| Popis: |
Zero voltage ride through (ZVRT), which is now mandatory in countries such as Germany and South Australia, improves the dynamic performance of wind generator (WG), mitigating outage risks in renewable energy-dependent power grids by preventing cascaded tripping. In the present work, enhancement of ZVRT for a permanent magnet synchronous generator (PMSG) based WG is studied. During ZVRT, grid power drops to zero, and machine side converter (MSC) power is transferred to the DC-link, causing large overshoot in voltage. In literature, a braking chopper (BC) has been used to enhance ZVRT of PMSG based WG. However, significant energy loss and heat dissipation associated with BC undermine its advantages. In the present work, during ZVRT, an interchange of converter control (ICC) between MSC and grid side converter (GSC) is proposed. This will lead to decrease in MSC power and thereby decrease in DC-link peak overshoot. However, this is not sufficient to restrict DC-link voltage within the permissible limit of 1.2 per unit. Therefore, an optimally tuned supercapacitor-based energy storage system (SC-ESS), connected to the DC-link through a bidirectional buck-boost converter (BBBC) is proposed to reduce the peak overshoot of the DC-link voltage and enhance ZVRT. An objective function is proposed to minimize DC-link voltage deviation during ZVRT with ICC, and the rating of SC-ESS. The optimization problem is solved using particle swarm optimization (PSO). The proposed method is compared with ZVRT enhancing methods like BC, SC-ESS, and ICC. The simulation results demonstrate that the peak overshoot of the DC-link voltage is least with the proposed method during ZVRT. |
