Abstract:
Z-source inverters (ZSI) have a unique ability to achieve single stage voltage buck-boost
operation for energy conversion. This thesis presents a three-level ZSI using a single LC
impedance network for photovoltaic (PV) application. The network is used between DC voltage
source (including PV array and a bidirectional buck-boost system) and neutral-point-clamped
(NPC) inverter to achieve the desired stepped-up and stepped-down output voltage level as per
the solar variation. Alternative phase opposition and disposition (APOD) modulation technique
with proper triplen offset and appropriate addition of time delay/advance is used to achieve the
required boost in DC link voltage. A traditional MPPT technique (Perturbed and Observed (P&O)
is used to introduce a shoot-through interval in switching waveform to extract the maximum
power from the PV panel. Traditional MPPT technique does not allow boosting the Z-network
capacitor voltage more than the maximum power point (MPP) voltage of the PV array. This
thesis presents a unified voltage control technique to track the MPPT and also maintains the
desired Z-source capacitor voltage level. The design, implementation and control of single
impedance network based multilevel ZSI for photovoltaic application with BESS according to
generation-demand is discussed. This proposed topology not only tracks MPPT output voltage
but also maintained constant output voltage with wide range of variation of insulation
(irradiance). To validate the proposed scheme the system is extensively simulated in
MATLAB/Simulink.
