A shunt hybrid active DC filter (HADF) is applied to eliminate DC transmission line current harmonics in HVDC transmission system. Since the harmonics increase transmission line losses and disturb control and monitoring equipments so HADF are used to suppress harmonics on DC transmission lines. In this paper a modified method is presented to control the shunt HADF which is not dependent on HVDC circuit parameters. HADF by injecting the compensating current to DC transmission line with the modified method suppresses the DC transmission line current harmonics significantly. Six major problems in design of modified control method have been discussed thoroughly. The principle of operation is described and the theoretical analyses are indicated to verify the control strategy. HVDC system is simulated by PSCAD/ EMTDC software. Simulation results and comparisons prove and validate the accuracy of these claims.

Abstract-This paper presents an Optimizat ion Sizing of a stand-alone PV/FC/Wind Hybrid System (PFWHS) to optimize the sizes of co mponents of PFWHS. Based on PSO algorith m, one optimal sizing method was developed to determine the optimal configuration of system that can achieve the load required power supply probability (Reliab ility) with a minimu m overall cost of energy (OCE).PFW HS costs involve investments, operation and maintenance as well as loss of load costs. The applied wind and radiat ion datasets belong to northwest region (Jolfa, latitude: 38_56, longitude: 45_ 37, altitude: 710, m) of Iran. In this paper the impact of availability of PFWHS co mponents is investigated on optimal sizing. So, to investigating the impact of component availability rate on PFWHS costs and reliability due to failure and repair rate of PFW HS components and uncertainty in wind speed and solar irradiance, t wo scenarios are considered. In first scenario the availab ility of all co mponents is considered 1 and in second scenario isn't considered 1 because of failure and repair rate of co mponents and uncertainty in wind speed and solar irradiance. Obtained results prove that while the overall cost of energy is optimized, the reliability indices are within a satisfactory bound with regard to the reliab ility standards. Also the results indicate that considering co mplete availability of components causes more reliability rate, so to achieve the actual behavior of PFW HS, the rate of co mponents availability must be considered in suitable insight to designer for supply the load.

The matrix converter is a new generation of power electronic converters and is an alternative to back-to-back converters in applications that dimensions and weight are important. In this paper, a simple control algorithm for a three-phase asynchronous motor based on a direct torque control technique, which is fed through a three-phase direct matrix converter, is presented. For direct matrix converters, 27 switching modes are possible, which using the predictive control technique and for the different modes of the matrix converter, the motor behavior is estimated at the next sampling interval. Then the objective function is determined and the optimal possible mode is selected. Finally, the best switching mode is applied to the direct matrix converter. In order to evaluate the proposed method, simulation of the system in Matlab/Simulink software environment is performed. The results show the effectiveness of the proposed method.