Improving the safety operation of three-phase shunt active filter

Abstract

Power electronic based nonlinear loads produce harmonic currents that pollute the utility supply and create interference with other users, resulting in high total harmonic distortion and degrade the power quality. The generated harmonic currents can cause overheating of equipment and malfunction of protection systems. This indeed reduces performances for both energy consumers and providers. Therefore, active power filters are considered a viable solution to mitigate these disturbances. However, various current extraction techniques employed for the control of active power filters, often assume that the components of the filter are properly designed, or they have a slight effect on the performance of the control algorithm. This thesis aims to develop a design procedure for a three phase three wire shunt active power filter. The proposed approaches focus on the proper selection of the filter’s components, which caters for two design objectives. The first design methodology is to select component values based on the load current gradients. It allows selecting the minimum inductor values that enable the active filter to mitigate harmonics and improves the quality of the supply current. The second design criteria concern the selection of DC bus reference voltage, which allows determining the best value of DC reference voltage to enhance the performance of the filter under balanced and unbalanced load conditions and avoid excess energy loss in the system. Moreover, the thesis aims to present a protection scheme for the active filter to ensure the safe operation of the filter. The proposed system protects the shunt active filter against short circuit faults, voltage surges, and switching transients. The main protection devices used are overcurrent relay and metal oxide varistor. Furthermore, a control circuit of voltage phase sequence detection and grid frequency deviation are also investigated and presented in this thesis. Finally, the shunt active filter operation is analyzed for soft start and stop mechanism. The proposed filter uses a nonlinear current control algorithm developed to generate the reference currents of the active filter. The theoretical considerations are verified by simulation using Power System Blockset of Matlab/Simulink. The simulation results demonstrate the performance of the system and confirm the feasibility of the proposed procedures.

Date	28 Sept 2017
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Kamal Al-Haddad (Supervisor) & Abdelhamid Hamadi (Co-supervisor)