second point, a computer program is used so that the obtained results show that the flashover occurs when the arc bridges about 67% of the insulator length. To evaluate the proposed method, four sample systems are considered and the flashover voltage for different surface conductivities and ESDDs is obtained. The results based on the proposed method are compared with those of three proper methods. The accordance between the acquired results shows precision of the method

A new method for modeling loss in distribution network

In this paper, a method is proposed for modeling the loss in power systems for the economic dispatch problem. It is based on the analysis of number of second order polynomial equations which model the loss so that by calculating the coefficients of these equations the loss relation is obtained which is the main objective. In order to determine these coefficients, first the loss curve for each unit is obtained while the real power output of the noted unit is changing and the output of the rest of units is constant. The same as this procedure is implemented mathematically and one second order polynomial equation for each unit is acquired. Using curve fitting between these curves and the equations, the coefficients are calculated. Two case studies are used to evaluate the proposed method and the results are compared with the results of conventional B-method and those obtained by the load flow. The accordance between the results of the proposed method and load flow shows the accuracy of the model. The method also enjoys simple equations and process and besides it is not as time consuming as some other methods.

Using Corrected Criteria to Model Flashover Voltage of Polluted Insulators

In this paper, a dynamic model to calculate the flashover voltage of polluted insulators is presented. This paper focuses mainly on two points: The criterion of arc propagation and the arc length in which the flashover occurs. For first point, the typical criteria of arc propagation are not regarded but also the main criterion of arc propagation is used. For the second point, a computer program is used so that the obtained results show that the flashover occurs when the arc bridges about 67% of the insulator length. To evaluate the proposed method, four sample systems are considered and the flashover voltage for different surface conductivities and ESDDs is obtained. The results based on the proposed method are compared with those of three proper methods. The accordance between the acquired results shows precision of the method.