A PV inverter with charge-pump circuit topology

This paper proposes a photovoltaic (PV) inverter capable of stepping up voltage and the control algorithm for the inverter. The proposed inverter employs a charge-pump (CP) circuit instead of the commonly used step-up converter of a chopper type. Because the CP circuit does not include any inductor, the proposed inverter can be formed compactly. The CP circuit steps up the dc link voltage of the inverter by superimposing the voltage of the capacitor in the CP circuit on the PV voltage. So that the inverter performs the effective operation of the voltage step-up, the capacitor needs to maintain an appropriate voltage level. The equations modeling the energy variation of the capacitor are derived. Based on the equations, the maximum voltage step-up ratio of the inverter is obtained. The observation of the simulated output voltage waveforms of the inverter introduces two improved topologies of the CP circuit. The experiments using the inverter operated by the described control techniques confirms that the inverter can perform effective step-up operation while executing maximum power point tracking (MPPT) operation successfully.