Three-Switch Common Ground Step-Down and Step-Up Single-Stage Grid-Connected PV Inverter

This article proposes the first three-switch common ground single-phase photovoltaic (PV) inverter which can support reactive power to the ac grid. The proposed step-down/step-up transformerless PV inverter totally eliminates leakage current and is suitable for use in any
on
- or
off
-grid applications which require active and reactive power support. The proposed converter also features a low number of active semiconductor devices, low voltage, and current stresses, acceptable grid side current quality, and high efficiency. The performance of the proposed PV inverter is evaluated for dc to ac single-phase grid connected inverter. The converter uses a direct power dead-beat controller in the inner loop which has a smooth, accurate, and fast response. Experimental results for a 500-W, 100
$V_{\text{dc}}$
, and 180
$V_{\text{dc}}$
to
$\text{110}\; V_{\text{rms}}$
prototype are provided in a closed-loop system in the presence of the proposed direct power dead-beat controller. The results from the prototype validate the theoretical analysis and the applicability of the proposed structure. The converter exhibits the capability for step-down/step-up dc to ac power conversion and demonstrates a peak efficiency of 97.5% and 96.8% in the 180 and 100
$V_{\text{dc}}$
, respectively.