Control of a Grid-Connected Photovoltaic Plant under Non-Uniform Insolation
Sr. Miguel A. Torres L., Postdoctorando Proyecto FONDAP SERC-Chile, LCDA – DIE.
A case study of a modular photovoltaic (PV) plant where PV panel arrays are connected
to the grid through cascaded single-phase current-source inverters is presented. It is
shown that, under non-uniform insolation conditions of the PV arrays, the output
voltages of the cascaded inverters become unbalanced. Therefore, a dc voltage
elimination control loop is proposed to balance the output voltage of the H bridges.
Additionally, a control technique called virtual synchronous generator (VSG) is applied
to the PV plant in order to support the control of the grid frequency emulating an
inertial response and providing damping and droop power. For the simulated cases,
the PV plant was always capable of performing the VSG functions, in spite of the
unbalance condition of the output voltages of the H bridges. However, when the
proposed dc voltage elimination control loop was in operation the maximum peak
output voltage and the amplitude of its fundamental component were reduced in
13.3 % and 27 %, respectively.