Research On Grid Connected Inverter With LCL Filter

Of high-power grid connected photovoltaic inverters, the parameter setting of traditional L filter is complicated, on the one hand, the parameter of L filter should be correspondingly decreased because of the increased power capacity and lowered switching frequency, on the other hand, the feasible parameter of L filter is limited by the fabrication of high-power reactor, the speed of response and the voltage drop of the reactor, fortunately LCL filter is the practicable way to avoid aforementioned contradictions. So, in this paper, the models of L filter and LCL filter were established both in stationary and synchronous frame, the principle and unique characteristic was analyzed thoroughly, a practical parameter design process was proposed, and the active and reactive damping method was debated later. The control strategy was promoted for the whole system, including the control of DC voltage as well as AC current. Taking into account of the utility gird faults, three related issues were discussed including the determination of the sequence component, balanced positive-sequence control and the implementation of the control strategy, after all, an unique low voltage ride through approach aimed at photovoltaic was proposed. Finally, a simulation model was created in PSCAD/EMTDC, the related theories, methods as well as strategies were confirmed with the simulation results, and the results also provided a reliable reference to the practical engineering.